How do insulate a basement slab that is sloped ?
Hi everyone !
I have a 30x30 basement that I want to finish (on a budget). We live in zone 5a and the house was build in 1950. Normally I would've covered the slab with dimple membrane, 2" XPS and osb/plywood achored with tapcons. The problem here is that there's a significant slope to a central drain (4" at the lowest). I will be removing that drain and other old cast iron pipes. If I level with sleepers, there will be multiple breaks in the insulation.
My ideas was as follow : fill the sloped cavity with crushed stone trying to get it as level as possible, cover it with vapour barrier, add 2" xps and then subfloor.
Is there a better way to do this ?
Thanks for your help !
The best way to insulate a basement floor that is not currently level would of course be to first level it. In your case though, as it is sloped to a drain, do you have another plan to deal with any bulk water that may accumulate on the floor? If you were adding stone to bring it to level, would you not want to leave the drain, or is it not working at this point? I’m wondering what your plan is to deal with any potential bulk water that may accumulate, do you have a sump pump?
But for the meat of your question, yes, you could level it with stone, I would get small stone to make your job easier, like 3/8ths perhaps. If the drain will no longer be in use, you could also do it with self levelling concrete.
As for finishing and insulating, yes, a vapour barrier at that point would be necessary as there would not have been one with the initial construction.
The sleepers would mean a break in the insulation, but if you don’t have them you may find the floor rather spongy.