Part Twelve – Minor Disaster Strikes

This twelfth entry was published originally by JSHarris on the 19th August 2013 and received 1,249 views on the closed forum

I just knew I shouldn’t have made that quip about fracking last week. It was stupid. In fact so stupid that it’s deeply offended the gods who look after our environment (who clearly don’t have a sense of humour). They’ve decided to teach me a lesson………….

Just after posting the last entry I had a call from the drillers. A neighbour had reported air bubbles blowing up through the bed of the millstream, some distance from the borehole. The drillers were using compressed air to blow the cuttings out and it seems that down at around 15m or so they hit a fault in the gault clay, a fault that’s hydraulically connected to the stream, most probably through a subterranean spring that normally flows water into the stream bed. It seems this compressed air overcame the water pressure at this depth and forced its way up through the stream bed, some 30 to 50m from the borehole position.

The drillers thought they could fix the problem by sticking more casing down the hole (only costs me £35/m……). We thought this had worked, but today when the drill rig started up the stream turned black with liquefied gault clay being blown through the fault. This has caused us to abandon this borehole at a depth of 21m and take the best part of £3k in lost cost.

The plan now is to bring a bigger rig on to site tomorrow or Wednesday and drill a new borehole in a different location, one that will (hopefully) not be hydraulically connected to the stream. We’re moving further away from the stream, to a location where we’re hopeful that there won’t be any springs underground. The bigger rig will be able to sink a longer length of casing in the bore, though, so even if we do hit problems the hope is that the casing will seal off any leaks.

The other hit we’re taking is by having to abandon the water pipe duct we’ve put in under the foundation. The new borehole location is the other side of the site, so we’ll need to dig a new trench and stick another length of ducting in.

Still, the good news is that the new brickie and renderer I’ve found are a fair bit cheaper than the original quote, so I’ve saved a bit on this that’ll help cover the extra borehole cost.

It’s a bit like Russian roulette this drilling game………………..

 

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Shah 21 Aug 2013 04:39 PM :

 

Sorry to hear that JSH. That is building work. **** happens the moment you mention the project is running smoothly.

 

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jsharris 21 Aug 2013 06:04 PM :

 

Thanks, I’m now expecting the worst, and planning for what might happen if the second borehole fails as well……………..

The bigger drill rig is now on site, set up and drilling, so the critical time will be around mid-morning tomorrow when it hits the depth where the other rig had problems. The first borehole was over by the right-most pole in the photo of the model at the top of this blog, the stream runs along by the tall hedge at the bottom. The new borehole is up by the retaining wall, towards the back of the garage base, so a lot further away from the millstream.

 

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ProDave 22 Aug 2013 07:36 PM :

 

So did you make progress today? or did you have further trouble?

 

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jsharris 22 Aug 2013 08:30 PM :

 

Fingers crossed……………………………..

The drilling’s going slower than hoped, but so far there’s no blow through to the stream. The drillers are chucking extra casing down as a preventative measure, but this slows drilling down, as they have stop every couple of metres, pull the whole drill string out, swap the drill string for a length of casing, which means unscrewing each length of drill pipe to separate them into short lengths, then threading another length of casing on to that already down the hole, then pushing the casing down to drilled depth, then dropping the drill string down again, threading all the lengths of drill pipe on one by one.

The rig will drill at a rate of a metre every ten minutes or so, but it takes at least 4 or 5 times as long to keep pulling the string, sticking more casing down and then dropping the string back down the hole (if you’ve watched “Black Gold” on TV then you’ll have a feel for the process – this is pretty much the same, except we have to stop and add casing every couple of metres).

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jsharris 23 Aug 2013 06:20 PM :

An update. Our luck (and that of the drilling company) seems to be following it usual course of things going wrong. The drill rig broke earlier, and needs a replacement valve from Italy, which has a ten week lead time. These things happen, though, and it’s no one’s fault, just bad luck. They’ve taken the defective parts off site and are going to see what they can do to fix things next week, but there won’t be any further drilling for at least a week, maybe longer, whilst they sort out an alternative way of drilling our hole.

It looks as if I will have to delay the house delivery until I can be reasonably sure that the rig is going to be off site, not really a problem, as we’re not in any great rush to finish the house, just a bit of an exercise in replanning the programme and sorting out things like a temporary water supply for the guys who will still be working on site. I rang around to see what the cost of a hired water bowser would be – they are silly money for what they are, like around £130 a week. As I can buy 25 litre containers for around a fiver, that’s what I’m doing. It’s no hardship to just lug five or six of these over to the site in the back of the car every time I go over and I reckon the guys I have doing some stone work and rendering should be able to get by on 100 to 150 litres of water a day.

Looks like I need to keep the fingers of both hands crossed from now on.

 

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Part Eleven – Fracking……….. (Only Kidding)

This eleventh entry was published originally by JSHarris on the 15th August 2013 and received 1,197 views on the closed forum

Just a short entry this time, as we had a quiet week last week. The brickie that was scheduled to stick up a Bradstone boundary wall on top of our retaining wall (which is the boundary with the neighbour) first delayed a couple of times, then earlier this week cried off altogether, as he’d had an offer of a 6 week job elsewhere. This left us in the lurch a bit, as that boundary only has a bit of temporary fence on top of a 2.5m drop. I think I’ve found another brickie and labourer team who can start in a week or so, though, so we should get the wall done, albeit later than we wanted.

This week’s excitement got off to a good start when the drill rig turned up on site, with all the usual hassle involved when we block the lane for ages while unloading heavy plant. We have one very friendly local chap who always stops for a chat when walking past with his dog (I think he’s one of those people who just likes to chat for hours). When the rig was setting up he was chatting away, full of questions, and I was busy trying to get on with checking dimensions around the site, making sure the rig was in the right place and a dozen other jobs, so, in a moment of impatient mischievousness I told him that I was just about to put the Cuadrilla signs up on the gate as we were drilling and fracking for shale oil. Within half an hour I had a visit from another prominent local, full of indignation that there was going to be an oil well drilled in the village. Took me longer to explain that it was just a water borehole we were drilling, and that my comment about fracking was just a joke, than it would if I’d spent half an hour earlier just chatting to the bloke with the dog…………….

Here’s a picture of the drill rig:

And a boring one (awful pun intended) I took looking straight down the hole:

The drill rig sill be on site for another day or two, fingers crossed that they find water…………………

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 ProDave 15 Aug 2013 10:08 PM :

Telling your locals you are fracking, was probably on a par with joking with airport security “What do you think is in my bag, a bomb?”

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 jsharris 16 Aug 2013 08:23 AM

 You’re absolutely right, but at the time I was in a bit of a rush trying to make sure the drillers weren’t going to get held up by me doing last minute check measurements, and this chap (nice as he is) does like to chat away non-stop for hours if you let him. With hindsight I should have guessed that my weak attempt at humour would backfire, but all’s well now. Last night I had a couple of neighbours come up to me and joke about when we thought we’d hit oil, and talking to the drillers they’ve had more of the same from passers by.

The blue/black gault that they’re drilling through at the moment seems full of fossils, some quite nice. There’s also some odd-shaped hard lumps of lighter looking fossil coming up, so I did a search on what was likely to be found in Cretaceous gault. According to Wikipedia:

“Gault often contains numerous phosphatic nodules,some thought to be coprolites and may also contain sand as well as small grains of the mineral glauconite. Crystals of the mineral selenite are fairly common in places, as are nodules of pyrite.

Gault yields abundant marine fossils, including ammonites (such as Hoplites, Hamites, Euhoplites, Anahoplites, and Dimorphoplites), belemnites (such as Neohibolites), bivalves (such as Birostrina and Pectinucula), gastropods (such as Anchura), solitary corals, fish remains (including shark teeth), scattered crinoid remains, and crustaceans (such as the crab Notopocorystes). Occasional fragments of fossil wood may also be found.”

