DIY Doctor UK DIY Forums

I have a concrete foundation slab base.

Looking at putting down insulation but everywhere it says this should be 70mm thick then on top of to put tongue and groove chipboard.
However I don’t have 70mm of height between the door into the flat and the slab base. It is more like 35mm.

Is there a thinner alternative to 70mm of insulation or another way of getting the right amount of insulation down and still leaving room for a solid underfloor and then flooring to be put down without having the front door obstructed.
Or would raising the threshold into the property without restricting the head height too much be the way to go
Or would that have its own restrictions under building regs.

Hi swan99,
Raising the door threshold could be quite expensive, how about having a sunken area inside for the opening arc of the door - use 10mm PIR insulation here. Then have a step up to the remainder of the flat where you could use thicker PIR boards.
Regards S

I think because of the layout it wouldn’t be practical. The hallway isn’t large enough to not end up with stepping down and then up again when walking between rooms.

I would worry about it being a potential trip hazard

I was hoping that there was some ultra thin insulation that had the same effect as the 70mm sort

Hi swan99,
You say there is 35mm clearance under the door - if you used 12mm PIR and 18mm chipboard flooring you would have 5mm for your floor covering.
12mm PIR is not going to have anything like the insulation effect of 70mm, probably not worth the expense.
Regards S