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Unread 05-17-2008, 10:08 AM   #1
HDmstng
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Tile backer meeting lip of tub question

I just installed a new 5' tub and am in process of attaching the tile backer. The lip of the tub is only offset by ~1/4" from the studs. When I attach the 1/2" Densshield it will overhand the lip of the tub by ~1/4" (a little farther in some places and less in others) instead of being flush with the lip.

1) Is this going to be an issue when I go to tile?

2) Will good silicone caulking do the job? My plan would be to put a bead between the lip and the back of the Densshield.

3) After I tiled (leaving a 1/8" gap between the tile and the bottom of the tub) put another bead of silicone caulk in the new gap that has formed between the tile going past the Densshield and the lip of the tub.

4) In question #3, do I leave enough space for grout to go into that bottom area (between the tub and tile), or just fill it all in with caulking?

5) I do have a question on Densshield as well. The manufacturer recommends the use of 5/8" thick for walls with studs that are 24" OC and 1/2" for studs that are 16" OC. Is the extra 1/8" thickness for strength, ie not falling off due to the weight of the thin set and tile or is it to protect from flexing with the extra 8" between studs, or both? I have 24" OC metal studs along the 5' wall section, but since it is a firewall (I'm in a condo and it's between my neighbors), there are two layers of 1/2 drywall already there, so flexing shouldn't be a problem. The wall is solid. So if the extra 1/8" of thickness is to prevent flexing, can I go ahead and put up the 1/2" instead? It'll help with minimizing the gap I've discussed above.


Thanks in advance for your help!
HD
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Unread 05-17-2008, 02:55 PM   #2
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Hi HD

The denshield overhanging the tub lip is a good thing. No problem there.
Leave grout out of the joint where the tile meets tub. Silicone between
tub and denshield. Caulk between tile and tub as well. If you have two
layers of sheetrock on the 5' wall I would imagine 1/2" would be fine, but
that would be a question better answered by their tech department.
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Unread 06-20-2008, 12:09 PM   #3
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HD's Bathroom Remodel

I have a 5 foot wide by 10 foot long master bathroom I'm remodeling. There is a 5' tub, toilet, and 5' vanity. I'm still trying to decide on tile, size, color, etc..., but have that narrowed down somewhat.

Here are links to a couple of questions already posted. Seems like it's best to keep it in one thread.

http://www.johnbridge.com/vbulletin/...ad.php?t=62816

http://www.johnbridge.com/vbulletin/...ad.php?t=57624

I used 1/2" Densshield up against two 1/2 pieces of drywall at 24" OC. The extra drywall is a firewall. Used a little bit thin set between the dennshield and the drywall to help secure it to the wall. There was about 1 foot from the right side edge that didn't have a stud to drive into it. Ended up putting a few screws in though to help secure it.

First question is in regards to repairing the densshield. There is a zoomed in picture that shows the corner paper torn off. How should I repair that? Will the thin set and tape for the seam fix it? Or do I need to cut it out.

Second question is about some of the screw holes. One went in too far and I completely backed it out, how do I fix that hole and others that went in a bit too far? 100% silicone, thin set, red gard?
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Unread 06-20-2008, 12:34 PM   #4
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After the walls, there is also the matter of the subfloor. I plan on using 1/2" cement backer board over the 5/8" subfloor. Around the toilet I replaced the wood, with current 5/8" plywood, but it's not quite 5/8" so there is a bit of a gap. The new piece sits a tad lower than the existing subfloor. And there is some deflection in one area when I step on it. See the pic below.

The cement backer board is 3' x 5', which fits perfect for the 5' wide bathroom. I plan on resting it on the part of the old subfloor to the left and making sure I have enough thinset in the new lower area to ward off any deflection. The 4th picture has the cement board in green, and the grey is the thin set.

Since the toilet is going to be sitting on this area, will it be strong enough with the 3' x 5' x 1/2" cement board to spread the force out?

Also, how big of a cutout should be left for the toilet flange? The pipe extends up an extra few inches so it can be cut to the right height once the subfloor/backerboard/tile is set.

