Natural slate flooring?

Question

My kitchen floor is half concrete and half floorboards, I have been told 2 different stories of how to put the natural slate tiles down on this. 1 says the tile can be put straight over the floorboards and concrete with a special adhesive, the other says it needs board down first on the concrete and floorboards, which is right. also in the shop the tiles werent sealed and they looked really different to the ones we got even though they were the same tiles. He said its because the shop ones hadnt been sealed. Do we have to seal the tiles as they looked nicer without the sealer they looked more natural. Or could we wait until they were worn a bit then put sealer on.

Answer 1

Hello Janet,

You definitely want to put down a tile underlayment (be it a cementitious backer unit like Wonderboard, Durock, or PermaBase; or a fiber cement/gypsum underlayment like Hardibacker, Denshield, or Fiberock) to raise the height of the plywood subfloor to reach the concrete AFTER the hardwood flooring has been removed.  You need to address the joint where these two dissimilar materials meet with a crack isolation membrane, the easiest being Redguard at HD.  You'd still need to leave an open joint to be caulked at this intersection, most colors of grout have a coordinating textured caulk.  Some stones do come with a presealer on them, but I haven't ever come across slate with one.  It is usually the roughest packed/shipped stone, so I can't see there being a sealer.  Best way to tell is to apply drops of water to the surface and see if it beads up.  THERE ARE penetrating sealers that fill the pores of the stone yet retain the natural look.

Answer 2

you can get a hard concrete based Bord for tiling. i would be tempted to use this. you can get a special adhesive for wood floors but i think that this is still open to movement. as for the sealer. this is to stop staining. you can leave it natural but if you spill oil on the floor it will never come out. the risk is up to you.

Answer 3

Can you explain a little further about the "floor boards"?

Do you mean 1/2 of the kithen is on a concrete slab foundation, and the other 1/2 has basement under?

Answer 4

you will have to use an underlay on the timber floor part. Also a control joint will be required between the timber floor and the concrete floor. The sealer part is up to you. How you do the floor IS real important. Tiber floors are no stable and that is why you put a cement board down etc

Answer 5

I would definitely use a concrete board provided you have a sound, level foundation.  That way you would only have to deal with adhering the stone to one surface type, not two, and you wouldn't have to worry about some "wonder adhesive" not working consistently.  You can also bridge the joint between the wood and concrete with the board, which will protect your grout from cracking from possible expansion along the joint. Backerboard is cheap and easy to install -- a small investment to ensure the success of a much larger one.  Also, I would seal all natural stone and grout to protect them from stains.  If the sealed color isn't right for you, you may want to look at another rock or maybe a synthetic one.  Good luck!