subfloor

has anyone had success floating luan over concrete before laying lvp?

never even heard of that

you would have to put a moisture barrier

what holds the sheets from rocking over the highs and lows in the slab?

ONCE in my ~40 years of flooring installs I glued down some 3/4" ply over concrete with an extra thick tar like adhesive. The boss also made be drive concrete nails to hold the ply down whilst the glue dried. I think we were installing parquet overtop and we were raising the subfloor to meet ceramic.

Thin set and 1/4” backer board. Throw some tap cons in for good measure, or just use tap cons in the first place.

Luan won’t work for much of anything except some arts and crafts…

C.J. said:

Thin set and 1/4” backer board. Throw some tap cons in for good measure, or just use tap cons in the first place.

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That’ll work if the concrete is flat and smooth and you countersink the tap cons.

We do it a lot here. Rather than demo tile down to the concrete, you fill in the low areas (carpet) with backer board to flush out with the tile. Little skimming and a little grinding then you float a floor right over all that mess.