Gaps in celotex floor insulation

Joined
18 Feb 2026
Messages
3
Reaction score
0
Country
United Kingdom
Hello all

Thought this would be pretty obvious but came home from work yesterday to find the builder has laid the floor insulation in my new extension and seems to be large gaps everywhere…. I thought the joints were supposed to be butted up tight together… some of the gaps look 20mm wide along the whole length of the board in places…. Should he replace some of them? I wouldn’t imagine expanding foam for this many gaps was a good idea, and not comfortable having screed laid where there is these gaps, surely it would affect the structure over time?
Any advice welcome, pics attached
Thanks
 

Attachments

  • IMG_9816.jpeg
    IMG_9816.jpeg
    738 KB · Views: 24
  • IMG_9819.jpeg
    IMG_9819.jpeg
    1,020 KB · Views: 23
  • IMG_9818.jpeg
    IMG_9818.jpeg
    634.1 KB · Views: 23
  • IMG_9817.jpeg
    IMG_9817.jpeg
    748.2 KB · Views: 22
It's not acceptable. If the concrete gets under the insulation, despite the membrane, the insulation could well float up.
There's no excuse for it not butting up.
I wouldn't accept it.
If it's tongue and grooved, and that prevents butting up, it's been installed wrong.
It's just a matter of flipping some of the boards.
 
Agree it's not acceptable, also once he's redone it and you've seen it or seen photo evidence check the membrane is sealed where its joined else screed may seep through the gap.
 
Hello all

Thought this would be pretty obvious but came home from work yesterday to find the builder has laid the floor insulation in my new extension and seems to be large gaps everywhere…. I thought the joints were supposed to be butted up tight together… some of the gaps look 20mm wide along the whole length of the board in places…. Should he replace some of them? I wouldn’t imagine expanding foam for this many gaps was a good idea, and not comfortable having screed laid where there is these gaps, surely it would affect the structure over time?
Any advice welcome, pics attached
Thanks
Poor. 3/10.
 

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top