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Unread 02-16-2003, 02:51 PM   #1
Registered User
Join Date: Feb 2003
Location: Austin, Texas
Posts: 12
The great, gory upstairs bathroom project

Here's the story so far:
I apolgize in advance for the length of the post and the fact that it covers more than tile work.
My house was built in 1975. The original recessed tub and shower surround were faux marble and have been removed. The tub has been replaced with a 60" long Americast unit. The faux marble will be replaced with 6" x 6" ceramic wall tile (Interceramic Palladio Crystallo is the plan).

The wife wanted a niche on the backwall to set soap, shampoo, etc. I wasn't a big fan of the idea but I built it because we've been married nearly 40 years and I've found accomdating her few wishes is a good life strategy. I built the box for the niche out of 3/4" plywood and it is sturdy (about 16" w x 24"h x 6"d inside dimensions). I've nailed this box to the backwall framing, sloped the bottom of the box so that it will drain water out. Behind the back wall of the surround area is an open space where HVAC duct work is located which is why the depth was available.

I put up 1/2" green sheetrock to replace the torn up 1/2" sheetrock that was behind the marble surround on both endwalls and the back wall. On the back wall the sheetrock runs down to the top of the turned up tub flange. On the endwalls the green sheet rock goes down to 1" above floor level. I fiberglassed the inside of the niche box and brought the cloth out and around over the green sheetrock for about an inch.

The distance between the end wall studs is 61-1/2" give or take, depending on where you measure. The end walls are not square with the back walls -- off from square about 3/8" at 3 feet out from the back wall. The 1/2" sheetrock on each endwall reduced the total distance between the end walls to about 60-1/2". This left about a 1/2" gap between the new tub and the end walls. Since the end walls were not square with the back wall, I shimmed the tub out from the back wall on one end so that the tub ends were approximately parallell to the green sheetrock on the endwalls. The result is about a 1/4" gap on each end wall from the tub and about a 3/8" gap between one end of the tub and the back wall. I caulked the gap between the tub and green sheetrock with a silicone caulk. I put up 15# felt paper on the green sheetrock behind where the backer board would go and let it hang down 1/2" below the upturned tub flange.

I installed 1/2" CBU(Hardiebacker) over the felt paper and sheetrock. Since there is still a gap between the tub and the sheetrock on the endwall, the CBU sits on the upturned flanges of the tub, but the outside surface of the CBU overhangs the tub flanges about 1/8' to 1/4". On the back wall the CBU sits on the upturned tub flange at the end where the tub is shimmed away from the wall. The bottom course of tiles can hang down below the upturned tub flange without interference all the way around. When I put up the CBU on one of the end walls I noticed for the first time that the wall was not flat. I ended up shimming behind the CBU with layers of felt paper until the CBU on that wall was flat.

I did a poor job of upgrading the framing so that I could not go straight in with the screws holding up the CBU at the inside wall corners. I ended up putting the CBU screws in at a 45 degree angle to catch the corner stud with the screws. I used #9 x 2-1/4" cement board screws since I was going through 1 inch of CBU and sheetrock. The corner screws have been seriously over driven to get the heads below the surface.

I generally had a lot of trouble driving the cement board screws because I could not get the heads flush with the surface before the screw bit would start spinning. Once I got the screw heads boogered up I would throw them away and try again. Wasted a lot of screws this way. I also went through a lot of #2 bits (Dewalt brand). I finally started drilling an 1/8" pilot holes and drilling a countersink in the surface of the CBU with the tip of a masonary bit. This made putting in the screws a lot easier, but I have ended up with screws below the surface by as much as an 1/8". I also have a few holes in the CBU where I thought there was a stud and have pulled out that screw. I think I've used the wrong screws because when I mounted the CBU to the back wall of the niche I used a shorter screw from a different manufacturer that said it was designed for use with Hardibacker. These screws had a head designed for a square drive bit and set perfectly with no problems.

Thus endth the confession of sins and now beginneth the plea for absolution and suggestions.

As I see it now, the big problem was not planning adequately, not understanding the materials, and trying to compensate in jackleg methods for the problems encountered along the way. I am disgusted with the sorry quality of work but I would like to know if there is anything salvageable besides the tub.

If I need to regroup I think what I should do to fix things is as follows:

1) Tear out sheetrock on backwall and endwalls.
2) Add studs at corner so backer board can be attached with screws driven perpendicular at corners.
3) Shim studs on back wall until flat and square with endwall that has plumbing.
3) Push tub up against endwall with plumbing to remove exiting gap.
4) Shim studs on opposite endwall to flatten wall, square wall and remove gap due to difference between end wall-to-end wall stud dimension and tub length dimension.
5) Reapply sheetrock and CBU.

Given that these steps are correct, and I of couse ask for thoughts on this, here are the current questions:

1) Is there a serious disadvange of mounting the tub sides against green sheetrock instead of directly against the studs? Mounting against the sheetrock means I have to build out the one endwall about 1/2" instead of 1-1/2", which seems like a lot. I would prefer not to have to push out the endwall with the plumbing because there is an existing door and built in linen closet on that wall.

2) Can the niche be made to work long term without leaking? If so what's the best way to handle it assuming that it will be covered with CBU with the inside joints pookied with an appropriate mortar and mesh tape.

3) I picked Hardibacker instead of the "common" CBU sold at HD because it looked easier to deal with for a DYI guy. I also notice that there is now a Hardibacker 500. Is this any better or worse? Should I be using the "regular" CBU instead of the Hardibacker?

Any help with all this would be appreciated. I want to do it right the second time.

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Unread 02-16-2003, 04:00 PM   #2
Tile Setter
Join Date: May 2001
Location: Austin, TX
Posts: 4,840
If I were you I would take out the Greenboard, get your framing squared away, then apply the felt paper over the studs. Follow this with the CBU . I use Hardibacker as well. I've noticed the hardibacker 500 is only stamped on the 1/2" stuff. This is what I use for walls as the 1/4" seems a bit flimsy for walls

Secure the CBU to the studs with galvanized roofing nails. The screws are a big problem as they eat up bits and do not countersink well.

As for the tub. It should be secured to the studs. If there is a small gap between the stud and the tub flange, you can use shims. Larger gaps should be addressed by adjustments in the framing. Since you have 1/2" gap, I would adjust the framing

The niche....well you can go back with the fiberglass as you did before OR you could use a roll on waterproofing membrane to seal it off before tiling. Glad you added the slope

Good..Fast..Cheap. Pick any 2...can't have all three
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