Different ways to level existing concrete basement slab for new floating floor assembly?
Seattle, WA 4c
Trying to figure out a good way to keep an existing basement slab, and build a floating floor assembly above. The current slab (if you would even call it that) is of various condition and build – when the house was first built in the 20’s there was no slab, and between now and then different sections have been filled in with different thickness/mix of concrete, and there is even one small bare patch of dirt. the slab/floor also has a variance in elevation/height by some 2-3 inches. Originally we were thinking of taking this slab out and replacing it with a new slab (level grade, gravel base, poly, 6″ foam, and new concrete). But now I’m trying to save a few bucks and use as little of new concrete as possible so I thought this could potential be a good place for a floating assembly (gravel base, vapor barrier, less foam [save some head height], 3/4″ subfloor, and 1/2″ uponor quick trak panels[radiant heat]).
Two main questions:
1.) Am I right to think this is a possible assembly in this situation? No load bearing walls will fall on the new floor assembly, just some new partition walls, and some appliances/furniture. One concern of mine is I’ve read that for a floating subfloor to work it is important to have well compacted soil below – since I don’t know what the condition of soli is below the mess of existing slab.
2.) What is a good way to establish a level base for this assembly – can gravel be levelled and built off of, or should I pour some concrete over the existing slab to get a level base?
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