Thanks again for all the help!
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Unread 06-20-2008, 01:13 PM   #5
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Can't help with the Denshield questions.

The subfloor must not be flexing before you put down the backerboard. Backerboard has not real strength of is own, so you can't count on it fixing a bad subfloor. 5/8" subfloor is the minimum acceptable, but it has to be just about perfect for a long lasting tile installation. You have a patch that looks like it spans only one joist bay, and it's got unsupported edges, too. The unsupported edges need to be supported by solid blocking. I'd also like to see another 1/2" layer on top of what you've got. You can then use 1/4" backerboard or a membrane as your underlayment.

The drain should rest on top of the finished floor (tile). You don't need to leave much gap around the pipe, but you do need to allow for some clearance, say about 1/4".
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Unread 06-20-2008, 01:31 PM   #6
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Quote:
Can't help with the Denshield questions. The subfloor must not be flexing before you put down the backerboard. Backerboard has not real strength of is own, so you can't count on it fixing a bad subfloor. 5/8" subfloor is the minimum acceptable, but it has to be just about perfect for a long lasting tile installation. You have a patch that looks like it spans only one joist bay, and it's got unsupported edges, too. The unsupported edges need to be supported by solid blocking. I'd also like to see another 1/2" layer on top of what you've got. You can then use 1/4" backerboard or a membrane as your underlayment. The drain should rest on top of the finished floor (tile). You don't need to leave much gap around the pipe, but you do need to allow for some clearance, say about 1/4".
Thanks for the quick reply Bob!

The patch goes under the tub and is attached via a sister joist, it then rests on a single joist, and is once again attached to a sister joist at the other end. (see the parallel black lines at the bottom of picture 1) The only unsupported edges are perpendicular to the joists along the patch.

Should those have been boxed in prior to the patch along with the sister joists? Is that what you mean by solid blocking?

I'm in a bit of a pickle now if I have to remove the tub and redo the patch. Any other ways to shore up the area?
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Unread 06-20-2008, 02:49 PM   #7
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So it sounds like you cannot add bracing from below. You need to add extra bracing for that soft spot of the patch. Personally I'd add bracing all around, just takes time and a few boards to brace it up.
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Unread 06-22-2008, 06:38 AM   #8
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I would pull up that piece of wood by the toilet where it flexes and put some blocking in there. You do not want anything to flex over there especially when you put down a toilet. Get a 2x4, measure the distance between the joists and puts the 2x4 blocks in there. Screw those blocks in there and then put the board back on top. It shouldn't flex from there. I had the same problem but put about 2-3 pieces of blocking. Just remember, its not like sheetrock where you can cut out the piece and do it again with spackle. Once the durock goes down with the thinset, screws, thinset and tile, you're really screwed. If you have access below, then you can always make an emergency repair.


good luck and keep us posted.

**just took another look. How come you don't have any screws holding down the plywood on the right side of the flange into the joists? put some screws in there and see if you have any flex.
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Unread 06-22-2008, 10:11 AM   #9
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I really have to say I'm disappointed with the reply's in that you aren't telling me what I want to hear..."once you thinset the 1/2 cbu over the flexing part and screw it down, you won't have a problem." If the tub wasn't already in place, this would be so much easier to take out the patch, box it in with some additional 2x4's and be done with it. Long story short, I rushed because the plumber was here and we were going to set the tub and it was the last thing in a long day. Live and learn!

All is not lost though.

In Pic #1, the black and red lines are the joist. The uppermost joist (in black) and patch extend under the tub, hence I'd have to remove the tub to box properly. Since the densshield is up and the tub is secured, it's on to plan B. What is fortunate is the blue lines represent the main beam of this second floor bathroom. I believe there are two 2x12's that support the joists which means I might have enough space to get underneath and add some additional support(maybe). The joists in red are offset from the ones in black to continue the span across the second floor.

