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.

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