The odd-shaped lumps seem to me to be what’s described above as “phospatic nodules”, so I looked up “coprolites”. Rather unpleasantly these seem to be fossilised animal poo, maybe from dinosaurs (the stuff we’re drilling through was laid down around 100 to 146 million years ago). In the hope it might be good for the garden after all these millions of years I’m piling it up in a corner…………….

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 joiner 16 Aug 2013 11:20 AM

 Yeah, right!

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 jsharris 16 Aug 2013 11:51 AM :

 It seems that using 100 million year old dinosaur poo as fertiliser is now the least of my problems. I was called over to the site first thing by the drillers, as they’d hit a problem. They’re drilling with compressed air to blow the cuttings out of the hole, and when they hit a depth of around 20m yesterday afternoon they were made aware that there were bubbles coming up in the stream and a pond further up the valley.

It seems the hole has hit a fault and compressed air is making its way deep underground (presumably via some of the springs that abound around the area) and into the stream. The director of the borehole company drove up this morning to look at the problem and they are now trying to add more casing to try and seal up around the hole and stop the air getting out. The air won’t cause any problem, but they are worried that it will blow some of the gault clay that they’re drilling through into the springs, which will then turn the stream black. Although this wouldn’t be harmful to the environment (it’s only ancient mud and the stream is too small at this point to have much in the way of fish in it) the fact that it is highly visible in what is a crystal clear chalk stream is bound to get the Environment Agency wound up within hours, and the last thing we need is them on our backs.

We’re keeping our fingers crossed that the extra casing does the job. They’ve put in as much casing as the small rig they have on site can handle, so if this doesn’t fix it then they’ll need to swap rigs for a bigger one, which will add a three week delay.

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ProDave 16 Aug 2013 02:56 PM

 Ah, so you ARE fracking after all ! (I’ll get my coat)

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 jsharris 16 Aug 2013 05:08 PM:

 Actually, it’s a damned good illustration of the risks that fracking presents. We were blowing air up in the bottom of a stream around 50 to 60m away from where we’re drilling, and across the other side of a lane. Our drill obviously hit an unforeseen crack in the heavy gault clay, something the the hydrogeologist didn’t even think was possible. I’ve just come back from the site and the extra casing down the hole seems to have done the job for now, as they’re back drilling again, with no sign of anything coming up in the stream.

One unpleasant consequence of this is that overnight the water from the stream flowed back though this fault and filled the borehole, turning the clay cuttings into thick, black porridge, that the drillers are trying hard to drill out. As you can imagine, this is an unbelievably messy job. This black and slimy porridge of clay is being blown out of the 8″ hole by a 600 cfm compressor. It looks for all the world as if we’ve hit a gusher of oil, with this black stuff shooting into the air and raining down everywhere. I think I’m going to have to look at getting a minidigger in to dig a ditch for the stuff, as at the moment it’s around ankle height all over that end of the site.

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 Pr

How deep have you gone? and how deep do you expect to go before you reach decent water that you can drink?

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jsharris 16 Aug 2013 09:10 PM

 So far we’re only at around 25m, target depth is 55m. The hydrogeologists report reckons that we should have to go through around 35 to 45m of this nasty gault clay (which is normally considered to be an aquitard, a waterproof sealing layer) and then we should hit a thin (around 6 to 8m thick) bed of running greensand, which is water bearing. The water down in this greensand is ancient, hundreds, perhaps thousands, of years old, as it’s trapped underneath the thick layer of gault clay. The prognosis is that the borehole should be able to deliver 4 to 6 cubic metres an hour, far more than we’ll ever need (we probably don’t ever need more than 1/2 cubic metre per day). It also suggests that the water quality will be high, and that we probably won’t need to do any treatment on it (although we’ve budgeted for a filter and UV treatment unit).

So far the hydrogeologist has been reasonably accurate in terms of the strata and the probability of their being hydraulic continuity between the stream and the borehole location, but he’s seriously confused by the fact that we blew compressed air through an apparent fault at around the 15m depth point, as there’s no indication that this could happen (it’s the thing that worries me about fracking, do the geologists REALLY know what the risks of groundwater contamination are?).

At a push we could just use the stream water and treat it. It comes from several springs just a few hundred yards up the valley, and is a typical chalk downland stream, sparklingly clean. We seem to have a connection from the stream to the borehole at around the 15m depth point (perhaps because we’ve intercepted an underground feeder spring), so the fall back would be to just line the bore and add a filter pack.

If we get to target depth, then we will seal and line the hole down to the lower greensand (to keep out the water from the higher levels) and just stick a glass media filter pack at the bottom to keep the sand out and give us a pretty clean source of water.

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joiner 21 Aug 2013 07:59 PM :

 All of this confirms people’s fears over fracking.

As you say, J, no one can tell with total accuracy what’s down there and given the pressures that fracking exerts, far in excess of anything you’re putting down there, then a fault a many times the size of yours (especially when deliberately enlarged to release the trapped deposits) has the potential to cause irreversible damage.

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jsharris 22 Aug 2013 09:02 AM :

 From what I can gather, the statistics from the US seem to put the risk of ground water contamination or significant disturbance (i.e. reducing the height of the water table) from fracking at around 7%. That’s largely due, perhaps, to the cavalier approach to this in the US, but there are some real horror stories out there connected with recent fracking activity. The pro-frackers argue that the process has been used since the 1930’s, but they neglect to point out that horizontal drilling and fracking is a new process, and one that seems to have a much higher risk of disturbance to deep geology. I think the other major issue is that the UK is far more densely populated than the US and has a much greater reliance on underground aquifers for its water supply. For example, if fracking polluted the chalk aquifer that supplies much of the water for the south and south east of England,then alternative water supplies would have to be found for many millions of homes. This makes the UK a far riskier place to use this technology than the US, where the impact might be just a single large town losing its water supply (as happened at Barnhart, Texas, recently).

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Part Ten – Out Of The Ground

This tenth entry was published originally by JSHarris on the 2nd August 2013 and received 1,302 views on the closed forum

At last we’re done with ground works until we do the drive and landscaping, after the house and garage are up. Pretty momentous occasion, really, as everyone I’ve spoken to seems to reckon that most of the build risk is associated with getting out of the ground. I think we’ve been lucky, in that despite the complexity of the ground work, we’ve not had any cost over runs at all. Part of that luck has to be the weather, we were blessed with the hottest, driest spell we’ve seen for years, which kept the anticipated water problems at bay.

I had a few last minute panics, for example when the stone supplier for the new boundary wall told us at the start of the week that there was an 8 week lead time. Bit of a problem when the contractor was planning to be off site by the end of the week. We’d hit the same problem with lead times for even off-the shelf stuff over the past couple of weeks. It seems the building trade has suddenly picked up and the builders merchants are struggling a bit. The internet came to the rescue, just as it had when trying to get pipe fittings a couple of weeks ago, and Simply Paving (yes this is a plug for them) not only agreed to supply within two days, but gave a better price and free delivery into the bargain. I was able to buy the Bradstone we wanted retail at a better price that my ground works chap could get it trade via the builders merchant, in fact about 20% better (the price I paid inc VAT was nearly exactly what he was quoted ex-VAT, with an 8 week lead time). I’m increasingly forming the view that builders merchants need to get their act together if they want to survive. The internet companies are gradually expanding into the builders merchants traditional market, and offering better value and fast delivery. The only slight downside of me buying the stone was that it added another big receipt to my VAT reclaim pile.

The other main problem this week has been a personal one, it seems someone has tried to steal my identity to get a loan. This came to light during a credit check, and thankfully hasn’t caused too much of a problem, other than me wasting hours trying to track down the details via the credit reference agencies. It seems to have been a failed attempt at ID theft, but it has left a trace on my credit history showing a credit check for a loan that I didn’t take out. Whether this will be easy to get removed remains to be seen – I can say it is a very time consuming process trying to get to the bottom of stuff like this.

