Kids Bathroom

[wagsgt]

Hello all,
Recent demo'd kids 5x8 bathroom. This is a tub/shower, everything will be replaced, membrane shower walls. Floors are OK for porcelain tile. I have some general and planning questions for now. Or questions I cant find clear answer on from months of searching.

1. Does the black parts of subfloor need replaced? If I poke with screw driver they are barely softer than other areas, but not mushy,etc. I will be installing Ditra and possibly second layer on 1/2" ply

2. According to videos and posts this is the waterproofing plan: I stop the drywall/CBU short of tub flange, caulk that gap. Then run a membrane product down over that and attach to tub with kerdifix,etc. Finally caulk gap between tile and tub. But if water gets behind tile, where is it going? Wouldn't it be the same theory as exterior trim and such you leave bottom open for water to run out?

3. Could you run kerdi band between the tub and floor transition to help with splashing out the tub? I dont see how this is possible since you would only have about 3/8" area where tile would hide it? Just trying to think of a way to help prevent against future water spilling out.

4. Previous tub was 30" wide. I was thinking of adding 32" tub since I have 18" to center toilet from previous tub. The joists run perpendicular to tub drain and are notched about 1" deep to accommodate. I would need to notch another inch or so over. Any problems with this or problems with upgrading size of tub?

5. Tub area is framed 60 1/2". Can I add shims to just the flange of tub to secure it or do I need to shim entire wall?

6. Still undecided about using drywall vs CBU for tub/shower area. If I was to use CBU how do I deal with the transition where drywall meets CBU? If it was taped and thinset, do you sand and paint thinset?

There will be more but that's it for now. Thanks!

[leon82]

you definitely don't want to tile over the osb.

If its a kids bathroom waterproofing the floor would be a good idea.

[cx]

1. What is the thickness of the subflooring? What is the joist spacing?

I would not tile over water damaged OSB without at least the second layer of plywood.

2. There is no advantage to caulking between wallboard and tub and some disadvantage. If you're using a sheet-type direct bonded waterproofing membrane and can attach it to the tub's tiling flange with Kerdi Fix or similar pookey, that's fine over an open gap there.

I am not in favor of the flexible sealant (or caulking) between tub and tile, but that's the current tile industry standard. I would want at least some weep holes in the sealant if that's the way the joints were to be filled.

3. You could do that and bond the membrane to the tub in that narrow area. Won't be a guaranteed fix, but it might certainly help. You would need something to bond the Kerdi to on the subfloor, thouigh.

4. The maximum notch allowed depends upon the joist size and location within the joist span. We know neither.

5. Not sure I understand the question. What size is the tub? Where does it fit in this opening?

6. Hopefully you would make the transition somewhere outside the wet area and treat that joint as a drywall joint.

My opinion; worth price charged.

[gwrussp]

CX when you say weep holes are those for water getting behind the tile and running down the waterproofed CBU to the tub? ie: for a place for water to get out? I may be doing this same thing (ie: retiling a bath with tub) so I'd like to understand.

[cx]

Yes.

[wagsgt]

1. What is the thickness of the subflooring? What is the joist spacing?
3/4" OSB, 2x10, 13ft span
I would not tile over water damaged OSB without at least the second layer of plywood.

2. There is no advantage to caulking between wallboard and tub and some disadvantage. If you're using a sheet-type direct bonded waterproofing membrane and can attach it to the tub's tiling flange with Kerdi Fix or similar pookey, that's fine over an open gap there.

I am not in favor of the flexible sealant (or caulking) between tub and tile, but that's the current tile industry standard. I would want at least some weep holes in the sealant if that's the way the joints were to be filled.

3. You could do that and bond the membrane to the tub in that narrow area. Won't be a guaranteed fix, but it might certainly help. You would need something to bond the Kerdi to on the subfloor, thouigh.
Attach to the Ditra?

4. The maximum notch allowed depends upon the joist size and location within the joist span. We know neither.
3/4" OSB, 2x10, 13ft span

5. Not sure I understand the question. What size is the tub? Where does it fit in this opening?Tub goes against back wall where insulation is. Previous tub was 60x30, trying to add 60x32. Stud to stud measures 60 1/2" length. So If I push tub against plumbing wall there is a 1/2" gap at back

6. Hopefully you would make the transition somewhere outside the wet area and treat that joint as a drywall joint. So just take the CBU out further than tile would be and use regular drywall tape and mud, skim coat over cbu for smoothness?

[Tiger Mountain Tile Inc]

2. You'll get a variey of opinions about this. Being a pro I would get complaint after complaint if I did anything but silicone this joint completely. There's an argument to be made for leaving it without caulk or leaving weep holes but for me it just looks funny and unfinished. I say caulk the whole perimeter but it's your bathroom and you can do as you please.

3. I don't know why you can't just run a bead of silicone or even urethane between the Ditra and the tub? Trying to attach Kerdi seems a little more trouble than it's worth.

5. I think the shims on the tub are fine. The wallboard should cover any gaps if you split it 1/4 inch on each side.

6. Make the transition behind the tile. If you put in a 32 inch tub you'll probably have a leg that comes out past the tub- say at 35 inches. Run the tile backer out to 32 and transition to drywall at that point. Tape the seam with thinset and the tile will cover the seam and attach to drywall for the last 3 inches. Hopefully I've explained that ok.

[cx]

Originally Posted by CX

1. What is the thickness of the subflooring? What is the joist spacing?

Originally Posted by CX

4. The maximum notch allowed depends upon the joist size and location within the joist span.

[wagsgt]

Sorry cx, spacing is 16"OC. The current notch is top of the joist about 2 ft from exterior wall. If I went with 32 inch tub I would notch away towards center of house. That what ya need?

[cx]

You'll almost certainly exceed the recommended notching limits with that plan, but we know you're fixin' to do it anyway and it'll probably be OK. See my warranty information below.

Here's a good online reference for notching and boring of structural members in wood framing.

My opinion; worth price charged.

[wagsgt]

cx, Im not set on 32" if its advised against Ill stick with 30" but I will read attachment now.
Also regarding floor seems its ok to leave whats there if I add a second layer and ditra?

Tiger- Im not sure Im 100% following? The tub width is either gonna be 30" or 32" alcove tub. I think the leg part has me confused?

[cx]

I think I'd be comfortable with that.

[Tiger Mountain Tile Inc]

Originally Posted by wagsgt

Im not sure Im 100% following? The tub width is either gonna be 30" or 32" alcove tub. I think the leg part has me confused?

Here's what I'm talking about:

[wagsgt]

That makes sense, thanks for the pic. "leg" was what was confusing me, basically where the bullnose tile would go right?

Another question we are gonna add a recessed light in shower in addition to flush mount light and vanity. Right now there are 2 switches, one for fan and one for vanity/flush. I would like to add a 3rd switch for the shower light and have shower light and vanity/flushmount on dimmers, but as you can see in pic I dont have room for a 3 gang box. Would someone explain the reason for the double studs here? This is on the second floor and roof is trusses.

[Steve in Denver]

Would duplex switch work for you?