View Full Version : possible to dry behind shower tiles?

07-25-2010, 07:48 PM
Hi, I would really appreciate some advice. I'm a new home owner (1 year) and pretty new to this!

A few weeks ago, I realized that the shower tiles on the window sill (in the shower) were separating from those on the wall below them. They were probably slowly separating, but I wasn't clued in to looking for that sort of thing.

So, today I decided I'd check out what's behind the tiles before just caulking over the crack. I pulled a tile off and found it was pretty damp behind it. The tile came off with the adhesive attached to a layer of what looks like paper, green near the tile and cardboard-colored on top (wall side). The paper ripped off the wall board, which is pinkish if that means anything.

So I pulled the whole line of tiles off vertically between the removed tile and the tub. The paper was damp all the way down, wetter at the top near the window I think (where the obvious cracks are). The wallboard seems fine (not soft, not especially damp if at all), but now the paper covering is pulled off it where I removed the tiles, and the paper behind a lot more tiles is certainly damp.

My question is, can I just let it dry out for a while, then replace the tiles and grout/seal really well? If so, how long to let it dry? Or is it too late and I need to rip it all off and re-do?

Thank you, thank you!!

07-25-2010, 08:19 PM
What you seem to have there is tile on greenboard, which (at least in the latest national codes) is NOT allowed in wet areas. Keep in mind that tile and grout are NOT waterproof, and will allow some moisture through them, regardless of how well it is sealed. It is not the right way to seal things up around a window in a shower.

If the rest of the shower walls were built in the same way, you are likely to see those eventually fail in the same manner. If the house is actually new and not just new to you, you probably have a builder warranty. He should fix it as it is NOT done to industry standards.

National code requires an approved tile substrate in a wet area. Some brands of acceptable products are: Hardieboard and Durock. There are others, and any of them can work. Normally, you'd have a vapor barrier behind it. In a window area, that often isn't sufficient, and surface waterproofing is done.

A window, with it's horizontal surface (hopefully, it does have some slope into the shower) is a particularly hard place to waterproof.

If I had to fix this, and didn't want to tear the whole thing apart, I'd probably dig the greenboard out of there, then install some cbu (cement backer unit; i.e., durock, hardieboard, etc.), then liberally coat the surface with a surface waterproofing material (Redgard made by Custom Building Products is a good one - available at Home Depot and most tile stores), then thinset and tile. Lowes sells 1-pound boxes of thinset, rather than buying a 50-pound bag of the stuff (don't use mastic or anything premade in a bucket for the 'adhesive' - you want a cement product - thinset). If you need more than a couple boxes, then it may be cheaper to buy a full bag, even though you may throw away most of it. Once opened, thinset should be used or trashed if not used in a month or so. It will absorb moisture once opened, and cement will setup hard as a rock. Once that starts, it is useless, except as fill.

A good place for help on tile is www.johnbridge.com (http://www.johnbridge.com).

07-25-2010, 09:12 PM
It's kind of unavoidable...

It will only get uglier....

07-26-2010, 06:24 AM
quote; Keep in mind that tile and grout are NOT waterproof, and will allow some moisture through them, regardless of how well it is sealed.

I have been in thousands of homes with tile/grout walls, and they DO NOT have moisture behind them, unless the grout is cracked or the tile was not installed correctly. IF moisture gets behind the tile, it WILL come loose.

07-26-2010, 06:49 AM
Of course the immediate area will dry out if left exposed. The issue what is behind the REST of the shower tiles, and even more important...what is already behind those wet tiles at the window? Mold? Dry rot?

In all good conscience, my best and only recommendation is that the entire shower should be redone. It is true that many showers were built this way, and some survived with no damage. In my admittedly limited experience, compared to wheelchair or hj, I have always found SOME water problems behind when redoing one. If you are in a budget and time pinch right now, remove the immediately damaged and wet tile and board around the window. I would consider removing the wet drywall so a blower or fan could be used to make sure the insides dry out. Then patch it in.
I don't know how they feel about patches, but there is an exvellent tile forum we refer folks to: http://www.johnbridge.com/ (http://www.johnbridge.com/)

Windows in a shower are a bad idea, and of course it wasn't your idea to build it that way! Today, if redoing the whole thing, plastic composites are used instead of wood.

07-26-2010, 09:01 AM
Jimbo got the tile information link wrong...