Anyway, here’s a couple of pictures of the house base, just to show we’ve been doing something this week:

This compacted layer of stone will be covered with a thin layer of 8mm stone, then will have 300mm of expanded polystyrene foam (EPS) laid on it. The house foundation reinforced concrete ring beam and floor slab, with integral UFH pipes, will be cast into the EPS insulation. It’s a nice and simple system for a location like this, no deep trenches or piles, the house literally just sits on the ground on a thick layer of foam.

We’ve put in an access track, more or less where the drive will go, albeit with a bit of steeper initial slope, as we wanted to create a flat working area in front of the house that was relatively mud-free. The track is a 300mm thick (more in parts) layer of reclaimed crushed concrete. Rough old stuff, but it should take the wear and tear from trucks for a few weeks and hopefully provide a soakaway area to catch the inevitable muddy run-off when it rains. The sub soil here is a very solid clay, that when dug and broken up turns to fine dust, when this then gets wet it turns into horribly sticky clag, so we want to try and keep the working areas around the house as clear of it as we can. Much of this crushed concrete will have to be dug out and removed when we come to lay the drive, but the cost is just something we’ll have to accept to make life tolerable on site in the wet.

Here’s a photo of the temporary access, partially blocked by a truck delivering stone (why do stone and block suppliers use daft tail lift trucks like this?):

That’s all for this week, I’m off to have a cold beer! Next week will be a bit quieter, as I just have a couple of brickies on site building a boundary stone wall, plus (if they keep their word) the DNO installing the new electricity connection to the meter box I’ve put in.

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 Jamiehamy wrote on 2nd August 2013:

Loving the updates and especially the pictures to bring it to life. Enjoy your beer, you deserve it!

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 JSHarris wrote on 2nd August 2013:

Thanks Jamie.

It’s was bit of a roller coaster ride today, I was up at 06:30 sending last minute emails this morning, worrying that the stone wouldn’t arrive on site before the ground works guys had to take their digger and block grab off site, leaving me with no way of unloading the truck. The stone delivery driver was supposed to give me a call to say he was an hour away, but his office hadn’t passed on my number.

Luckily the driver found the site. We have a recurring problem with delivery drivers either not being able to find us, or not bothering to read the route and access instructions we send out to every single company, with every order. The lanes either side of the site are single track and very restricted access, even something the size of a Transit would struggle to get down them, so we direct everyone in via a specific route past the old mill. It’s still narrow (around 3m wide) but at least we know that even a pretty big artic can get in that way.

Tomorrow will be a site tidy up day, with me making sure all the security fencing is back up tight and secure, the signs are all back in place and the stuff is all sorted ready for the brickies arrival next week.

After a bit of stress and tension at the start of the day, I’m now back to feeling pretty comfortable about the way things are going. There’s a certain sense of achievement in seeing something you’ve designed and drawn up turn into reality.

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 Oz07 wrote on 4th August 2013:

Where’s those wheel cleansing facilities you promised!?

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 Jsharris wrote on 4th August 2013:

Ahhh, that’s where you need to check to see what I actually promised!

The planners wanted me to “provide details of a scheme for washing of construction lorries’ wheels on leaving the site…..”. BUT, what I offered to do (and what was accepted by the planners as fulfilment of the condition) was:

“Before any vehicle leaves the site it shall be checked for mud and spoil on the tyres and if required the tyres will be cleaned using a brush, jet wash or other suitable means………….”

So, I didn’t actually promise to provide wheel cleansing facilities unless they were found to be needed following an inspection. We deemed that they weren’t required, because none of our inspections showed a need to clean any vehicle wheels. Simples…………..

Planning seems to often be about gamesmanship, and this was a classic example. The planners asked for details, I gave them a proposal, they accepted it. Not my problem that they didn’t notice that my offer didn’t include provision of vehicle tyre washing unless it was found to be necessary. We didn’t think it was necessary, as no vehicle had mud on its tyres when it left the site, in our view.

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 Oranjeboom wrote on 26th April 2016:

 Hi Jeremy,

I tried to PM you…inbox full I guess? In any case, this way others benefit also.

Hoping to borrow your ideas on UFH within the concrete slab. Seems this is a mysterious ‘new’ thing when I discuss with the professionals (“stick to separate concrete and screed layers…simpler and cheaper” Really???).
In the retrofit part of my build, for the old bungalow, the original plan was to have a retrofit UFH system on top of the old (uninsulated slab).

I have now decided to rip up the plan (and the old slab) and go for 150mm PIR in the bungalow (I could go more depending how the ‘big dig’ goes). But rather than having a slab plus a final screeded UFH slab on top, I would like to go for your approach of just having one slab (with UFH). I’d like to have as much insulation in there as I can, but am limited to how deep I can dig, but this is my plan:

15 Bonded Bamboo flooring
100 Concrete (with UFH) With 25mm perimeter insulation.
150 PIR (possibly more)
DPM
25 EPS sacrificial layer
100 hardcore with sand blinding

Verbally my BCO okayed the idea last week, but I need to send him the detail in order for him to ‘approve’. Do you have any slab detail that you could send me? I won’t be forwarding this to him, but may just ‘borrow’ some of the detail. I’ve checked your blog but could not locate much (searching doesn’t seem to limit to your blog or at least ‘hit’ anything). It’s a good read though, and at least show’s that I’m not the only one with screw-ups along the way!!

I also have some specific questions, if you have time:
1) Did you install mesh in your concrete? I think you ring beamed it all….. I’ll only need a small piece of mesh where my staircase will go I think – nothing else is going to be built on top of it.
2) At what height did you have your UFH within the concrete slab and did you fix them by way of mesh or by other means? Clipping direct onto the EPS will mean a bigger response time, but less tricky to lay I guess.
3) What type concrete did you use?
4) Did you power float the slab to get a level(ish) surface?

On cold spring (winter!!) days like this, I am determined to get as much insulation in where I can!!

Thanks Jeremy! Back to my ‘to-do’ list/book!!

Rgds,

OB

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 Jsharris wrote on 28th April 2016:

 Hi, sorry for the delayed reply, my inbox here constantly fills up with people who ask questions by PM yet never post of the forum……………..

My view is that, with a thin (100mm steel reinforced) slab there’s no point in adding more work and cost by fitting UFH in another layer. Our UFH pipes are just cable tied to the slab steel reinforcement steel, on 200mm centres, with the pipes around 40mm below the top finished surface. It works extremely well, and is surprisingly quick to respond to changes, too.

We do have a ring beam around the edge, 200mm deep, with additional steel, and also across the slab where two internal load bearing walls rest. There are no UFH pipes in the ring beam or strengthened sections, where we needed to cross them we fed the UFH pipes through a door opening, as you would with a screeded system.

The steel fabric in our slab is set ~ 45mm above the EPS, and the UFH pipes are cable tied to the sides of the steels, so are around 40mm below the surface in practice (they are 16mm pipes, 2mm wall thickness.

The concrete is C35 readymix, fairly wet with good pourability, to make it easy to spread and poker. It was roughly trammelled level, using the upstand edges of the EPS slab L sections as levels, and then left to semi cure for around 5 to 7 hours and power floated dead flat and smooth. It ended up dead flat, the tiler that fitted the Travertine stone spent 40 minutes with his laser level trying to find the highest spot to work out from and couldn’t find one. He reckoned the whole slab was level to within about 1mm.

Being this level was a massive benefit when laying both the stone and the bonded down bamboo, as it meant only a thin layer of adhesive was needed and getting things dead flat was simplified by having such a flat slab to start with.

Our basic slab spec is that there are L shaped edge edge pieces of EPS that are 200mm deep under the ring beam, 400mm deep at the sides, and 200mm wide under the outer section of the walls. The centre insulation is made up from three layers of 100mm EPS, with the DPM sandwiched between the top layer and the lower two layers. Under the EPS is a layer of grit blinding, over a 150mm deep layer of clean crushed stone.

