bathroom floor underlayment near bathtub
caseyr
| Posted in Construction Techniques on
What do I put into the crack between the existing tub and the Hardibacker on plywood that I am adding to the subfloor? Do I just use a silicon caulk with/without a backer rod or something entirely different? The subfloor is 2×8 tongue and grooved wood.
Related question. The tile people I have talked to don’t use a moisture resistant membrane in the bathroom under the tile. The books I have skimmed about tiling bathrooms all seem to list a membrane on top of the Hardibacker and under the tile. Any thoughts as to the desirability vs extra hassle of a membrane?
Replies
I would fill a crack like that with whatever you are laying the tile with, assuming it isn't over 1/2" or so.
A little confused about the membrane over the tile-backer board. How will the thin-set stick to the tile-backer and bond the tile?
The membrane should be under the tile-backer if you use one. If the floor isn't getting soaked it should be okay.
Make sure the tile is thoroughly sealed after the thin-set / grout is cured (directions on bottle).
Also the line between the tub and the tile could be color-matched caulk (sanded or non-sanded) that is sometimes made available by the grout manufacturer. The caulk (as opposed to the grout) will reduce cracking at the tub line when the tub is filled and / or heats up with bath water (expands / contracts). Good luck.
What do I put into the crack between the existing tub and the Hardibacker
Cementitious material - Synco comes to mind. Essentially a fine cement mixed with water, trowelled into place. Read the directions, tho'.
a membrane on top of the Hardibacker and under the tile
The brand escpaes me right now, but there is a composite that is stuck to the subfloor and has a 'furry' top to which the thinset adheres. Expensive, tho'. Unless you intend to play submarines in the tub and swamp the floor, ignore the membranes. Instead apply a sealer to the grout (helps keep it clean as well)
All the best...
To those who know - this may be obvious. To those who don't - I hope I've helped.
I would not use grout against a tub. Toomuch chance it will crack. Use a color matched caulk.
In a bathroom you only need a membrane where it has to be waterproof, like inside a shower or tub-shower. For a bathroom floor, or around a tub-only (no shower) then there is no reason for a membrane.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
You might be thinking of a product called Red Guard, which is a latex film that is brushed/rolled on pink and dries red. You would apply this over Hardibacker / cement board / concrete / flooring then apply thinset and tile directly to it. The latex membrane will keep water from getting into your backer materials and flooring. Use it on the walls and floor.
As a parent of two small kids, I know FOR SURE that they can easily splash gallons of water out of a tub without even trying.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
The reason that I am considering a membrane is because water has spilled onto the bathroom floor and caused problems where the floor meets the tub and wall. It is a fairly small area, so perhaps I will just paint a the area of the floor of about a square foot or so when I fix the floor prior to laying down the plywood. Having the membrane over the backer board seemed strange to me too, but two different tile books showed cut away drawings with the backerboard then thinset then membrane then more thinset and finally the tile. One of the tile books talked about a combination islation and water resistant membrane but the drawing showed the membrane over both a concrete floor and a wood floor. Sounds like perhaps the thing to do is to put the thinset right up to the tub but finish it off with a topping of good caulk.
The floor of your bathroom isn't going to be like the bottom of a tub. You just need to keep water that does get on the floor from seeping through to the subfloor.
On the installs I have done, I keep the hardibacker about 1/8 away from the tub, then fill the gap with GE type-II silicone caulk. I make sure the caulk is smoothed in all the way and has adhesion to the tub and backer board. I lay the tile, again with about a 1/8 gap, then fill that gap will color-matched caulk, so it wont crack.
I am pretty sure this method is going to keep water on the surface of the tile and away from the wood.