Hey all,

I am planning on replacing my alcove bathtub. I intend to remove only one line of tile above the bathtub so I can get it out and put the new one in. My question is, once I have removed the tile do I cut away the backerboard from behind the one row of tiles? I am assuming I will have to. Then will I need to purchase some backerboard and cut this to fit in the gap, then apply mortar and Redgard to it before I retile it? My concern is will this small section of new backerboard be water tight or am I best removing all the tiles and backerboard and replacing the whole thing from scratch? I am following my suggested route to do things quickly and on the cheap. Thanks.

 

Is there a shower in the tub area?

I think a lot depends on what you find once you open up the wall. If you have a shower I'd wait and see what was used for a membrane and if you can keep what's there. If there was no membrane I almost want to say just tear down all the tile and re-do the shower surround properly.

If there is no shower and this is just tile around the tub then again it depends on what you find. I have seen the backer extended down over the tub's flange and I have also seen it stop at the top of the flange but in most cases it extends over. If your tile is big enough you could attach a new strip of backer but I wouldn't try a strip smaller than maybe 6" and larger would be better for stability even if it requires taking off more rows of tile.

 

I do have a tap with a diverter knob to the shower head. Its a 1995 condo building.

 

A thin strip of cement board will have very little strength. It is not designed as a structural piece and relies on a full face of rigid tile and thinset mortar to stiffen it up after installation. If going this route, may want to install blocking behind to provide a stiffness to the backerboard before tape, mud and redgard.

 

How about Densshield instead? I am thinking I may just tear down all the tiles are start from scratch.

 

There is nothing wrong with cement board or Hardie Backer. The problem is if you want to install only a narrow strip. If you are now deciding to do the whole shower then there are numerous products you could use.

 

Yes I am thinking of doing the whole thing now. Would these be the right steps to follow:

1) Remove existing tiling, backer board, screws and nails
2) Apply furring strips to level out any wonky studs
3) Attached Densshield boards to studs (with rough side inwards toward bath) so that they sit ontop of the new tub flange, not overlapping tub flange, with about 1/4 inch gaps all around allowing for expansion contraction of boards. Fill these gaps with silicone seal.
5) Apply mortar in between backer boards, then mesh tape and then some more mortar over the tape
6) Apply RedGard all over backer boards (2 coats)
7) Ready to tile!

 

What exactly do you plan on sealing? if you leave a gap between the backer and the tub, you will have dead air and nothing to seal. The caulk goes between the TILE and the tub. The expansion gap to the flange is not needed and whatever gap results is left void behind the tile.

Densshield is a moisture barrier in and of itself and would be redundant to redgard over the whole thing. You may want to hit the screw heads and seams if it makes you feel better. If, however, you use a different backer board then your plan sounds fine.

 

So I removed the plate for the moen handle and I noticed that behind the tiles there are two layers (about 1/2 inch each) of what appears to be drywall. My question now is, in order to bring the new backer boards level to the current wall, is it okay, if I have to, to put two densshield boards back to back, or one drywall and then nail free glue and then a densshield board, and stick these to the studs?

 

dj322,

I see you have two threads going on the same project which is gonna cause confusion and redundancy.

Do not do #6 above if you're using DenShield, since it already has a waterproof coating on the surface.

You don't need two full layers, why not just apply narrow strips to the studs, then the full sheets.

Jaz

 

You need to replace the tub between steps 1 and 2.

 

Thanks,

I thought maybe I should apply two layers (one drywall and one densshield) as this has been done for the purposes of sound and/or fire proofing. After all, it is a condo and the wall concerned is a shared wall.

Also I was planning on applying the waterproof membrane on the joins between boards (using fibreglass mesh tape too) and over screws. I wasn't planning on using thinset mortar between joins, this guy didn't:

https://www.youtube.com/watch?v=-Ql2xnSU1b8

Or can I use kerdi tape instead on joins and corners:
http://www.homedepot.ca/product/kerd...1642-ft/928356

 

You should tape the joints in the manner the manufacturer of the board wants you to.

There is no need for additional waterproofing over DenShield unless some area get butchered.

There's no need to do what that guy does in the video. It will work however.

The 2nd layer of drywall behind the DenShield may not hurt on interior walls, but it's a bad idea if the wall is an outside wall. The vapor barriers can cause problems.

Use the proper sound insulation to reduce noise.

Jaz