Q: If we install 3/4″ x 8″ t&g solid wood, wormy red oak (finished in place) floors in the non-conventional, non-recommended fashion of fully adhering the boards over a structural concrete slab, using Sika’s T55 adhesive.. and if we have no moisture drive problems from the slab and also have a well functioning humidity control system in place in the home, how likely is it that we will still experience cupping of the wood floors?
A: Cupping occurs when wood absorbs moisture faster than it can release it. The subsequent side pressure against the other boards or structure assists in pressing on the board edges and cupping results. You must be very confident in the concrete slab, your humidity control and the milling of the boards to even think of doing this. Unless the boards are all arrow straight, how are you going to pull them tight and keep them that way during the installation? This might work, but I wouldn’t bet the farm on it. I think I would install appropriate sub flooring and nail it down, and mix another width in the mix. I would also glue the end joints of the wider boards.