How do insulate a basement slab that is sloped ?

Louis-François Lapointe
Louis-François Lapointe
Updated: Nov. 12, 2020

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 !

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