[lynxpilot]

Our small log house has pine floors made from low quality slats and was constructed very poorly. To add to this, the under-floor supports (joists and crossbeams) were cut by the owner builder from trees on the property and installed without any drying. Joist spacing is 16" ctc, but I suspect that the movement of the main members over time as they aged has contributed to the uneven nature of the floor in general. I've purchased laminate to install over the pine as well as feathering compound to stay within the laminate tolerance of irregularity. The more I think about it, the more I'd like to just slather a light coat of SLC and lay 1/4" cement board over it, followed by the underlayment and laminate. I only need about 1000 sq ft after I discount bathrooms and other areas that wouldn't get the treatment. Any reason not to do this for the additional stability/flatness?

[rusty baker]

CBU offers no structural support at all. Better to use plywood.

[lynxpilot]

OK, thanks.

[DannyT]

if you use slc it needs to go on top of the cement board. plywood first then cement board set in thinset and screwed down with proper screws. if you are just putting laminate down you really don't need the cement board.

[JetSwet]

Huh?!?... It's laminate not tile. If the floor isn't level or flat pull up the existing ply.