I'll cut out the patch (not under the tub) and subfloor between joists 2 and 3, all the way to the main beam. (See Pic #2). There is a bedroom closet on the other side of the wall on the left, so I can pull back the carpet and cut out an opening for access. A secondary joist that will rest between Joist 1 and 2. See Pic #3, the blue line, can the be slid in. The joist will sit on a 2x4 (or 2x6) that is sistered to the main support (See pic #3, the blue line labeled 2). On the left hand side under the closet is a sill plate that the new joist can rest on. It'll only be a span of about 4-5 feet total.

The newly cut out patch will then be properly boxed in with 2 x 4's (or should it be 2 x 6's) all the way around! After that, a little thinset and the CBU should be able to go right on top???
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Last edited by HDmstng; 06-22-2008 at 10:19 AM.
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Unread 06-22-2008, 01:14 PM   #10
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That sounds like a plan, H.D. I'm thinking there won't be a lot of traffic behind the toilet.
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Unread 06-22-2008, 08:21 PM   #11
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sounds like you got a plan there HD. Let us know how you make out.
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Unread 06-23-2008, 01:24 AM   #12
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Some thoughts on the Denshield minor damage.

I have been tiling a roon full of Denshield. Where I have empty screw holes, I have filled them with 100% silicone. Same goes for any or all over countersunk screws. Just a dab of silicone to seal any breach of denshield coating layer.

If coating laminate is loose at corners ( not binding, I have lifted a tad and put a little silicone between the rock and outter grey layer. then pressed closed.

For the seams between the sheets, fill in with the silicone and let dry before taping with ( CBU Mesh tape) not the drywall mesh tape. After silicone drys you can ruff it up with some 80 grit sand paper.

The exposed corner void of the grey coating - dust off then smear a good coating of the silicone into and over all exposed rock. Let dry , Then ruff surface without breaking through to rock. You wanna maintain a water proof layer over the rock.

Silicone ( fill in ) all joints and gaps at all denshield meeting points including inside and outside corners. Keep the seams clean and smooth and at a minimal width.

I have been using GE Silicone II XST Paintable Formula White. Thinking best adhesion with thinset using the paintable version.

After taping over all seams, and dabing screw holes, viods etc with silicone, I have had very good Adhesion and bonding with Latacrete 254.

No issues so far.

Good luck with your project !
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Unread 06-23-2008, 07:39 PM   #13
HDmstng
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First off, thanks Crater for the tips on the densshield! I ended up just cutting that piece out and patching it with a nice piece of densshield. The silicone sounds like it'll do the trick for the rest of the areas.

One tip I have on installing the Densshield. I set the clutch on my drill so that it would stop just before the screw went all the way through the densshield. It worked for most screws, although a few did make it through farther than I'd have liked. An even lower clutch setting would probably work.

--------------------------------

Now shoring up the subfloor. After pondering for a while, there was additional access to the floor.

This is in the closet of the bedroom next to the bathroom. I had already cut out access for the plumber to get to the tub drain. Just had to expand over to the next joist for access to the flexing point. A 2x4 was slipped in to slide the 2x10 over the span and onto the main beam, ~52 inches. The 2x10x54 inches was lighter than I thought it would be, but the 2x4 slide did keep it from hitting the plumbing lines, etc...

The next picture is one into "The Void". You can see the 2x4 resting on the main beam that the 2x10 would rest on.
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Unread 06-23-2008, 07:50 PM   #14
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The span was only 52 inches, but the 2x10 was cut to 54 inches. I notched a 3.75" by 20" section out of one end of the joist and then tapered the end that was going to rest on the main beam. The notched part and the taper allowed for the beam to be twisted up into place. In addition, if the need ever arose to work on the plumbing, the notch would allow for some access.
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Last edited by HDmstng; 06-23-2008 at 08:02 PM.
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Unread 06-23-2008, 07:58 PM   #15
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After wrangling the joist into place, it was hammered forward. A couple of 2x4 blocks were screwed into place underneath the joist and some shims were used to jack it up against the subfloor. I did have very limited access from below, and in the second picture you can see the new joist resting on the beam.

Back in the bathroom I screwed the subfloor down to the new joist, and no more flexing at the patch!
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