Hi everyone, I’m after advice on the correct steps for the following desired outcome. We are converting half of our garage into an internal room. The current concrete floor is uneven, slopes into the middle of itself probably by about 100mm from the sides. Not sure on dampness but the garage is single skin currently on two sides. The garage floor is also roughly 250mm lower than the house we want to level it with. Question I need help with is: Are these the correct steps to take to complete the floor before carpeting? DPM SLC (to even the existing floor) Insulation boards (150mm Celotex or similar brand) SLC or Screed poured directly over the boards Carpet underlay I am in no way experienced with this but the above is what I’ve cobbled together from other posts online, so looking for confirmation on those steps and any advice if I’m way out. Thanks everyone!
Waterproof SLC to level out the concrete floor 150mm Celotex 18mm or 22mm T&G chipboard boards glued together but leaving a 5mm gap between its edge and the walls Finished flooring
Thanks Rogerk101 - how would the board be secured to the insulation and would the floor be almost spongy to walk on without the solid top layer?
If the solid base is perfectly flat (which it would be thanks to the SLC), the insulation itself is rigid enough not to wobble or feel spongy. However, with the 22mm chipboard (even with 18mm chipboard) on top, there is no way you'd feel any sponginess. In fact the floor would be more solid feeling than any upstairs floor based off 200mm timber floor joists spaced at 400mm centres.
It isn't. It doesn't need to be. It needs to be able to expand and contract with changes in humidity and temperature and it will do that at a rate that is different from the insulation, so micro movement needs to be enabled. If you did decide to glue it to the insulation with some sort of adhesive, the inevitable movement of the chipboard would simply rip the insulation, which doesn't provide much resistance to shear forces. You do need the 5mm gap around the edges though, otherwise the chipboard risks buckling.
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