Help - 97mm joists but 100mm celotex (inc picture)

[TomBowyer]

Hi,
I've made a mistake and could really use some advise how to best rectify it... Due to lack of funds i'm replacing my suspended timber floor myself

I've ordered and fitted 47mm x 100mm joists. I also ordered 100mm celotex, the idea being it would fit perfectly with the joists (I understand there may be sleight variances in places, but generally should be fine).

However - ive just measured the joists and they are all 97mm, not 100mm, so the 100mm celotex is 3mm deeper than the joists which means the chipboard flooring wont be resting on the joists it will be resting on the celotex (see picture).

What should I do?
Why would the joists ALL be 97mm not 100mm as ordered, is this standard in the building trade?
If I just carry on and screw down the chipboard will the celotex compress and be ok, or will it make the chipboard work loose over time?

Thanks really appreciate it,
Tom.

 

[catlad]

Yes that is normal, and are you sure you can make a floor with those joists. If you screw them down like that the insulation will get pushed down through the other side of the joists will they not.