IN a slab

[Big Neil]

I realise the answer is probably in the forum somewhere but I couldn't find it asked in quite the way i have the question in my head. IS the process of laying out (if not actually fixing) the pipe when putting directly into the slab, in principal any different to if you were pinning it to insulation/clip track, on the top of a slab? Are the materials Exactly the same, i.e. would one have to tell an UFH supplier whether the system was to be in concrete or screed?

[Jeremy Harris]

It's fundamentally different, as when putting UFH pipe in an insulated slab, the pipe only needs to be cable tied to the reinforcing fabric, so there is no need for clips, staples or whatever, just the pipe plus a big bag of cable ties.  Here's a photo of our pipes, about half way through being tied in to the fabric:

 

[recoveringbuilder]

Think I posted these before, company came out and did it in a day and a bit, they had pipe on a big roll and a machine that tied it to reinforcing mesh 

[Onoff]

Recommended to me by someone on here, Polypipe panels. They interlock and the pipe clips in:

 

Saves using the little standoffs and no cable ties. Also don't need a membrane between the concrete/screed and foil face of the pir.  

 

However...though I used them for one room I think I'd just cable tie to the mesh like the posters before above if doing the whole house.

 

Why? Well my bathroom slab is 100mm thick and because of the built in upstands you don't get the full 100mm depth so it sounds a bit "hollow".

[Big Neil]

1 hour ago, JSHarris said:

It's fundamentally different, as when putting UFH pipe in an insulated slab, the pipe only needs to be cable tied to the reinforcing fabric, so there is no need for clips, staples or whatever, just the pipe plus a big bag of cable ties.  Here's a photo of our pipes, about half way through being tied in to the fabric:

 

 

I may have seen that on your Blog @JSHarris, slowly reading around it at the moment. Is the actual pipe material any different? Could it just as easily have been stapled to the insulation and then have the rebar above it? If bought a system having had a company design the layout on the basis of if needing stapling to insulation and being under screed, but the after taking delivery decided I was going to put it in the slab. Would i effectively just have to bin the staples and buy myself some cable ties, both otherwise everything would be the same. Likewise would this go for BUteline, HeP20 etc etc

[PeterW]

Tends to be Pex-Al-Pex or Pert-Al-Pert for UFH pipe in 16mm these days as it’s cheaper than using the PB pipes and the Aluminum layer makes it more stable. 

 

What it is and where is reasonably irrelevant but being in the middle of the concrete slab is better than being at the bottom. 

[TerryE]

14 minutes ago, Big Neil said:

Is the actual pipe material any different?

 

Nope.  and no your don't want to put it under the rebar.  Our slab was build using exactly the same technique and there's a couple of similar pics on my blog.  The rebar is all cut placed and tied. It is lifted onto the concrete block stand-offs pretty much last of all.  If you zoom into the photo then you will see that they only bother with the minimal number of ties to keep the runs in position and straightish.  Remember that in terms of the vertical tolerances this approach roughly centres the pipe in a 100mm slab so it doesn't need the same tight anchoring as an in-screed installation.  The laying of the UFH is the last thing that they do before the pour.  Adding the UFH was only about £2K extra in out build.  An absolute bargain and a lot cheaper than in-screed versions.

Edited December 15, 2018 by TerryE

[Jeremy Harris]

9 minutes ago, Big Neil said:

 

I may have seen that on your Blog @JSHarris, slowly reading around it at the moment. Is the actual pipe material any different? Could it just as easily have been stapled to the insulation and then have the rebar above it? If bought a system having had a company design the layout on the basis of if needing stapling to insulation and being under screed, but the after taking delivery decided I was going to put it in the slab. Would i effectively just have to bin the staples and buy myself some cable ties, both otherwise everything would be the same. Likewise would this go for BUteline, HeP20 etc etc

 

The pipe is standard 16mm UFH pipe.  It needs to be above the insulation, plus the slab needs to have a minimum concrete cover over the fabric, so it's easier, cheaper, quicker and better to just fasten the UFH pipe directly to the fabric.  Ours was done by the foundation team, as an intrinsic part of laying the passive slab, and didn't involve a UFH company at all.  They left the pipes poking up out of the finished concrete, and when the house was up, I just connected the pipes up to an off-the-shelf manifold and pump set.

[Big Neil]

Lovely stuff - IS it held under pressure whilst the concrete is being poured to avid compressing the pipe? Were you at all worried about warranty being an issue with not getting the whole system from a single supplier? It has always seemed to me that warranty concerns aside, it really wouldn't be that hard to design a layout, once you know where the edges of the building are and where the internal walls will be.