I hope the above helps. As I’ve written elsewhere, just having the UFH circulation pump running, circulating water around from warmed areas of teh slab to shaded areas makes a massive difference to comfort level, as it evens out the floor temperature just for the cost of the 20W needed to run the small circulation pump

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Oranjeboom wrote on 29th April 2016:

jsharris, on 28 April 2016 – 11:13 AM, said:

Hi, sorry for the delayed reply, my inbox here constantly fills up with people who ask questions by PM yet never post of the forum..

That’s the problem of being a guru Jeremy. I try not to be too much of a lurker myself. I think some people are too reluctant to post stuff publicly and some people are just too lazy to search the forums on things that have been said/asked before.

Thanks for the detailed response – certainly useful info that others will hopefully stumble across too at some point.

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jsharris, on 28 April 2016 – 11:13 AM, said:

Our UFH pipes are just cable tied to the slab steel reinforcement steel, on 200mm centres, with the pipes around 40mm below the top finished surface.

The A142 stuff or similar? Yes, I didn’t want my pipes at the bottom of the slab, so this sounds like the way to do it when not using a thinner 75mm screed layer.

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jsharris, on 28 April 2016 – 11:13 AM, said:

and the UFH pipes are cable tied to the sides of the steels, so are around 40mm below the surface in practice (they are 16mm pipes, 2mm wall thickness.

Did you use any particular branded piping system?

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jsharris, on 28 April 2016 – 11:13 AM, said:

The concrete is C35 readymix, fairly wet with good pourability, to make it easy to spread and poker. It was roughly trammelled level, using the upstand edges of the EPS slab L sections as levels, and then left to semi cure for around 5 to 7 hours and power floated dead flat and smooth. It ended up dead flat, the tiler that fitted the Travertine stone spent 40 minutes with his laser level trying to find the highest spot to work out from and couldn’t find one. He reckoned the whole slab was level to within about 1mm.
C35…thought I had read that somewhere. My only worry about this whole approach is using concrete and not getting it pretty level. I will have to hunt an expert for that job I think! 9 rooms to do not including hallways etc with the biggest being 11m x 6.

Did you/pokerguy have any issues with the pokering and UFH pipes? Guess as long as it’s all secured nicely, there should not be any problems….apart from walking on the mess whilst pouring the stuff in!

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jsharris, on 28 April 2016 – 11:13 AM, said:

As I’ve written elsewhere, just having the UFH circulation pump running, circulating water around from warmed areas of teh slab to shaded areas makes a massive difference to comfort level, as it evens out the floor temperature just for the cost of the 20W needed to run the small circulation pump
Had not read that (yet) but a great tip. I’ve got some oversized floor to ceiling windows and sliding doors in the ‘south wing’ so hopefully that will warm up the slab nicely in the winter months (And cold April/May days!!!) to allow me to distribute that elsewhere.

Thanks for the useful info. Will run it past the BCO and then start digging out my 87sqm….

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 Jsharris wrote on 29th April 2016:

 In order:

Yes, the layer of steel fabric in the slab was indeed A142, 200mm x 200mm x 6mm diameter. It was stood on (I think) 45mm chairs like these: http://www.lemon-gs….te-spacers.html

We used the most flexible UFH pipe we could get, not the Pert-al-pert stuff that’s stiff and holds bends, because that stuff stuff gets easily damaged and dinged if it gets stood on where it runs over a bit of steel. I can’t remember the brand, but it was the multilayer stuff, 16mm OD, 2mm wall thickness, most probably this stuff: http://www.theunderf…ng-barrier-pipe

With a nice wet mix it will flow well, and a vibrating poker won’t be at risk of damaging the pipes. Get a long trammel (we had a monster aluminium one around 8m long) to drag the the top roughly level and let gravity do it’s thing after it’s all been pokered and trammelled. Being a wet mix it will almost self level anyway. This is what our slab looked like after being trammelled but before being power floated:

You just walk around in the concrete then wash your boots afterwards. You can walk on the steel mesh, so you’re only walking in a couple of inches of the stuff. There are no real risks when pouring and levelling, as long as the concrete mix is wet with a lot of slump, so it spreads freely.

Hope this helps, feel fee to ask any more questions. I can say that the UFH heat re-distribution system is brilliant, really, really effective at moving heat from sun-warmed areas to cooler areas.

Part Nine – Bloody Services…………

This ninth entry was published originally by JSHarris on the 27th July 2013 and received 1,962 views on the closed forum

Another week has passed, with the usual crop of frustrations. Funny old thing, but 99% of the hassle comes from one company, the DNO. The local chap is great, bends over backwards to be helpful, but the company as a whole couldn’t organise a piss up in a brewery.

The saga this week involved getting the electricity connected and getting a ‘phone line moved (which is on an electricity company pole). Readers may recall that I paid a fairly hefty sum to the DNO to get cables relocated and a pole moved (over £3500, and we ended up digging the hole for their pole for them, as they couldn’t get a digger to the site). Part of the arrangement was that at the time of sorting out the job (for which we had to pay upfront, in full, back on April 24th) the DNO would notify BT Openreach that they were moving a pole that had BT wires on. The system is supposed to work like this:

1. You set up a job with the DNO and pay upfront in full.

2. The DNO give you a date for the work, so you can get all the trenches dug, ducts laid etc.

3. The DNO turn up and move cables etc, and make new joints where required, including the new supply connection to the new house.

4. The DNO then send an ODNR notification to BT Openreach, confirming that the new pole has been erected and is ready to accept the BT cables.

5. The DNO issues an MPAN number to the client (me) to allow a supplier to be booked to install a meter.

Sounds easy, doesn’t it?

The first flaw is that the job isn’t handled by one team, or even as one job. The DNO takes forever and a day to organise themselves and they have a massive lead time for everything. After two months we finally got the new cable in place, followed a week or so later by the jointing team, to make the new connections. When I went to site this week I discovered that they hadn’t put the joint in for the feed to the new house, although they had done all the other work.

So, I called my helpful local engineer, who said he had that job booked in for the 8th August (WTF can’t they do all the jointing in one go?). I rearranged the programme to accept the delay in getting power on site, then got a call from my helpful local engineer telling me that he couldn’t do the new connection as a job hadn’t been raised. Knowing full well that it had, I tried calling the programming office. The phone just went unanswered…………..

Finally I got hold of their head office, who also couldn’t contact their programming office, but who did promise to try and sort things out. Finally, another one of the local helpful engineer brigade called, telling me I’d not paid an invoice for £393. I’m meticulous when it comes to filing, and I even file the envelopes as proof of posting date, so I checked and told him that I definitely hadn’t had an invoice for this sum. He read out what was on his screen, which was for a commercial supply. I read back to him the domestic connection form I’d filled in. Being a helpful chap he went off and promised to check, then called me to say that the invoice (that I didn’t receive) should have been for £265…………………. He emailed me a copy, so I could transfer the money to them pronto, and he must have put a rocket up the backside of the finance team, as they called me as soon as the money arrived to tell me they’d be issuing an MPAN number and that the job could go ahead as scheduled.

So, I then call the same company (but the supplier side, rather than DNO side) to tell them this, as the two parts are not allowed to talk to each other. They tell me that there’s currently a 4 to 6 week lead time on getting a meter installed……….. Arghhhhhhhhhhhhhhhhhhhhhhhhhhhhhh!!!!!!!!

So, when the head gets installed on the 8th August I still won’t be able to get power on to the site until mid-September. Bearing in mind that I first asked the DNO to quote for this work in February, and that I paid the only invoice they sent me in April, I’m not overly impressed. I bet the big boy house builders don’t get buggered around like this.

Not much point in me installing the meter box in the wall for the time being, I may stick it in next week, ready for the supposed connection date of the 8th.

I fitted a 100A DP lockable isolator in the meter tails in the end, as I wasn’t absolutely certain that the supplier would fit one of the Siemens meters with the built-in isolator. Easier to just flick a switch than use the screwdriver slot thing on the meter, anyway, and very useful to be able to isolate all the electrics at source. The small CU is just providing a current protected feed to the weatherproof outdoor CU box that supplies the garage, borehole pump, 16A builders supply and treatment plant (the outdoor box has RCBOs). It was cheaper to do this than run 25mm² SWA from the Henley block out to the outdoor CU, as I can now get away with just using a bit of spare 4mm² SWA for that run with the MCB in the meter box limiting the cable fault current. I just hope the DNO/supplier doesn’t have a whinge at me taking up too much space in the box.

