First time tiling

yochujr

I am getting ready to begin my first tiling job in a fairly small (narrow) bathroom. The tiling that's currently in there is starting to crack and the grout it popping out which I contribute mostly to the underlayment. When installing hardwood floors throughout, I noticed that there was 1/2" layer or plywood subfloor with 1/2 particle board underlayment on top. For the wood, I removed all of the particle board throughout and replaced with plywood.

My questions are, when I remove this particle board, should I replace with 1/2" plywood and then put something like a durarock on top? I so, what thickness should it be and will this added thickness cause me issues when I go to put the toilet back in?

Also, do I use a particular mortar to attach the new underlayment? I've read to tape and mud the seams. Should I just use mesh drywall tape and mortar?

Again, I am pretty handy but this will be my first time attempting a tile job so any advise is greatly appreciated. Thanks in advance!

JazMan

Hi Yochujr, how do you pronounce that? (I thought my real given name was unusual). Give us a name to call you by.

As you probably know by now, particle board is the worst possible type of underlayment or subfloor ever used. If the tiles were stuck to it directly, it never had a chance.

So, the 1/2" ply is the subfloor and the particle board is the underlayment? Are you positive the ply is only 1/2"? Did you measure it or did you read a stamp from the underside? 1/2" ply measures less than 1/2", could it be 5/8"? How old is this house? I'm guessing it was built in either the '60's or 70's.

Once the PT is at the curb, you can evaluate the condition of the subfloor and decide then. I don't think I would remove the subfloor unless it's in sad shape. The subfloor is under the walls and so you'd have to cut it short of the walls, then install blocking to support both the new and old layers.

If you remove the old subfloor, replace it with 3/4" t&g subfloor, otherwise go with 1/2 or 5/8" underlayment grade ply. Then you should install a concrete backer into thin set etc. or a membrane such as Ditra.

No big deal. Yours wouldn't be the first time. They make shims or you can use a thicker or even two wax rings to seal the toilet.

You're talking about the concrete backer now right? Durock or Hardie. CBU manufacturers want you to use a modified thin set (powder) to install tiles, most also suggest the same to install the board. So, get modified thin set mortar. Probably one #50 bag. Use the special alkaline resistant fiberglass mesh tape, proper fasteners.......

You should also run the framing specs at us to make sure the joists and framing are sturdy enough for tiles. BTW, what type of tiles?

Jaz

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yochujr

JazMan, thanks for all the great info. My screen name is actually a combination of my last name (Yochum) and my initials. I use it on a lot of forums and probably should have given it a little more though, haha. Feel free to call me Jason.

You are correct, the ply is the subfloor (installed under the walls) and the underlayment throughout the house is particle board installed after the walls were framed. I learned this the hard way after already purchasing enough hardwood to do my intire first floor. It was a lot of work but I took the time to do it right (removed the pb and replace with 1/2" ply) and it turned out great.

I don't recall if the subfloor is exactly 1/2" thick but when doing the hardwood, it all seemed to be in relatively good shape with the exception of a few squeeks from loose nails. In a perfect world, I would like to just tear out the pb and replace with 1/2" ply as I've done in the past, and then add 1/4" underlayment of some sort. Then figuring about 1/2 inch thick for mortar and tile, I should be almost dead even with the thickness of my finished wood floor although I did not take into account the mortar used under the cement board.

The tile I am using is a ceramic tile that I measure to be 1/4" thick and it's 13" x 13".

It appears as though I still have a lot to learn as far as different mortar mixes and where to use them but hopefully I've got the right idea. I can also send pics of the current floor if that would help. I'll try to get all the specs on the joists as well.

If I'm way off on anything or if you have any alternative ideas to save me any time, money, extensive cursing please help me out! Haha, and thanks again for taking the time to help.

yochujr

Alright, just went to the basement and measured and it looks like I have 2x10 joist, 16" o.c. with about a 16' span. As you walk into the bathroom, the floor joists will run left to right. The main support beam would run front to back and is basically directly under the tub or just to the back side where is meets the wall. Basically, the tiled area would be about 4 1/2' wide (wall to tub) and 9' deep (minus the footprint of the vanity). The joists are also notched on the bottom where the drain pipe goes through so hopefully that doesn't cause a huge problem.