Is it OK to tile a bathroom floor without using an underlayment like concrete backerboard? I just finished tiling my bathroom floor with a friend who claimed to be experienced in these types of things. I started to research tiling afterwards and saw many references to installing underlayment. We did not install underlayment. The tiles are installed over wood subfloor. The tiles are set but we have not grouted yet. Should I be concerned that we didn't install an underlayment? Will the floor be OK as long as I put sealer around the shower before I caulk and seal the tile after the grout dries?

I have two tile floors in my house, one in the bathroom which actually has a poured cement underpayment and my main entry which has the cement board underpayment, both floors were put in by the same professional carpet and tile company.My guess without being a professional on this matter is you do want some kind of cement under your tile floor weather it be cement board or actual cement and my reasoning for having a sub floor of some kind of is it would support your tiles better and more so your grout from cracking because I would think that just having wood for a sub floor you wouldn't have as good of support because wood has a tendency to give more and maybe even warp if moisture happens to get under the floor and almost for sure your grout would end up cracking not to mention your floor would probably not be level. Just my opinion and experience from having two tile floors in my own house. Have A Great Day!

The misspelled word above is underlayment not underpayment my spell check turned it into underpayment, good thing we have this wonderful technology to correct our misspelled words.

It will probably just result in problems like cracking, and becoming unleveled, and you may get rot or warping under the tiles, I wouldn't suggest doing it that way.

The underlayment is to increase the rigidity of the floor. The cement underlayment has the advantage of not being subject to water damage and its probably cheaper than plywood. Prior to its coming on the market, 1/2" plywood was typically used over 3/4" plywood subflooring. You said you installed over the subflooring. If you actually meant the 3/4" subflooring you will probably have problems with cracking. If you ment the previously installed wood sheathing over the 3/4" subflooring, you should be fine. In other words you need a total 1 1/4" flooring beneath the tile.

Being in the trade myself, I would only agree with hkstroud's answer. If the total height of the floor is not 1 1/4", then it would be best to rip up (not the answer your wanted :confused:), and put a subfloor down.
You can use any types available; there's cement backerboard, construction grade plywood, steel mesh with a poured cememt mixture, or my personal favourite, DITRA. This subfloor not only is easy to install, but it works very well, almost no matter what the floor underneath is like.
So I guess the moral of the story is to always check BEFORE you have an "expert" buddy come over and help you out.

Hopefully this helps
Matt
SeilingsFloors

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