100mm Celotex PIR boards for UFH have warped, is there a solution?

[Stuart X-Ray]

We started to renovate our 200+ year old stone cottage nearly six years ago. Complete roof replaced so it's dry inside. Excavated the floor out inside down about 300mm to install a solid, insulated UFH system with ASHP. The project stalled due to Covid and the PIR boards have been in storage for 18 months. The intention is to construct a ground floor consisting of: base rock, about 20-50mm blinding, DPM, 100mm C20 concrete, vapour barrier, 100mm PIR, second vapour barrier, UFH pipes stapled through patches into PIR, 50mm pumped screed, quarry tlies.

We are currently putting the DPM down, concrete pour will be in about a month from now.

However, we uncovered the Celotex GA4100 and every sheet has bowed/curled up by 10-20mm, all in the same direction. Can we slice them into strips and foam gun together flat or do we scrap them and buy new, if so which ones won't curl up?

Has anyone had to deal with this before?

Has anyone had this happen after the floor was laid? The thought of the screed lifting up by 20mm is a bit scary.

Any advice would be welcome.

Thanks,

Stuart.

[Carrerahill]

21 minutes ago, Stuart X-Ray said:

We started to renovate our 200+ year old stone cottage nearly six years ago. Complete roof replaced so it's dry inside. Excavated the floor out inside down about 300mm to install a solid, insulated UFH system with ASHP. The project stalled due to Covid and the PIR boards have been in storage for 18 months. The intention is to construct a ground floor consisting of: base rock, about 20-50mm blinding, DPM, 100mm C20 concrete, vapour barrier, 100mm PIR, second vapour barrier, UFH pipes stapled through patches into PIR, 50mm pumped screed, quarry tlies.

We are currently putting the DPM down, concrete pour will be in about a month from now.

However, we uncovered the Celotex GA4100 and every sheet has bowed/curled up by 10-20mm, all in the same direction. Can we slice them into strips and foam gun together flat or do we scrap them and buy new, if so which ones won't curl up?

Has anyone had to deal with this before?

Has anyone had this happen after the floor was laid? The thought of the screed lifting up by 20mm is a bit scary.

Any advice would be welcome.

Thanks,

Stuart.

What happens if you stand on one? From experience they just flatten. I am sure with 100mm of concrete on top of them they would soon lie flat. They do shrink within the first sort of 3 months. I remember reading somewhere that you are meant to use boards that are a minimum of 3 months old so that they have gone through initial shrink. I have seen fresh boards installed all shrink and end up about 3-4mm short whereas they went in tight which was a bit worrying.

 

I would not scrap them, I would just look at options to pull them down flat, maybe a saw kerf along the mid-section might help. 

 

They are not going to be lifting 100mm of C20 concrete!

 

 

Edited March 16, 2022 by Carrerahill

[Russell griffiths]

First thing to do is stop and re look at your figures. 

100mm with ufh is a bit inadequate really. 

Look at adjusting your levels so you can get more in. 

Scrap the sand blinding layer and replace with 50mm of eps, it will deform and form a nice surface for you dpm. 

Regarding the pir, bring it home and stick two scaffolding boards on it with a couple of concrete blocks on top, in a week it will be flat again. 

[Stuart X-Ray]

We are a bit limited on the depth, base is solid rock in places and so we can't dig down deeper. the blinding which is done now, is from about nothing to 50mm depending on rock shape. Actually we've set cable ducts and a land drain below the DPM for ground floor electrics and prevent the under ground stream from flooding us.

Standing on the boards doesn't seem to move them at all but we will try clamping for a couple of weeks to see if it works. I'm thinking that slitting them might be the answer. BTW the 100mm of concrete is under the PIR, there will be 50mm of pipes and screed on top.

[Stuart X-Ray]

[Andehh]

Did it all go smoothly? 

[Stuart X-Ray]

On 16/03/2022 at 19:30, Andehh said:

Did it all go smoothly? 

Not yet, we are still trying to get the DPM to fit round all of the corners, because nothing is square it's tricky to make a hospital corner fold. We have 18 inside corners and 16 outside corners to form on the DPM. The Celotex issue is still not resolved and wheat I found so far is worrying. The boards have shrunk on one side only by 5-10mm and that's why they have bowed. Celotex can't tell me why but there are loads of cases on line where this has happened mostly in walls and roofs where it has become loose or called out. It is way to stiff to straighten without cutting it. So we may need to scrap it and get something else, probably Kingspan, certainly would not touch Celotex again for UFH.

[Conor]

Can you them on flat ground with a length of timber at each end and stack a few concrete blocks in the middle to take the bow out? We had a few dismantled IKEA wardrobes in storage and the same thing happened to the sides and doors. I set them on the ground on top of 4" timbers at the ends and set a block on the middle. Worked a treat. You might need a bit more weight tho.

[bassanclan]

You could lay 175mm pir then fit pipes to the pir and then pour self levelling liquid concrete 65mm thick for a similar build up thickness,much better u value and much less concrete cost.

[Russell griffiths]

You can be better off making the corner folds from a separate piece, cut a piece 1m x2m and do the fold, then lay your dpm over the top of the pre made corner and tape together. 

Far easier, or just cut a relief cut and tape.