Floor Settlement PIR Insulation

noc32

We did up a semi d last year which included an extension also. Moved in Jan 2016 and everything was fine. Since April however, I noticed gaps starting to appear between skirting and finished floor. Builder and Architect were made aware and we've been monitoring the progression since. By November 2016 gaps range between 5 and almost 20mm in places. It doesn't appear to be a structural failing. A raft foundation was used for the extension part versus a 100mm concrete subfloor in the existing part of house. 55mm easy flow screed over insulation contain UFH pipes. The gaps though are across old and new. Common denominator is the floor insulation used. Although 200mm EPS insulation was specified, 240mm PIR boards (2 layers of 120mm) by a reputable company were used instead. Reps from this company have been out to inspect and have offered to make a contribution toward remedial works (which I find odd). Anyone else hear of similar cases or have similar story to tell?

Metric Tensor

If they offered to make a contribution with no argument it's a known issue - however 50mm of screed is very little!! Have you big heavy stone tiles it something similar on the floor?

Would appreciate knowing the brand of insulation (by pm) so that I can see if we used it anywhere.

noc32

Metric Tensor wrote: »

If they offered to make a contribution with no argument it's a known issue - however 50mm of screed is very little!! Have you big heavy stone tiles it something similar on the floor?

Would appreciate knowing the brand of insulation (by pm) so that I can see if we used it anywhere.

55mm screed was supposed to be optimum depth, thermally speaking. Gaps occur whether finish is 12mm tile or 12mm laminate flooring, so not weight related I think.

Metric Tensor

I've heard anecdotal stories before of air "escaping" from PIR slabs and the slab then shrinking because of this but I can't say I've seen it personally.

Any chance there's some left over slabs thrown about in the garage or somewhere that you could have a look at to see their condition?

noc32

Metric Tensor wrote: »

I've heard anecdotal stories before of air "escaping" from PIR slabs and the slab then shrinking because of this but I can't say I've seen it personally.

Any chance there's some left over slabs thrown about in the garage or somewhere that you could have a look at to see their condition?

Builder thought it was air gaps between boards escaping over time. Hard to explain 20mm tho. Unfortunately, no left over pieces unless builder has any. Ill ask him. Good idea. Thanks

Water John

This is a retrofit on the main house? Then there is vertical insulation around the perimeter, probably 25mm, in each room. The skirting board would largely cover it in the new extension. Depends how far out from the walls the cut was made in the original building, to put down the new floor.
55mm screed should be fine, would prefer 75mm but should not matter.

sydthebeat

What was the existing floor make up please?

Did you keep the finished floor level the same as the existing?

noc32

sydthebeat wrote: »

What was the existing floor make up please?

Did you keep the finished floor level the same as the existing?

Yes, floor level is same across existing and extension areas. Existing floor was suspended timber floor. These joists were taken up and replaced with compacted hardcore, radon barrier and 100mm concrete subfloor. This then matched the level of the 175 deep raft slab in the extension. The 240mm insulation layer then ran throughout existing and extension areas. Dpm over, then 55mm liquid screed containing the underfloor heating pipes. Tiles and laminate flooring finish. Gaps occur in both old and new areas. Floor level is moving relative to fixed items built off foundation such as door frames, stairs etc.

kieran.

Have you any pictures of the gaps?

delfagio

Unless when you removed the existing timber joists and installed hardcore, radon barrier and 100mm concrete slab either two things may have happened.

1.) The hardcore was not correctly compacted which has resulted in the 100mm concrete slab, 240mm insulation and 50mm floor screed sinking somewhat.

2.) That the existing ground onto which the hardcore was placed does not have suitable enough bearing capacity and has began to sink with all the added weight.

Was the 100mm concrete floor individually placed in the existing house ground floor rooms. As in, each room was dug out, hardcore placed and 100mm concrete slab installed but the slab in each room are independent and not tied to each other??

sydthebeat

240 mm of PIR insulation is not going to sink 20mm due to the weight of 55mm of an easy screed.


as above, this is much more probably a structural failing due to either
1) inadequate depth and / or compacting of hard core under floor slab AND raft foundation.
2) bad bearing capacity of the ground

or possibly
3) external works around the site such as reopening of drains or extensive drainage of surrounding lands.

It is surprising the material providers offered to make a contribution towards remedial works, but lets see if they follow through with this if the remedial works cost €10k's