Can a slab be too thick to have UFH pipes in it?

[Thorfun]

2 hours ago, Rob99 said:

No luck on the UFH pipe I'm afraid ☹️   

Looked everywhere I can think of but don't seem to have kept any (very unusual for me!!) possibly as I only had small offcuts and couldn't see any use for them. 

Found loads of spare bits of the JG 15mm pipe but that's no help.

 

no problem and thanks for looking. I will bite the bullet and order some 16mm elbows.

[dpmiller]

JG and Polyplumb UFH are both 15mm which might explain any confusion.

 

These guys have a good range of 16mm fittings and adaptors:

https://pswtradesuppliers.co.uk/

[Thorfun]

so, after all of that I decided to just buy the manifold and fit it now! when I started to add it all up it was almost half the price of a manifold. 

 

thanks for everyone's advice and I think this was a good example of not seeing the woods for the trees as I got so blinkered about using elbows that I didn't see the benefits of just skipping to the end result. it's amazing how focused you can get and it takes a moment or two of stepping back from the problem to see and consider all the other options.

[Rob99]

Sounds sensible @Thorfun

When you connect up the loops you can fill each one individually by closing off all the other valves except that loop.

I found this much easier to make sure all the air was out of each loop and to pressure test each one seperately.

Have fun.

 

[Nickfromwales]

Make yourself a box out of OSB / PLY, fill the inside with bubble wrap, and slide that over the manifold to keep it in one piece.

[Thorfun]

8 minutes ago, Rob99 said:

Sounds sensible @Thorfun

When you connect up the loops you can fill each one individually by closing off all the other valves except that loop.

I found this much easier to make sure all the air was out of each loop and to pressure test each one seperately.

Have fun.

 

that's how Wunda suggest to do it.

 

https://cdn.wundatrade.co.uk/wp-content/uploads/2017/08/M07-generic-Wunda-premium-Manifold-2-5-2017.pdf

[Thorfun]

6 minutes ago, Nickfromwales said:

Make yourself a box out of OSB / PLY, fill the inside with bubble wrap, and slide that over the manifold to keep it in one piece.

is that to protect it during the liquid screed pour? or for some other reason?

[Adrian Walker]

On 01/05/2021 at 18:55, Thorfun said:

5 x 3m 3wire 1-wire temp probes ordered from eBay and delivered ready for installation!

 

thanks. I've told Wunda I only want the pipe for now and they were ok with that.

thanks Rob but I've already ordered it. I could probably cancel it but it's done now and I'm on to the next thing to organise. 

If you are buying DS18B20 sensors make sure they are the real thing, not copies and work properly.  They all have a unique serial number. Someone on here bought a load and calibrated them, I think 3 out of 20 failed.  

[Nickfromwales]

1 minute ago, Thorfun said:

is that to protect it during the liquid screed pour? or for some other reason?

To protect it against EVERYTHING lol. Including the unknown.

[Ajn]

39 minutes ago, Adrian Walker said:

If you are buying DS18B20 sensors make sure they are the real thing, not copies and work properly.  They all have a unique serial number. Someone on here bought a load and calibrated them, I think 3 out of 20 failed.  

would agree with that, I got 15, so far used 6 (7) one was faulty. Also had to add a calibration factor to all of them. All were reading high, max was 2 deg, min was 0.5 degrees. Used a medical thermometer as the ref.

[Ajn]

44 minutes ago, Ajn said:

Used a medical thermometer as the ref.

used the armpit before anyone questions it... not where the sun does not shine.

[Rossymcg]

On 21/04/2021 at 15:54, Thorfun said:

I know a large number of folks on here have insulated slabs where generally the slab is 100mm thick and the UFH pipes are cable tied to the rebar. 

 

We're going this route now for our basement UFH but our slab is 250mm thick with 200mm EPS underneath.

 

I was just wondering if a slab ever got to a thickness where putting the pipe within the slab became the wrong thing to do?

 

I'm building a house in Poland, it will be insulated and airtight to passive standards. The design is for 200mm EPS and 250mm of concrete(it's a raft foundation) how did the 250mm of concrete heat up in the end

[Thorfun]

2 hours ago, Rossymcg said:

 

I'm building a house in Poland, it will be insulated and airtight to passive standards. The design is for 200mm EPS and 250mm of concrete(it's a raft foundation) how did the 250mm of concrete heat up in the end

I didn’t put the ufh pipes in the slab in the end. They’re in a 60mm Cemfloor screed on 25mm PIR on top of the slab. 