Not that much has changed on site this week, despite a lot of work. I had a site meeting with the builder, all the way from sunny Tipperary, who was happy with the site and couldn’t see any problems from his side. He reckons the build may only take four or five weeks, which seems pretty quick, as it includes laying the foundation slab and erecting the house and garage. I know that building a factory manufactured panel system house is quick, but I’d thought that the build time was likely to be around 8 weeks. We shall see.

Finishing off from last weeks tale, it took all week to get the retaining wall up to finished height, and now all the big blocks are laid and concreted in. There are three courses of ordinary 100mm blocks to go on top of the wall along the north face, topped with a 600mm timber fence. That’s going to take a while, though, as we found out this week that there’s a 4 week lead time on the reconstituted stone that we’re using to face the neighbours side of the 100mm block wall (our side will be flush with the existing block work and will eventually be rendered).

This is how it looked at the end of the week:

We’re going to have a pretty impressive walled garden when it’s finished, should be a nice little sun trap.

Next week should see the rest of the site levelled, the base for the garage being laid and the access track being put in (at the moment the access track is under the big pile of earth). The house base will be excavated out another 150mm and a layer of compacted stone put in to act as the foundation. With a bit of luck, the ground works guys may be off site by the end of next week (although I think that’s a tad optimistic) so I can get the borehole driller in. I’m hedging my bets on the programme, though, and allowing two weeks before the driller gets

 

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Joiner wrote on 28th July 2013 at 08:01pm

 Is that your neighbour’s roofline above the wall?

It’s easy to relate the site to the model because of that lone tree!

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Jsharris wrote on 28th July 2013 at 08:17pm

Yes, it’s a bungalow sat higher up the side of the valley, and some distance away.

We won’t have any windows facing that way, and the gutter level of our roof will be around the level of the retaining wall as it is now, so all they’ll be able to see is the top of our roof ridge, and we won’t be able to see their house at all.

The neighbour up there has been tremendously supportive, and as a freebie I’m arranging for our “temporary” borehole standpipe to be permanently located right on their hedge line, as they have a veggie plot just over the hedge to the east (middle extreme right on the model photo). This will give them a free water supply for irrigating their veggies in dry weather, and won’t cost us anything (no water rates and the PV will be more than enough to run the borehole pump in warm weather).

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ProDave wrote on 28th July at 08:32pm

 It’s nice to see you making real progress. Frustratingly I’m still in the planning stages so can’t actually do much.

The DNO’s just seem to frustrate you, I have all that “fun” to come in due course.

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Jsharris wrote on 28th July 2013 at 09:57pm

 I’ll admit to being pretty excited now, as my confidence level at being able to pull this off grows! I’ve had the gnawing doubt that, as a beginner at this self-build lark, I’d made some seriously expensive errors somewhere. The major area of worry for me has been the ground works, particularly the setting out and accuracy of the topo survey and my site plan. Now we have the wall up (and in the right place) and the house base laid out, it all seems to be coming together.

The DNO saga is, according to Ben (my ground works chap) very typical. His view was that every project he works on gets buggered about by the utilities, with the DNO causing the most problems. The problem isn’t with the local engineers, they are all helpful and bend over backwards to overcome the shortcomings of their employer. If anything the local engineers are more frustrated with their own company than I am. The problem seems to be that the DNO just aren’t really geared up to handle single new build requirements. Not only are they very expensive (my £3500 has paid for 30m of cable, two cable joints and one new pole, with me paying for all excavation, ducting, backfill and making good), but they are incredibly slow and inflexible. An example is their inability to issue an MPAN number until the work is completed, so making it impossible for you to book the meter supplier early, and adding their lead time on to the total time it takes to get power on site.

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ProDave wrote on 28th July 2013 at 10:25pm

 I wonder what has changed?

When I built this house 10 years ago, we just filled in a simple form requesting a supply. Paid the fee and they came. The meter was fitted the same day by the same people.

Fast forward to now, and it’s a 5 or 6 page form to fill in.

Is your “problem” because you are choosing a different energy supplier to your DNO?

Something I never recommend.

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Jsharris wrote on 28th July 2013 at 10:41pm

The problem, at least in part, seems to be the split between the DNO and supplier forced by the government. In my case the DNO and the supplier are the same company, but are forbidden (by regulation) to talk to each other. I had the added problem that I needed a diversion of an existing cable, which is dealt with by a different department within the DNO (and yes, you’ve guessed it, the new connections team don’t ever talk to the network diversions team………..).

The net result is that I’m dealing with three parts of the same company, but who don’t talk to each other, either because of government regulations or because of company structure.

I had to fill in two forms, plus provide site plans etc back when I started this February/March, one for the diversion and one for the new connection. I had a site meeting with the local engineer when they put together the quote, and he said they’d roll the job into one combined diversion plus new connection. With hindsight I suspect this may be why the invoice for the new connection part was never sent out.

The system here seems to be that the meter supplier (same company as the DNO) cannot talk to the DNO part of the company, and operates completely independently. This means that they cannot programme a meter installation until the DNO part of their company has issued an MPAN number, and they only issue this when they’ve made the new connection (installed the head). Believe it or not, after the meter part of the company has been out to install the meter, I have to call the DNO part to tell them it’s been installed and get them back out to re-seal the company fuse, as the fuse and head belongs to the DNO part of the company and the meter supply part of the same company aren’t, apparently, authorised to replace the seal.

You really couldn’t make this up, could you?

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Notnickclegg wrote on 29th July at 09:26am

 The wheels of progress turn slowly, but turn they do…

My wife and I were talking last night about how stressful the build process was likely to be. So far, we’ve had a topo survey, a tree survey, engaged an architect and had an initial rough design put together, and have organised to have three trees taken down. I simply can’t believe the amount of hassle and stress involved in these pretty minor parts of the process.

As I’ve said before, Jeremy, I continue to watch your progress with serious interest. I only hope we make half as decent as fist of it as you’re doing.

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Jsharris wrote on 30th July 2013 at 11:05am

 The stress thing is quite interesting. The big stuff (retaining wall, designing the house, selecting a build contractor etc) hasn’t been that big an issue. The smaller stuff is what seems to soak up the time and cause frustration.

Having said that, I’m getting more convinced that someone from the DNO is reading this. At 08:00 this morning I got a call from the DNO giving me the much-needed MPAN number. I then called the supplier side of the same company, found they already had the MPAN and details on their system and can proceed a couple of days after the supply head goes live.

After months of becoming more and more convinced that this company was a bit of an organisational shambles, albeit with some good people working away at the coal face to patch things up, it suddenly seems to be working like a well-oiled machine. Why does this make me suspicious?

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Part Eight – The Wall

This eighth entry was published originally  on the 20th July 2013 and received 1,138 views on the old forum

Time for another update. In the middle of the biggest heatwave we’ve seen for years, we’re pressing on with the build of the concrete retaining wall. It’s a bit tedious, and none too green, as the compromise we’ve had to adopt is for a vertical, steel reinforced, concrete block wall. It’s overkill in terms of the ground it’s actually got to hold back, as that seems to stay up even with a vertical sided 2.5m face, but it does reassure the neighbour that the end of his garden won’t collapse into our hole.

