taping and mudding corners in a shower??

[minnesotahusker]

I'm starting the taping and mudding process in my bath and have the joints to do where the duroc and sheetrock come together, namely on the ceiling and wall joints. Does a guy mud that with inside corner bead just the same as having drywall butting up on a regular wall? Or is there another type of mud that needs to be applied?

[Warner's Point]

I am a tile setter not a sheet rocker but I will tell you what I see on the job site. When we get on a job the taping and mudding is already done before the durock is installed. If the ceiling doesn't get tile then the Taper finishes it off like any other ceiling and the durock just butts to the ceiling and doesn't get taped. As for the walls meeting the durock we apply fiberglass mesh tape on the joint and then float it with thinset. This joint should be about centerd in the curb and be covered by tile anyways.

[minnesotahusker]

So the joints where the ceiling and the wall meet (sheetrock and duroc) do not get taped, they just have tile run all the way to the ceiling. The rest of the joints, either between the duroc itself or the duroc/sheetrock on vertical joints gets a piece of mesh tape and thinset to tape those joints. What about screw heads on the duroc, just one pass with the thinset and wipe smooth?

[reddog]

Do you have a membrane behind the dura rock that drains to the shower drain membrane?

[Warner's Point]

The screw heads on the durock don't need to be skimmed since they will be filled with thinset when the walls get tiled.

[minnesotahusker]

There is the moisture barrier behind the back wall of duroc, but I will end up putting some other type of barrier over the duroc, just for peace of mind. I would imagine I might be better off calling a local tile shop and seeing what they recommend as well. Warner's Point has helped ease myself quite a bit though.

[Tom7227]

When I did my shower tile I got a dvd from the Tile Shop and it helped a lot figuring things out.

[311Hemi]

Make sure you get the right kind of mesh, the grey stuff is what you should use.

Also, what is the moisture barrier you already have in? Typically you do not put a moisture barrier on both sides of the wall as this can create a moisture sandwich.

I used Redgard (home depot) for a moisture barrier on the baths I did in my new house and was happy with it.

In our baths we only ran the durock 7' or so up the wall, the upper 2' was drywall. Ran tile to the ceiling in one, and a couple inches higher that the durock in the other.

[minnesotahusker]

The moisture barrier that is there is due to the 'back wall' being an exterior wall. I ran duroc all the way to the ceiling because we will run tile all the way to the ceiling. I will put a type of moisture barrier over the duroc if needed, otherwise I will just tape and mud the joints and tile over the duroc.

My main concern was if I needed to put in interior corners where the ceiling meets the vertical wall in the shower part itself, or do I just run the tile all the way to the ceiling, which I believe was already answer, which makes sense. I do need to get the correct tape though, but I'm still a bit out from actually getting to the project. Just getting all my ducks in a row first.....

[frazwood]

I am not a contractor, but I have done a couple of tiled showers. Here are my thoughts:

1. I have used cementboard only on the walls. You definitely want to tile beyond the cementboard-drywall transition so that it is hidden. In theory, this cementboard-only approach should be "OK" since cementboard is tough and mold cannot grow on it. But, it is not waterproof, which is different. In this bathroom, I have a really good access panel and I have not had any noticeable leaks after 3 years of weekend use (it's at our lake cabin).

2. I have used cementboard on the walls covered by a water-proofing membrane about 2/3 of the way up the wall. As someone stated above, if you are doing this on an exterior wall with a vapor barrier on the other side... you have to be careful to not make a moisture sandwich. I didn't really like this method because the manufacturer of the waterproofing membrane insisted that unmodified thinset was required for putting the tiles on the wall. This means that the adhesion strength of the thinset was way less than with modified thinset. I would have worried that tiles would come loose eventually, but it's not my problem any more as we sold that house last year.

3. I am currently doing a bathroom (in our new home) and I decided to take an in-between approach. The same company that sells the waterproofing membrane also sells that material in bands for waterproofing the corners. In most cases, the leaks in a shower occur in the corners, so I used this waterproofing band to make sure that the corners are watertight and then tiled directly onto the cementboard elsewhere using modified thinset. I am still working on this project, so I have no idea if it is a good one long-term. My guess is that I'll be fine considering that approach#1 seems to have worked fine.

As far as the wall-ceiling transition, I have never bothered with it as long as I tiled to the ceiling... it cannot be seen and it looks fine.

Good luck.

[311Hemi]

The moisture barrier that is there is due to the 'back wall' being an exterior wall. I ran duroc all the way to the ceiling because we will run tile all the way to the ceiling. I will put a type of moisture barrier over the duroc if needed, otherwise I will just tape and mud the joints and tile over the duroc.

In that case you would have had a couple options. You could have used a 6ml poly on the remaining walls, making sure the plastic overlaps the pan membrane and then install the durock. You would want to make sure the outside wall overlaps the membrane as well. Since you already have durock up, I think your only option is to use something like RedGard or one of the other membranes (ditra might make one?). You would still mesh tape/thinset the joints prior to using RedGard.

If you use redgard (I liked this product!) many will say to slit the outside vapor barrier so you don't create a moisture sandwhich. I have the same setup you have with an outside wall, and I did not slit the outside wall membrane. Pretty sure my builder thought I was nuts when I even mentioned it to him. So, sandwich or not, I RedGarded everything. I had to use two coats, but pretty sure water isn't getting through it!

I assume you installed the durock over the PVC membane covering the shower base?

[delcecchi]

I was just thinking, it is not a moisture sandwich since any moisture can go sideways to escape, can it not? It is a limited area. Or do I have a flawed understanding?

[311Hemi]

I think by definition a sandwich is open on the sides!

Fairly certain that the experts in the area (which I am not) consider it a sandwich even though the sides are open (at least from my research when I was building a home last year). If moisture gets into the middle of the durock somehow, drying to the edges is probably a very very slow process...if it would even occur at all. Along with that if you do not resolve the reason for the moisture....that will only allow additional moisture to accumulate at a faster rate that drying.

Having one side open would allow more even drying to the whole sheet of durock. The "experts" would go as far as cutting slits in the poly on the exterior wall so it would dry to the outside. They would then put the moisture barrier on the inside.

[minnesotahusker]

311Hemi, there is the poly on the wall that runs floor to ceiling, nothing that overlaps the lip of the tub. The duroc is set up 1/8" off the lip of the tub, according to the manufacturer specs of that tub. I was planning on applying at least ditra in the corners and seams to make sure the major gaps are seals up and run the tile to roughly 1/4" off the top of the tub, then fill that edge with the appropriate colored silicone caulk. I'm going to talk to a few tile shops around the area and see what their guys do in order to get ready for a job. I'm leaning towards a whole ditra membrane over the duroc and just run it to a 1/2" off the tub to make sure that any water that does get behind the tile doesn't have a chance to get behind that lip on the tub and start the mildew issues.

As far as a moisture sandwich goes, I've always been puzzled by that if you have each end of the duroc open, the moisture has a way to get out. It is a lower level bath and it won't be used all that often until the kids get a bit older and are kicked down to the basement.