[TerryE]

I see that Christine has her manifolds fitted before pour.  Like @JSHarris  they just cut off spare on the tails and tied them to a couple of bits of 2×4 which were tied to a couple of rebar verticals to hold them in the right position.  We just taped over the ends and left them dry to avoid the risk of freezing.  We only fitted the manifolds and pressure tested months later (about a year later, I think)  once the internal were thoroughly dry and insulated as part of second fit.

Edited December 15, 2018 by TerryE

[Onoff]

Don't hang about pouring the concrete once the pipes are tied on as you can tread on the mesh and abrade the pipes.

 

 

My pipes were under the mesh but same potential issue.

[Big Neil]

13 minutes ago, PeterW said:

Tends to be Pex-Al-Pex or Pert-Al-Pert

 

can't seem to find anything telling me the difference and relative benefits. Plenty of suppliers like wundatrade but no side by side comparisons that i can find. THat wundatrade has a 500m coil of pert al pert for 265 sheets. Is that good, bad. Is it too cheap?? All the sample costs i've ever seen are from designer suppliers lie continetnal, nu-heat etc

[Big Neil]

@Onoff. What made you choose to go under instead of over the mesh?

[PeterW]

23 minutes ago, Big Neil said:

Lovely stuff - IS it held under pressure whilst the concrete is being poured to avid compressing the pipe? Were you at all worried about warranty being an issue with not getting the whole system from a single supplier? It has always seemed to me that warranty concerns aside, it really wouldn't be that hard to design a layout, once you know where the edges of the building are and where the internal walls will be.

 

Warranty on pipe is irrelevant - it’s running  at 2 bar most and even if it does fail, the warranty is limited to the pipe so you’ll be the one digging up several tonnes of concrete. 

 

Its really hard to crush it unless you put a point load on it so as long as you are careful then it’s not going to get damaged. Pressurising it with water does help somewhat with stopping damage but it’s not much in it tbh. 

[TerryE]

Just now, Big Neil said:

@Onoff. What made you choose to go under instead of over the mesh? 

 

People sometimes make decisions that they wouldn't repeat with 20-20 hindsight  ??.  Our slab crew had done 100s of slabs the way that J, C and I showed without any issue.  Rebar is heavy and the rebar ties are sharp.  They finished tying down ours at about 4pm and the up-and-over concrete pourer was in action about 9am the following morning, if I recall correctly.   

[recoveringbuilder]

Mine were pressure tested before the pour which was a couple of days later but we are talking about in June time when it was warm and dry weather 

[Onoff]

21 minutes ago, Big Neil said:

@Onoff. What made you choose to go under instead of over the mesh?

 

It was deliberate in my case. Using the Polypipe panels the Pex-Al-Pex 16mm pipe just flies in as per the video. It keeps the pipe up a bit too. The A142 mesh just sat on top.

 

 

In my case though I left a square to cast my own, to falls, wet room corner. When it came to it though I felt the slab wouldn't be thick/strong enough 

 

So I hacked out the Poypipe bit by bit ruining the pir foil face.

 

 

Repaired it (tin foil) and put a membrane down:

 

 

Then cast a wet slab to falls:

 

 

[TerryE]

30 minutes ago, Onoff said:

It was deliberate in my case

 

For more details read and the 2,000 (bar 33 posts as of today)  

 

 

Clive, surely you were taking risks doing it this way and not putting support stand-offs to carry the rebar between the piping?  You've got no way to stand in the room centre without pinching the pipe by the rebar under your weight.  Even if you'd had temporary blocks and a standing board on top until you concreted, then you could have avoided this pinching.

 

Edited December 15, 2018 by TerryE

[Onoff]

29 minutes ago, TerryE said:

Clive, surely you were taking risks doing it this way and not putting support stand-offs to carry the rebar between the piping?  You've got no way to stand in the room centre without pinching the pipe by the rebar under your weight.  Even if you'd had temporary blocks and a standing board on top until you concreted, then you could have avoided this pinching.

 

With hindsight etc! Tbh the pipe sits under the top of the trays but here and there as I trod on the mesh it did start to abrade the pipe without me realising it 

 

 

Edited December 15, 2018 by Onoff

[TerryE]

@OnOff, this hindsight stuff is brilliant isn't it?  It's a pity that the don't issue a Tardis as standard