Last weekend we left the site with the concrete wall foundation having been poured and a mass of 12mm rebar sticking up vertically at the base of the cliff. Our neighbour to the north is an elderly gentleman who’s fond of the shrubs in his garden, some of which are close to the edge of the cliff we’ve dug out. I woke up in the early hours earlier this week having had a dream that he’d been attending to his shrubs and fallen over the edge, impaling himself on the rebar spikes, rather like a punji pit. This photo was taken yesterday, after the lower few courses of blocks were laid, but there are still spikes sticking up in the air, ready to catch unwary prey that falls over the edge:

The punji trap

Much of the week has been taken up with building this wall, with a few other smaller jobs having been done, like filling in the service trenches and pulling cables through ducts. On Tuesday I went out to double check that the soil pipe was coming up in the right place, and lay out where the water, phone and electricity supply ducts needed to come up inside the house. These are fairly critical, as they have to be aligned so that they pop up just inside the inner face of the wall of the house, and, because of the foundation system we’re using (more on this below) we don’t have the luxury of having footings trenches to guide us as to where things need to go. Because the soil pipe went in when the treatment plant was installed, right at the start of work, the position of the soil pipe was worked out by measuring out from the reference peg in the north east corner of the plot (now excavated away) and running out along a horizontal radial distance and dropping down to the excavated ground level with a vertical pole. We’d anticipated having to shift this pipe around a bit to finalise the position, so were a bit amazed to find that it was within 15mm of where it was supposed to be.

To save having to pay two lots of charges for an electricity supply, one for a temporary contractors supply and another for the permanent metered connection, I came up with the cunning plan of fitting the meter box in a timber fence, that will eventually form the screen for the mandatory recycling/refuse bin area. This is easily accessible for the meter reader, yet means we don’t have the house defaced with a surface mount meter box carbuncle (we couldn’t have an inset flush mount meter box as it would severely compromise the insulation). This means we will just have the meter installed early and use the supply as a contractors supply for the build, and then just hook it up to the house when we’re ready. This short fence (which is planked on both sides) also houses the telephone junction box for the incoming line and a water standpipe from the borehole. The net result is that at it’s base we have a Medusa’s head of bits of ducting poking up at the moment. Hopefully we’ll find a way to hide this lot somehow, maybe with a small rockery.

The main visible change on site this week has been The Wall. It’s been pretty hot work for the guys, and not much fun heaving around big high density concrete blocks. Still, we have around a third of the wall up, after about three days of wall construction, which isn’t bad going. The wall is two (225mm wide) blocks thick at the base, but only a single 225mm block thick for the upper half, so thing should go quicker as it gets higher. It can only go up around four or five courses before they have to stop and pour concrete into the holes in the blocks, creating solid reinforced concrete internal vertical beams to hold the wall together. Everyone who’s looked at it thinks it’s a massive overkill, but best to be safe. At least I won’t be waking up in the early hours having had nasty dreams of the whole lot collapsing on the back of our house………….

The wall will be topped with a 700mm high reconstituted stone wall on the neighbours side and a layer of 100mm blocks on our side (which will be rendered, like the rest of the wall). That will then have a low a timber fence, infilled with trellis panels, built on top. Much of this wall is over 2m high to the existing ground level above, so when topped with another 700mm we’re going to have around 2.5m plus of rendered wall running along much of the north boundary. As the guys have been finding out, we have created something of a sun trap here. We’re already thinking about what we might be able to grow up this wall – my guess is that we could grow some pretty exotic fruit trees (as espaliers) or perhaps climbers, up it. It’ll be completely sheltered from the east wind by the house and fairly well sheltered from the west by the garage, so should be OK for sun loving plants.

The Wall

 The foundation system is a bit unusual, in that it sits at the level the ground is at the moment. There will be a 150mm deep hole dug out, a bit bigger all around than the house footprint, and this will be filled with compacted crushed stone. On top of this will be laid a 300mm thick polystyrene insulation layer, that includes a preformed ring beam former around the edge. The damp proof membrane will then be laid into the big polystyrene tray, steel reinforcement and the under floor heating pipes will be laid, and then it’ll be filled with concrete. The whole weight of the house will be supported entirely by the thick layer of polystyrene foam, which will form a very high performance insulated slab. The load is distributed into the ground by the compacted crushed stone base. This system works even on poor soil, as the bearing pressure it exerts is very low, especially with a timber frame house like ours. The walls will be constructed directly off the reinforced concrete ring beam that sits on top of the foam, which is stiff enough to make sure that everything stays square and true. Because the insulation is wrapped up around the edge of the slab, there’s no problem with cold bridging at the floor/wall junction, as there is with many conventional insulated floor systems. In effect, we will have a continuous layer of insulation running all around, over and under the house.

The system we’re using is the one that our builder, MBC Timberframe Ltd, include in their package build and is the Kore Passive Slab. There are other similar systems around, but they don’t seem to be in common use yet.

Part Seven – Pouring Concrete!

This seventh entry was published originally  on the 12th July 2013 and received 1,198 views on the old forum

Wonder of wonders, the DNO turned up mob-handed yesterday and moved the cables and made all the new connections, leaving us with a site with no obstructive power cables. Only taken 2 1/2 months – maybe they are reading this blog?

Today was a BIG DAY, but not, I have to say (with some regrets) a very green day. To cut a long story short, having settled on using gabions and timber crib for the big retaining wall we ran into a small problem with our neighbour. The said neighbour has been fantastically helpful, but was clearly unhappy about his garden being retained by gabions and timber crib (and the end of his garden is around 2.5m above our plot). He also wanted the boundary fence replaced as a stone wall, which makes a lot of sense given the big drop the other side, and it would have been hard to sort out foundations for this on top of the gabions and crib.

After much deliberation we opted to go back to a reinforced concrete block wall, which does have the advantage of giving us a bit more garden space, but more importantly allows the boundary wall to be built directly on top. The downside is the slightly higher cost (maybe £5k more than the gabions/timber crib) and the use of more than 100 tonnes of concrete in the reinforced concrete foundations alone.

This brings me to the reason today was a BIG DAY. Somehow, pouring the first load of concrete marked a turning point from just clearing the site and removing stuff, to actually starting to build something. Yet again I’m as chuffed as ninepence with the ground works guys. The temperature on site this afternoon was up in the mid-thirties (it faces more or less south, and is in the bottom of a deep valley), yet the guys worked their socks off as lorryload after lorryload of concrete turned up. The fact that the concrete supplier was two hours late, then sent lorries in very quick succession, added to the pressure.

Here are the latest crop of photos:

First, the plot minus the overhead cables:

No cables

It looks better already, just need to get BT to move their single cable and then get the DNO back to take down the redundant pole. They won’t let me keep it, unfortunately – pity as I had an idea to use it as a raised bed surround.

The concrete arrives

Much excitement (for me at least) when the first load of concrete turned up. Better late than never……….

The first pour

Finally, the momentous moment when the first bit of real construction starts.

Part Six – There We Were, Digging This Hole…………

This sixth entry was published originally on the 10th July 2013 and received 1,360 views on the old forum

I know I’ve missed bits out, but frankly that’s because the plan for this blog seems to have gone for a ball of chalk. Luckily the plan for the build is on schedule, despite the best attempts of a well known utility company to hold us up.

A few hundred cubic metres have now been dug out, leaving us with this partially excavated hole:

The hole - N face

The ground works chaps (that’s Scottie in the photo, BTW) are currently putting the steel in for the retaining wall founds, with luck they should do the pour on Friday. Here’s another view of the North face of the excavation that gives a better idea of the scale of the retaining wall (this time with boss man Ben walking away from the camera):

The north face

I’m dead impressed with the ground works guys, not only have they had to deal with being dicked around by the utility companies (who are seemingly unable to get their act together, despite charging vast amounts of money and being given months of notice), but they’ve also cracked on and done more than I expected at this stage, and, most importantly for us, they’ve done a really good job of keeping the site clean and tidy and keeping the neighbours happy. If anyone in the Salisbury/Andover general area is looking for a good ground works firm, then I’d recommend these guys.

Once the retaining wall is up, probably by around the end of next week with luck, I think we’ll all relax a bit, as that steep cliff at the back of the plot isn’t going to stay like that for ever on its own. I’ve got the borehole rig arriving on site in around three weeks and had a site meeting with the driller last week, As we hit the water table when digging the trenches for the utilities we at least know we have water. In fact, as SWMBO wants a water feature in the garden all I need to do is dig a hole about a metre deep and use it as a well, perhaps with a small solar powered pump, and we can have a water feature and irrigation system if we want, without needing to use the clean water from the borehole.

