Is 3" thickness really enough for a basement slab?
Hallelujah! 1" XPS board is down, so is the StegoWrap vapor barrier, the rebar and soon the 6"x6" wire mesh. So the new basement slab in the old wet basement will be poured on Monday. It already smells better!! (Might have something to do with discovering and fixing the broken sewer pipe just outside the foundation, that was draining back into the gravel basement floor - yuck!!). Today I reviewed the diagram on "How to Finish Exterior Foundation Insulation" and it shows a slab thickness of 3". My concrete guy insists on 4"; however, to make it all level it's really going to end up being 5" in places. Unfortunately that means that the new floor will be an inch higher than the one in the connecting room.
Really, a 3" thick slab? That would solve my mismatched floor levels. BUT... what about:
...The inevitably imperfect stone levels underneath, detected when walking on the blueboard;
...The drainage tile network (and I mean network) underneath, bedded in the stones (yes, surrounded by stones and filter cloth burrito) potentially causing flex due to their hollowness.
Seems to me the rebar network (set on plastic chairs at 2 1/4"; cross bars atop that adds another 1/2 more height) topped by 6x6 mesh could offer plenty of stability/strength but all that stuff needs enough concrete around it. Hence the 4"+.
How can the 3" in the diagram be enough??
Posted Nov 19, 2010 8:15 PM ET
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