im laying new ceramic floor tiles in the kitchen next week. i've already picked up some flexible adhesive and grout for wooden floors and was planning on purchasing 12mm exterior ply sheets from the local timber mearchant tomorrow. however, a mate at works just told me he has a load of 9mm ply sheets that i can have for free left over from boarding his loft (reckon it would save me £100 as its a large kitchen). my kitchen floor boards are pretty sound so i think i could probably get away with 9mm but he's not sure if the ply he has is exterior grade! is the ply likely to warp if its just regular ply? i have some floor tile primer/sealant (not pva) if that matters.
thanks in advance
thanks in advance