One ongoing issue is that we’ve had to work around problems caused by the tardiness of the DNO, as they have a big cable running across the plot that they still haven’t sorted. We stuck the new pole in for them (as they couldn’t get a digger to the site), we’ve dug all the trenches and laid new cables for them, all they need to do is get a jointing team in to disconnect the overhead wires and connect up the new underground cables we’ve laid. For that they’ve charged me over £3500, which I had to pay in advance back in April (yes, that’s right, I paid them to do this work just over 2 1/2 months ago!!!). I’m going to be arguing for a refund of part of this money, as we’ve done half the job for them. Luckily I had a brainwave (one that will probably cause the DNO to freak when they see it) and suggested that we just pull the problematic underground cable that was in the way (the one in the last photo of the previous instalment) away from the pole it runs down, to give a couple of metres of extra slack. This has been enough to be able to pull the cable to the side of the plot, allowing the excavation for the retaining wall to be completed. Had this not worked we’d have been twiddling our thumbs, waiting for the DNO to get their act together.

By way of contrast, BT Openreach (who also have overhead cables we need to shift) have been very helpful at the local engineer level. The downside is that, as an organisation, they really couldn’t organise a piss up in a brewery. An example: The helpful local engineer arranges to drop off a load of free issue duct 56, some hockey stick bends to run up the new poles, a roll of 28 pair cable and a couple of cast iron ground mounted termination boxes for the ends of the ducting. Believe it or not, these items arrived as FOUR separate deliveries, spread over ten days, from the same depot in Basingstoke, around 50 miles away. All told their delivery drivers clocked up around 400 miles delivering this stuff, when with a bit of coordination they could have done it in one run of 50 miles each way. Still, I can’t complain, as they are doing the underground diversion for us free gratis.

I’ve no doubt there will be photos of concrete being poured in the next instalment, but for now this is what the plot looks like (Scottie and Joe on the right aren’t worshipping boss man Ben on the left, they’re manhandling a sheet of steel mesh!):

The plot revealed - 2

 Here are the calcs and drawings for that wall:

Retaining wall drawings

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joiner wrote on 20th July 2013 at 01:44 pm

 

Excellent stuff!

Part Five – Trials And Tribulations………

This fifth entry was published originally on the 26th June 2013 and received 1,149 views on the old forum

Well, it’s been a fair time since the last entry, and much has been going on. I’ll gloss over the financial issues, suffice to say that the moral of the tale is to never, ever, trust a bank to tell the truth, and most of all, never, ever, believe any promises made by Santander. I could expound on this at length, but suffice to say they made us a firm mortgage offer on our existing house (for a fraction of its value) then withdrew the offer at the very last minute (literally on the day I went to draw down the mortgage).

Leaving aside the finances (which we have finally sort of resolved) we next ran into delays caused by, yes, you guessed it, services…….. We need to move some electricity cables, both overhead cables and a big fat underground cable. I first arranged all the details for doing this back in the early spring. I paid the electricity company £3500 in advance 6 weeks ago. I had been told that they needed at least three or four weeks notice. Guess what, after 6 weeks they tell me that they can’t do the work for another 5 weeks. I refrained from losing it with the guy at the company, as one thing I’ve learned is that venting your spleen at people like this, no matter how stress-relieving it may be at a personal level, rarely results in moving things on. To the chaps credit, he did then offer to come out to site and is trying to work through a compromise, albeit one that means I have to dig holes for his pole etc, even though I’ve already paid them to do this.

Still, on the bright side, we eventually got diggers on site at the start of the week, and started work. Great fun, as we’ve not been able to walk on and see the site since we bought it back in November, as it’s been too overgrown. This gives an idea of how it looked on Monday:
The diggers arrive

After a couple of days work we have cleared all the overgrown shrubs etc and got to this:

Looking across the plot from the top of what will be the retaining wall - Copy

There are still a few hundred cubic metres of soil to come out yet, as where I’m standing to take this photo will be around 2.5m lower when everything is at the finished levels. To the lower left you can see the errant power cable that runs diagonally under where we want to put the house. We need to shift this (and the pole it runs to) to the left corner (as viewed from this picture). One slight problem is that this is going to cause some inconvenience to the neighbours, as that big cable supplies power to quite a few houses in the village. On the positive side, it does mean we have three phase power right next to where our meter box is going, which bodes well for connecting up a big PV array.

I’ve given up predicting what the next episode of this blog will be. Predicting how a self build will go, even after as much planning as we’ve done over the past 18 months, seems akin to trying to forecast the weather a month in advance. Stayed tuned, folks, as I’m sure there are more fun and games to come.

 

 

 

 

 

 

 

 

 

Part Four – Services

This fourth entry was published originally by JSHarris on the 9th April 2013 and received 1,301 views on the old forum

When we bought the plot we knew that getting services in was going to be a costly business. The nearest water main was over 140m away and the nearest sewer was around 85m away, both up a steep, single track lane. Luckily the electricity supply and telephone were at the edge of the plot, but both had cables that were in the way, plus we had a pole that would be right in front of the house if we left it where it was.

I first got the water company to quote for a connection to the mains water supply and sewer. Unsurprisingly, they wanted around £30k to connect to both services (£22k of that was for the water connection), but there was a fairly large (~£26k) contestable element, so I could look at getting this part done by another approved contractor. After some ringing around I had a best estimate of around £16k, plus the £1k highways fee, for the contestable work, giving a total of around £21k. A fair bit cheaper than just going with the water company quote, but still a lot of money. I’d also need a sewage pumping station, at an additional £1.5k or so, bringing the total to around £23k, just for water and sewage.

With costs this high I needed to look at other options, so I looked at getting a private borehole for water and using a package treatment plant for sewage. The latter was the main problem, as a previous planning application for this plot had suggested using a package treatment plant and the Environment Agency had refused to allow it. There is a stream running close to one boundary and the EA had taken the view that the plot should be connected to the main sewer, as there was supposed to be one in the area.

I decided that, given the high cost of connecting to the main sewer, it was worth approaching the EA again, as there was a clause in the building regulations that allowed a package treatment plant if the distance to the main sewer was more than 30m. I was pleasantly surprised to find that the EA were quite helpful (although slow, as they don’t use email or ‘phones!). They granted me permission to use a package treatment plant and to discharge the effluent into the stream. As the cost of a treatment plant was broadly similar to that of a pumping station, this decision represented a significant overall saving.

Water was much easier, as no permission or licence is required for a domestic borehole, provided you don’t draw more than 20,000 litres of water from it each day. As we would be unlikely to use more than around 300 litres per day we could just drill a hole and have our own virtually free water supply. I already knew that the area had abundant water in a fairly shallow underground aquifer, as there are springs all around, and several other boreholes nearby. Nevertheless, I decided to get a full hydrogeological survey done (fairly cheap, at £300, and well worth the money).

I went out to tender for the borehole and was amazed at the variation in quotes received. Given that I’d sent copies of the hydrogeological report to each of the bidders, with a detailed specification for the borehole, I expected the quotes to be fairly close. The four quotes I received ranged from just over £9k to over £20k, with a fairly even spread between these figures. Just goes to show that it’s well worth shopping around. The end result of all this work was that I’d got the total cost of the water and sewage services down from around £23k to just over £11k, plus we will save the ongoing cost of paying for water and sewage disposal.

The package treatment plant we’ve opted for (a small Bio Pure 1E) will need de-sludging about every three to four years (at a cost of around £200 to £300) and it only uses about 30W of power (so an additional £40 in electricity each year, less whatever we generate from PV). The borehole pump will use around another £20 of electricity a year, plus £30 to £50 a year for UV treatment (if we need it, and again less whatever we generate from PV). Our total annual costs for water and sewage should be around £180 to £200 at the most, significantly less than our current water and sewage charges of around £600 a year.