07-26-2010, 12:49 PM
In a 'normal' situation, water will run off the tile and grout (walls, especially). But, some will be absorbed by the grout and some tile (porcelain is considered one of the most impervious next to glass, but still absorbs some moisture). On a vertical surface, unless submerged or water can pool, it does not penetrate much (if at all), and generally can easily dry out (especially in the desert areas like Phoenix!). But, those of us that live in areas where the humidity often reaches the 90% range or higher, things often don't dry out! Stick most any glazed tile in a bucket overnight and compare to a dry one. You'll see it has absorbed moisture. Grout will as well. Put that up against drywall or greenboard, and eventually, you'll have enough moisture wicking in to support mold and rot. A well-used shower over time may not get a chance to dry out, and the problem becomes bigger the longer it is used.

Precautions to prolong its viability are: use your towel to mop up any standing water or drops on the tile, and run the vent fan for awhile after to remove as much water vapor as you can.

When building a shower, the goal is to keep the moisture penetration to the minimum, and use products that aren't affected by moisture. Thus, tile, cement (as in grout or thinset), and cement backer board (cbu). None of them will decompose in moisture, but they can and will wick moisture to a degree. So, on the walls of a shower, you should either have a vapor barrier behind the cbu, and on the floor, there is a waterproof liner (or a tub, as in a tub/shower). There are also techniques that make use of a surface waterproofing, either a membrane in sheets, or a liquid painted on. These help limit how much moisture can penetrate into the wall structure.

A windowsill is a hard thing to make long-lasting in a shower. It needs special precautions and contruction techniques, as it can get hit with a fair amount of water, and if not sloped, it can pool. If not sealed well, it can leak or wick underneath at the window/tile joint. Grout sealer only slows moisture penetration and its primary purpose is to resist staining and make it easier to clean up; not to stop moisture penetration. If the window is not vinal or some other material that can withstand moisture, the paint on it needs to be perfect, which is tough as seasons change and things expand and contract. Rot is not uncommon in poorly constructed showers, and greenboard is a sign of improper contstruction, especially in new construction where codes have recognized that fact.

Many showers were built on drywall/greenboard and have survived. Many have hidden rot. Many have fallen apart. Depends on where you live, how much it is used, and the original materials and detailing. On many, you wouldn't notice problems until you tore it apart for remodeling or repair of something else. Often, most of it might be perfectly intact (the plumbing end often doesn't get much spray), but the sidewalls and back might get hit by the shower nearly constantly during use - those are often the first to go. It's usually the lower 1/3 as well, as up higher, it doesn't get as much spray. The tub/tile junction at the back of the shower is probably the worst. If the tub is not level so that it is designed to drain into it, water can pool, and make things worse fast. Lots of ways to get it wrong.

The Tile Council of North America (TCNA) has numerous approved techniques on how to build a shower and tub/shower. Greenboard is in NONE of them (unless an approved surface membrane is applied, and then, regular drywall is the manufacturer's recommended substrate, not greenboard). Most building codes refer back to this.

07-29-2010, 09:25 AM
Thanks everyone for the education. I've been learning a lot through this an other blogs.

I still have one lingering naive question. I am re-doing several aspects of the house which are outside (deck, windows, garage) so need to be done in summer. So, I really want to patch the shower tiles and worry about it later.

My naive question is, what's the worst that can happen? If it continues to slowly get wet and it rots out behind the shower to the point of having to replace the whole thing, is that substantially more work than replacing it all now? Is it likely that the rot would extend to more serious structural parts, is that the problem? I just need a few months delay, but of course the risk would be that I decide that it's fine later and don't get to the full replacement...

Thanks again!

07-29-2010, 10:31 AM
:(Moved into our house about 2 yrs ago, originally built in 2000. There is green board behind 4 1/4" tiles. We have a window in the tub.shower also. We are in the middle of gutting the whole thing and putting in all new everything. at the window sill the leaking water has caused a small amount of mold on the studs, insulation, behind the greenboard. The OSB sheathing has shown signs of rot/swelling as well. Will have to replace some minor wood framing as well.

We'll be using hardie backer around the tub as well as the window returns, then apply some kerdi. The window surround will be solid pieces of 3/4" granite slabs with the sill sloped.

You'd think a house built in 2000 would be better built.....:(

07-29-2010, 11:22 AM
If you want to wait, and don't care about looks, take some plastic and tape it to the window and sides, and lap it into the tub's vertical wall a ways. This will cause it to drain into the tub. Then, think about it. An advantage to this is that if there is moisture underneath, you'd see it likely condense on the back side of the plastic.

A window in a shower is a tough (but could be nice) thing, since they are hard to waterproof. Greenboard never was a agood idea.