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Old 08-29-04, 08:02 PM
lostit
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I am in the process of repairing the ceramic walls around my bathtub. I have never worked with ceramic tile before, so I need any advice on how to get started. The prep work is complete, I have 1/4" plywood, a vapor barrier, and 1/2" cement board in place. I am ready to install the tile. I have studied books and have spent many hours researching this project, but am still a little apprehensive about the tile. Any pointers would be appreciate
 
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Old 08-29-04, 11:10 PM
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I'm confused about the 1/4" plywood. So you hung 1/4" plywood over the studs before putting your vapor barrier up and your 1/2" tile backer? Why?

Typically, even for a wet area you only need a 6 mil vapor barrier over the studs and your 1/2" tile backer over that. I guess I don't understand the need for the 1/4" plywood. Also, probably not a good idea to have a vapor barrier sandwiched between plywood and tile backer. The plywood will absorb the moisture and may force the wall to swell or sweat. There's no where for the moisture to go. If that moisture ends up between your tile backer and tile you'll start loosing your grout and your tile over time. The vapor barrier should be either hung from the studs, or you can use a roll-on membrane over your tile backer like Pro Red before you apply your adhesive and set your tile.
 
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Old 08-30-04, 02:10 PM
lostit
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I am new to tiling. The books I have read and everyone I spoke with told me to hang the plywood, put the vapor barrier and then the cement board.

So now you are saying, put the vapor barrier and then the cement board. Sounds like I wasted lots of time, money and effort.

So now I am totally confused.
 
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Old 08-31-04, 11:26 AM
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I double-checked with some fellow tilers, and they agree with me, but only in the context if this being a wet area. If you plan on this tile being constantly exposed to moisture then you have to reconsider. The problem is condensation. In your scenario there is nowhere for the moisture to go besides the plywood if this is going to be constantly wet. Over time the plywood will swell and fail the wall.

...but if this isn't a wet area you may be ok...but the fact that you're installing a vapor barrier tells me you are planning on this being a wet area.

Use your best judgement. You know what happens to plywood when it gets wet. Think about moisture getting locked in, and how it will affect your wall over time.
 
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Old 08-31-04, 01:44 PM
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Who told you to do this by the way? Professional tile setters? If so did they know it was going to be a wet area? What book did you say you saw this in?
 
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Old 08-31-04, 02:56 PM
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As Cobalt said, the vapor barrier is normally applied directly to the framing members, then the cement board. However, manufacturers of cultured stone recommend plywood over the studs before the vapor barrier. Possibly because the added weight of the stone (as compared to tile) could use the extra rigidity.

If the vapor barrier works correctly, there should be no condensation on the plywood, as the moisture is on the bathroom side of the barrier, not the plywood side.
 
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Old 08-31-04, 04:02 PM
lostit
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I greatly appreciate everyones advice and comments!

Yes, I talked to a several "Professionals". I told everyone I spoke with that I was replacing the existing bathtub surround. Also the book is Better Homes and Gardens, Tiling Projects.

I think my best move is to re-do what I have done and start again. I had rather spend a little additional now than have to replace this in a few years, or worse, have more problems than before!

Thanks again!
 
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Old 08-31-04, 09:25 PM
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Why re-do it? The plywood won't hurt anything, and provides extra rigidity for the tile (as well as shear strength for the wall, if you live near a fault). With the cement board or backer board over the vapor barrier, you are ready to start tiling. The plywood is no more susceptible to moisture than the studs would have been if the vapor barrier is correctly installed. Also, it wouldn't have been a bad idea to put in fiberglass insulation between the studs, even for interior walls.
 
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Old 09-01-04, 07:38 AM
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Except studs aren't made of several layers of wood bound with laminate that is that vulnerable to moisture. The way he has it now will result in condensation on the vapor barrier - on the inside AND outside depending on the temperature in the cold space in the wall behind the bathtub and in the bathroom. Over time that plywood will absorb moisture.

...now how much is really the question. If he was constructing a shower, and was preparing his walls for tile this way I'd definitely say he's in for a shocker in a couple of years. Since this is a tub surround it's not as critical, but he may be facing the same problem in the long run, but who knows. It's really up to him to decide if he wants to leave that plywood back there.
 
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Old 09-01-04, 11:29 AM
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Originally Posted by COBALT
Except studs aren't made of several layers of wood bound with laminate that is that vulnerable to moisture. The way he has it now will result in condensation on the vapor barrier - on the inside AND outside depending on the temperature in the cold space in the wall behind the bathtub and in the bathroom. Over time that plywood will absorb moisture.
But the moisture condensing on the plywood in this situation would have to originate from the space adjacent to the bathroom, not the damp bathroom itself. If the wall is an exterior wall, there is already housewrap, sheathing (plywood?), insulation, and another vapor barrier -- no problem there. If it's an interior wall, then the adjacent space is a cold, damp room. Scottish castle or basement? Which is why I recommend insulation, to keep the plywood the same temperature on both sides, not unlike a subfloor between a basement or crawl space and the bathroom.
 
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Old 09-01-04, 12:26 PM
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First, I hope you're not sheeting your house with plywood. I've seen a few houses where the do-it-yourselfer decided to use their scrap plywood under their siding, and then wonder later why their house is sprouting warts. Other materials are used to sheet houses. Not plywood, and for the exact same reasons.

House wrap and vapor barrier prevent large amounts of moisture, upsplash, and moist air from invading the vulnerable layers behind it over time - from the outside in. When working with a crawlspace it is recomended to hang mil plastic over the bottom of the floor joists to prevent moisture that is in the air from the cold air space from invading the subfloor -which I might add does include plywood, since the intent was not to have cold air moisture exposed to it. What you're doing by placing plywood on the other side of a vapor barrier on an interior wall is inviting condensation to form in between the plywood and the vapor barrier. Since plastic doesn't absorb moisture the only place for it to go is into the plywood, where otherwise it would either evaporate over time, or harmlessly go into the studs (virtually harmless - but structural members can take moisture a lot better than plywood).

Also remember that a bathroom with wet surfaces is an artificial environment. You're literally creating the condition where moisture will collect by exposing it to different temperatures. Moisture can also travel right through thinset, concrete board, and grout. To prevent underlayments like plywood from ever being exposed to moisture roll-on, fold-out, or other types of membranes are secured in place before the mortaring starts. That is not a vapor barrier. That is water proofing. A vapor barrier is not a water proof layer. Using a water proof membrane constitutes a different problem, but generally reserved for cases where a "wet area" is being constructed - a shower, or a floor that will constantly be exposed to moisture that is too much for a simple tile floor with basic tile and grout sealer.

I'm suggesting that a tub surround is in between a wet area and a tiled floor that is not exposed to water. Farther up the surround there probably won't be much moisture passing through, but down below where the tub surround meets the tub is where most of the damage will occur, and it will happen - especially if you don't protect it with a water proofing area, and stay away from using plywood underlayment.
 
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Old 09-05-04, 07:48 AM
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Originally Posted by COBALT
First, I hope you're not sheeting your house with plywood. I've seen a few houses where the do-it-yourselfer decided to use their scrap plywood under their siding, and then wonder later why their house is sprouting warts. Other materials are used to sheet houses. Not plywood, and for the exact same reasons.
Of course, there are plenty of alternatives to plywood as a sheathing product, but out here in earthquake country it's preferred over most others (such as OSB) by far because of its excellent shear load qualities and ease of use. But it's cost, not warts, that's causing us to look at alternatives. As far as condensation vulnerability goes, the same principles apply to floors as to walls and as to roofs. Know your layers.
 
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