Next I had to sort out the electricity supply and telephone. Both of these gave us problems, as there was a combined electricity/telephone pole obstructing part of the new drive, plus there were overhead cables that crossed the plot and severely restricted the use of cranes etc. The local DNO*** were very helpful, responding to my request within a couple of days, making a site visit and quickly giving me a quote to move the pole and relocate all their cables underground (with me digging the trenches and laying ducts). It was quite reasonable, too, at £3.5k, especially given the length of new cable they had to put in. The telephone network provider, Openreach, was a different kettle of fish, though. In fact they were nothing short of a complete and utter shambles. I contacted them in early January, by mid- March they still hadn’t got back to me. Eventually, after a couple of hours effort, I tracked down a telephone number (they don’t make their ‘phone numbers public, in case anyone might want to ring them…….) and managed to get hold of the mobile number for the local chap who looks after things. He was very helpful (in complete contrast to his own management), came out straightaway to look at things, agreed with our proposal to move the cables and quickly came up with the best way to get their work and that of the DNO synchronised.

In essence, we dig the trenches and lay the ducts, the DNO erect a new pole and move all the power cables (leaving the ‘phone cables on their old pole), plus hook up our new supply to a meter box that I’m having fitted into a low fence at the side of the plot. Openreach then come out and move their cables into the ducts and across to the new pole and then someone (the DNO?) takes down the old pole. This all sounds too sensible to actually work in practice. We shall see in a few weeks time.

***DNO – Distribution Network Operator, the people who look after the local power grid. In our case this is Scottish and Southern Electricity.

Next – the minefield of choosing contractors

PS: If anyone wants the spreadsheet I mentioned in the last episode, the one that I used to help check that the retaining wall is safe, then PM me. It comes with no warranty, and needs a basic understanding of the data needed, but I’m happy to let it out in the wild if it might help someone.

 

Part Three – The Devil Is In The Detail (Episode One)

This third entry was published originally  on the 8th April 2013 and received 2,149 views on the old forum

Having received planning approval, the next step was to get the pre-commencement planning conditions discharged. We had four of these, one needing details of surface water management to be approved, one asking for details of a scheme to keep mud off the road during construction, one that required external materials to be approved prior to commencement and one for approval of a landscaping plan before we start.

I addressed the surface water run off and landscaping condition together. Having looked at the cost of getting a professional landscape design (upwards of £800) I opted to do it myself. I kept the detail to a minimum, on the basis that being overly specific might well cause problems later if we changed our minds about plant species etc. I did detail how surface water from the house and garage roof would be fed to soakaways, and that the drive would be surfaced with permeable, SuDS*** compliant, pavers. A fairly simple site plan, showing the layout of the drive, soakaways etc, together with some details of key planting, was drawn and accompanied with a photo of the scale model to illustrate how the landscaping might look.

Dealing with the “mud on the road” was just a matter of providing an assurance that contractor’s vehicles would be inspected before leaving the site and their tyres/tracks cleaned if necessary.

The final condition was to get approval of the roof and external cladding material. I’d included photos of these in the Design and Access Statement, so assumed that the planning officer would now need to see samples, rather than just photos. I duly drove around the country gathering bits of wood, roofing etc, and then called the planning officer to ask when and where he’d like to inspect them. This resulted in an interesting Catch 22 moment. I was told that, because of health and safety issues, I would not be allowed to bring the samples to the council offices. Instead the planning office suggested a site visit. I pointed out that the site was overgrown with 4ft high brambles and surrounded with security fencing, and that I couldn’t lawfully start work on it to make it accessible until I had the pre-commencement conditions cleared, one of which was the approval of external materials. The planning officer then suggested that I take photos of the materials and that he would accept them instead. I then pointed out that I had already done this, and that they were in the D&A Statement that formed part of our application. The response was for me to just reference the D&A Statement in the application for discharge of conditions. I had to wonder why the approval of materials had been added as a pre-commencement planning condition, particularly as obtaining approval turned out to be just reminding the planners of what I’d put in the original application.

The up side of this was that I submitted my form (and fee) for discharge of these conditions on the Monday afternoon and received a letter telling me they had been discharged the following Thursday morning. Quite a remarkably quick turnaround, and far faster than I’d assumed.

Having finally got the paper work out of the way, I could make a start on getting some of the details sorted out. We knew that services would be a problem (more on that in the next episode) but the first priority was getting the design of the big retaining wall we needed right. I knew this was going to be costly and potentially problematic, as it is around 2.5m high in one corner and around 40m long in total. To add to the potential difficulty, the wall needed to be as thin as possible, particularly in the north east corner, in order to get the house as far back in the plot as possible, leaving room for the drive at the front. Having looked at various options, I first settled on this being a plain hollow block reinforced concrete wall, rendered to make it look reasonable. I duly went to a couple of structural engineering firms and asked for quotes to design the wall, explaining the constraints. The first came back with a quote for £1500 (inc VAT) just to do the design work, which seemed massively OTT. The second was a fair bit better, at £360 (inc VAT), so we went with them. This turned out to not be a great idea, as when I got quotes for constructing the wall they came in at £25k to £32k, far more than I’d expected. There was also a problem pointed out by one of the ground works companies, in that the width of the wall footings was such that the house wouldn’t fit where it was supposed to be.

Having wasted the money on the SE’s design, I decided that I’d look at all available options and design the wall myself, doing my own structural calcs. With hindsight I should have had the confidence to do this at the start. I looked at several different systems, from the big, dry laid, block systems, like Porcupine, Redi-Rock, Allan Block etc, through dry laid, but reinforced concrete filled systems, like Stepoc, to gabions and timber crib.

The cheapest were gabions, but when I’d originally looked at using them, the advice I’d had was that they would take up too much space, plus they don’t look that great, IMHO. Timber crib is somewhat more expensive than gabions, but takes up as much, or even more, space, but does look more attractive.

Although I’ve done a fair bit of structural engineering work in the past, it has all been associated with aircraft structures, not civil engineering. A quick crash refresher course on retaining structures, Rankine etc revealed that the engineering design for retaining walls is pretty straightforward, so I cobbled together a spreadsheet to allow the calculations to be done quickly and repeatedly. The idea was that I could try lots of different designs by just sticking some numbers into a spreadsheet and seeing if they stacked up.

The first discovery was that vertical gravity walls, using gabions or blocks, are a bit of a disaster structurally. For them to be structurally sound at anything over about a metre high they need to be ridiculously deep (front to back). My 2.5m high wall would need to be 2m deep at the base if I used vertically stacked gabions, just to get an acceptable safety factor against overturning. This was no better than the reinforced concrete block wall.

However, by creating a batter angle (effectively leaning the wall back a few degrees), the resistance to overturning increases massively, and the overturning moment from the backfill and soil behind actually decreases, allowing the wall to be made a fair bit thinner. In practice this batter angle can be achieved without actually building on a slope, by just stepping back rows of gabions to form a shallow terrace. The depth of the gabions at the top can also be reduced, so reducing the overall footprint of the wall.

After several iterations of different gabion designs I ended up with something that would fit in the available space, be significantly cheaper and be OK for the less visible wall section behind the house. We didn’t want gabions for the more visible wall section behind the garden, though, so opted to use timber crib (the Permacrib system from Phi). The same basic design spreadsheet worked OK for this wall system, so after a few hours work I ended up saving money and getting a reasonable compromise design for this wall.

I also learned during this design process that gabion wall design can be very sensitive to things like rock fill density and backfill material choices. For example, my ground works chap suggested that backfill with shingle, rather than crushed concrete, would be much quicker, as it wouldn’t need to be compacted in layers. A quick check with the spreadsheet revealed that doing this would result in an increased risk of the wall falling over, just because the internal friction angle for pea shingle was so much lower as to put excessive horizontal force on the rear of the wall.

***SuDS – Sustainable Urban Drainage System, see: http://www.susdrain.org/