[Rossymcg]

2 hours ago, Thorfun said:

I didn’t put the ufh pipes in the slab in the end. They’re in a 60mm Cemfloor screed on 25mm PIR on top of the slab. 

OK never mind. you happy with that?

[jack]

5 hours ago, Rossymcg said:

I'm building a house in Poland, it will be insulated and airtight to passive standards. The design is for 200mm EPS and 250mm of concrete(it's a raft foundation) how did the 250mm of concrete heat up in the end

 

Welcome to BuildHub.

 

There are definitely at least a few BuildHub members who used 200+ mm concrete slabs in a raft construction.

 

More common is a nominally 100 mm reinforced slab on a raft with 200-300 mm of EPS underneath. However, by the time you factor in a 300mm deep ringbeam, 200 mm deeper reinforcement ribs and 200 mm deep reinforcement areas for structural walls, the average thickness is actually much higher than the nominal 100 mm would suggest. Overall, the performance of a flat 200 mm slab probably isn't that far off a 100 mm slab with all the extra deep bits.

 

Try these two Google searches for more info:

https://www.google.com/search?hl=en&q=250mm slab raft site%3Abuildhub.org.uk

https://www.google.com/search?hl=en&q=200mm slab raft site%3Abuildhub.org.uk

 

[Thorfun]

2 hours ago, Rossymcg said:

OK never mind. you happy with that?

Yes. Works fine. But it is a basement so the temperature doesn’t really fluctuate and we rarely have the heating on down there. 

[Rossymcg]

On 09/12/2024 at 10:59, jack said:

 

Welcome to BuildHub.

 

There are definitely at least a few BuildHub members who used 200+ mm concrete slabs in a raft construction.

 

More common is a nominally 100 mm reinforced slab on a raft with 200-300 mm of EPS underneath. However, by the time you factor in a 300mm deep ringbeam, 200 mm deeper reinforcement ribs and 200 mm deep reinforcement areas for structural walls, the average thickness is actually much higher than the nominal 100 mm would suggest. Overall, the performance of a flat 200 mm slab probably isn't that far off a 100 mm slab with all the extra deep bits.

 

Try these two Google searches for more info:

https://www.google.com/search?hl=en&q=250mm slab raft site%3Abuildhub.org.uk

https://www.google.com/search?hl=en&q=200mm slab raft site%3Abuildhub.org.uk

 

thanks for that. 

 

[Gus Potter]

Bit of general comment from me re slab thickness and UFH, pipe abrasion / expansion, concrete slab shrinkage and stuff. Excuse the spelling and grammer please as I'm off duty.

 

I'll start with my plumbing / concrete hat on, also bringing to the table that I've been "experimenting / sefl building" with different UFH designs for the last 30 years.

 

Ok if you have structural slab you probably want to put the crown of ( the top of the pipe) UF pipe say 40-50 mm below the surface. This allows for a sensible construction tolerance and the unexpected pipe overlap when you make design changes at the last minute. There are some that advocate for less but this is self building.. cut yourself and the builder some slack.

 

**This is self building.. you generally don't have the same control over workmanship as say on a major contractor project.. keep things simple stupid. If you are anal and want to tie down your builder to tight tolerances then you either need to be able to check this or you will end up paying for something that never gets delivered. I see this all the time!

 

Now if we have a simple ground bearing slab on say EPS then I would put the anticrack rebar mesh near the top of the slab. I have on several occasions tied the UFH pipe to the mesh.. with zip ties. Now this can be great thing to do yourself. It gives you that feeling.. here we are putting in the pipes that are going to make our home warm.. it's romantice and gives you a spurt of joy / keeps the spiits up. I say this as I've done this and felt it more than once.

 

Get the builder to lay in the mesh and tie down your own UF pipes! A good way of getting it right.

 

Now lets look at the behavoir of the concrete and the UF pipe preparation. Most UF pipe is rated to 10 bar (it decreaes depending on temperature). I tend to pressurise the UF pipe to 4 bar and hold that for a couple of days.  Now I lay the concrete. The concrete has plastic shrinkage ( first 7/ 8 -24  hours / then drying shrinkage. My own experience tells me that the concrete shrinks a little (a mircon of two) away from the pipe and the rebar. Pretty much all heating sytems have a pressure relief valve set at 3 bar. In the round my view is that pipe abrasion can be shown by calculation to be negligeable / none at all.

 

BUT .. SE hat on now. If you have a concrete slab is a structural raft with big point loads then you can still put your UFH pipes in but I'll tell you where you can't put them. Generally it's not to onerous but you'll need to pay me a bit more to do you a couple of drawings.