Building up floor level for UFH

[pilgrim]

Can anyone offer me some advice on the best way to build up my floor level for UFH installation?

I have removed the old suspended timber floor on the ground floor level as it was rotten, I now have a void of 330mm to fill to make up the floor level.

The house has a concrete base level which runs all the way through already.

I had planned to use some hardcore then soft sand, Damp proof membrane then insulation and UFH screed. but the building inspector did not like this plan and said he wanted me to pour more concrete in before adding insulation.

So now I am thinking off levelling off the existing concrete damp proof course, then adding 260mm of insulation, then finish off with 70mm of screed and UFH pipes.

Does this make sense? or can anyone suggest a better method?

Thanks

[Temp]

16 minutes ago, pilgrim said:

So now I am thinking off levelling off the existing concrete damp proof course, then adding 260mm of insulation, then finish off with 70mm of screed and UFH pipes.

 

That's probably the best solution. Put a 25-50mm sand blind below the DPM.

 

Perimeter insulation around the edge before screed.

[JohnMo]

200mm of PIR would give you a u value of 0.1 or less.

 

If you are using PIR, you can staple UFH piping directly to it.  But if using a concrete screed, you need to include a thin plastic DPM above the aluminium on the PIR insulation, to stop a chemical reaction.

 

Finish what ever depth above insulation with a screed of you choice.

[Radian]

Are you considering EPS for the insulation? 260mm EPS would still give you a U-value of under 0.15 and come in at a lower cost than PIR. Usually PIR is chosen for it's space saving properties but you've got the space!

[Temp]

A mixture is also a possibility. I'd put EPS on the bottom.

[pilgrim]

1 minute ago, Temp said:

A mixture is also a possibility. I'd put EPS on the bottom.

Yes this is what I had thought, EPS to build up the bulk then PIR on top of that and then the UFH pipes. I had also been looking at the egg crate style boards to lay it on, one of my friends recommended that for ease of fitting over the staples. Ive not fitted any UFH before so open to other opinions!

[JohnMo]

You can't staple to EPS, hence EPS at the bottom.  If you are splitting use 50mm PIR minimum.  Otherwise your staples will pull out.

[pilgrim]

12 minutes ago, JohnMo said:

You can't staple to EPS, hence EPS at the bottom.  If you are splitting use 50mm PIR minimum.  Otherwise your staples will pull out.

Ah ok, thanks for the heads up!

[Conor]

Stapling ufh pipes into PIR is easy. We laid our 100m² basement pipes in 4hours, and that was with a dodgy pipe stapler.

[JohnMo]

4 hours ago, Conor said:

Stapling ufh pipes into PIR is easy. We laid our 100m² basement pipes in 4hours, and that was with a dodgy pipe stapler.

I just used my thumb to push the staples in

[Russell griffiths]

You can staple to eps, no problem I put in a couple of thousand with the staple gun. 

[Radian]

I was just thumbing through our photos and - oopsie! No plastic barrier under the pipes! Ah well, too late now ?

Edited January 24, 2022 by Radian

[pilgrim]

Ooops!! well im guessing its still working well. Hopefully that doesnt cause any problems down the line.

[JohnMo]

Aluminum reacts with the alkalis (OH) found in portland cement concrete. When these two chemicals are combined, the reaction produces hydrogen gas. ...

 

corroding the aluminium foil, but mostly causes bubbles in the cement

[Conor]

11 hours ago, Radian said:

I was just thumbing through our photos and - oopsie! No plastic barrier under the pipes! Ah well, too late now ?

 

I'm afraid the only course of action to take is to completely demolish your house and start again ?

[Conor]

13 hours ago, JohnMo said:

I just used my thumb to push the staples in

I ended up doing the same. We had a lot of tight loops so not really any slower than the stapler. 

[pilgrim]

Great thanks for the help. The next question is does anyone have any recommendations for the best screed products / levelling compounds? 

[JohnMo]

I did mine very early in the build process and used fibre reinforced C34 concrete.

[Radian]

54 minutes ago, pilgrim said:

Ooops!! well im guessing its still working well. Hopefully that doesnt cause any problems down the line.

Almost two years have passed and nothing has exploded except for the price of gas and electric. Hey, maybe I can tap the hydrogen as a fuel source...

[Temp]

Talking of exploding... Got an email from Octapus today talking about 75% increases in electricity bills.

[Nickfromwales]

19 hours ago, Radian said:

No plastic barrier under the pipes! Ah well, too late now ?

I've never bothered tbh, and I've done loads. I took up one floor ( in a failing Everest summer room extension ) and that had been screeded over foil PIR. A lot of dark patches in the foil, but no issues with the screed, and no degradation of the PIR as far as I could see. It's only an issue whilst the screed is freshly laid and curing, and once cured it all plays nicely. Only real need for membranes atop the insulation is where you are having a liquid screed or a very wet concrete pour afaic.

On 23/01/2022 at 21:52, pilgrim said:

but the building inspector did not like this plan and said he wanted me to pour more concrete in before adding insulation.

Take a core sample and see how thick the concrete is. He should have suggested this before giving that advice!!

On 23/01/2022 at 21:52, pilgrim said:

So now I am thinking off levelling off the existing concrete damp proof course, then adding 260mm of insulation, then finish off with 70mm of screed and UFH pipes.

Does this make sense?

Yes, as long as it's the correct EPS with a compressive strength. EPS comes in various 'grades' so you'll need to tick that box. I'd go 150mm EPS > 100mm PIR and 80mm screed.

7 hours ago, pilgrim said:

Great thanks for the help. The next question is does anyone have any recommendations for the best screed products / levelling compounds? 

If you want a really good screed layer, PM me and I will give you my mates details. He travels and has done all my screeding for over the years. Very good team and I've not once had to self level before tiling. All set out with lasers and to a tolerance of a couple of mm.

[markc]

7 hours ago, Temp said:

Talking of exploding... Got an email from Octapus today talking about 75% increases in electricity bills.

I got that too … not the best worded or informative email, couldn’t workout if it was a rant, a warning or just junk.

[Radian]

4 hours ago, Nickfromwales said:

I've never bothered tbh, and I've done loads. I took up one floor ( in a failing Everest summer room extension ) and that had been screeded over foil PIR. A lot of dark patches in the foil, but no issues with the screed, and no degradation of the PIR as far as I could see. It's only an issue whilst the screed is freshly laid and curing, and once cured it all plays nicely. Only real need for membranes atop the insulation is where you are having a liquid screed or a very wet concrete pour afaic.

The dark patches are aluminium oxide and while the oxidisation will have stopped after the cement curing it will have lowered the emissivity of the foil. Some additional heat will be conducted through the PIR as a result. Bit of a second or third order effect but definitely worth preventing with a flimsy sheet of polythene. We live and learn.

[JohnMo]

Emmisivity without an air gap is next to nothing.  So the foil would act as a conductor anyway.

[Iceverge]

On 24/01/2022 at 08:29, Russell griffiths said:

You can staple to eps, no problem I put in a couple of thousand with the staple gun. 

 

Hi Russell,

 

Can you elaborate on this please. What grade of EPS and staples did you use?  I'd prefer to avoid PIR if I can for future projects.