2nd floor renovation. First set of contractors did a bad job with joists, its a long story. Structural engineer helped us get them to fix it, but the subfloor still had a slope of 1 3/8 over 10 feet, plus a lot of dips and waves.
New contractors decided self-leveling compound would be too heavy for the floor. We already had almost 2 in. of subfloor; they put in another layer of plywood, shimmed, to even things out. Great. Seemed fine. But at the perimeter, where I guess they couldn't get the right thickness plywood, they evened it out with thinset, bridging two pieces of plywood to get it all level.
The thinset doesn't exceed 1/4", thankfully, bc I read elsewhere that anything over that is asking for trouble. But I am troubled that they used thinset. This job got expensive for them and me so I get why they cut costs with thinset, but I've never heard of this. We're putting laminate over the floor, not tile.
3 concerns: overall is this strategy a bad one? also, expansion joints. There are few expansion joints between the plywood sheets themselves and now thinset in some areas covers what expansion joists there are. is that a big problem? my fear is that I'm going to end up with a crunchy, sandy floor. also--is it true that shimming another 5/8 of plywood over the other 2 inches is less weight for the joists than just pouring self leveling compound.
please help us figure this out. we've had a lot of bad experiences with our house.
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