Need some insight on project

17 Oaks · Aug 2, 2017

Ok, stripped upstairs bathroom to the studs. Something about bright white tile from floor to the top of 12' ceiling + 2 skylights that forces you to put on a pair of Ray Bans and a pair of Foster Grants to keep from going blind when you walk in.

here is the issue:

Turns out there is not floor under the tile, all there is is the sub floor (wood, single layer). The tile floor was laid on concrete backer board ( and same on the walls except in the shower and it was on drywall).

I am going to put tile down on the floor (NOT white) and since its only a subfloor should I reuse concrete backerboard, if so what thickness or go with OSB + thinset and a waterproof coating like redguard, OR ________???

My guess is the tile removal has created about 4000 lbs of weight based upon my 18 foot trailer and how much tile/backerboard that is on there and my past tile removal in this house over the past 5 years. This is the 3rd bathroom I have done here.

frugalangler · Aug 2, 2017

Backer board for the tile, the adhesive will stick to it much better, and it's also going to reduce flex (read: reduce cracked joints). Sub-floor is not sufficient for tile adhesive.

You can get away w/ tile on drywall, but not in a bath/shower area, it WILL absorb moisture and grow mold behind the tile. MOLD = NOT GOOD!

17 Oaks · Aug 2, 2017

frugalangler said:
Backer board for the tile, the adhesive will stick to it much better, and it's also going to reduce flex (read: reduce cracked joints). Sub-floor is not sufficient for tile adhesive.

You can get away w/ tile on drywall, but not in a bath/shower area, it WILL absorb moisture and grow mold behind the tile. MOLD = NOT GOOD!

Thanks and if you seen this place and the mold in it, you most likely like my RE Agent would have told me bull doze it down, not worth saving...but I did not and instead took it down to the studs completely, stripped out everything (even some studs) and rebuilt...YEA, and you and other are right, I could torn down and built new for less money. But I wanted to save an old family cattle ranch and that meant rebuilding the house built in 1945...

teejk · Aug 2, 2017

There are lighter weight products on the market now in lieu of that concrete. I think the technical term is "slip shield" that allows the tile to move separately from the sub-floor that temperature and humidity will want to do. We used a product called Schluter-Kerdi Ditra and I think competitors have since come into the market. It's not cheap but I think is certainly easier than cement board.

EddieWalker · Aug 2, 2017

How thick is your sub floor and how far apart are you floor joists under it?

17 Oaks · Aug 2, 2017

teejk said:
There are lighter weight products on the market now in lieu of that concrete. I think the technical term is "slip shield" that allows the tile to move separately from the sub-floor that temperature and humidity will want to do. We used a product called Schluter-Kerdi Ditra and I think competitors have since come into the market. It's not cheap but I think is certainly easier than cement board.

I am liking the less weight approach.

That said I am thinking OSB screwed down to the subfloor (wood), thinset with this (see link) on top, then mortar, then tile

Schluter-DITRA 3M Full Roll - 323 sq_ ft_ – FloorLife

17 Oaks · Aug 2, 2017

EddieWalker said:
How thick is your sub floor and how far apart are you floor joists under it?

My floor joists are 12x1's on 13'- 17" center and the subfloor is ¾ on diagonal.

The guy who built this house, there were 3 things NOT in his tool box: tape measure, level, square. Not a single square room in this house, one room out by 18 in!