Replacing damaged tile surrounding tub/shower

Q.    The 4-inch square tiles on the back wall of my tub/shower in my 65-year-old house are about to fall off the plaster and lath wall, which you have probably guessed is also in bad shape.

Damaged tile
Tile starting to fall off

Which way should I go to repair this problem? Tear everything out to the studs, install plaster board or plywood (which kind?), apply a sealer (which kind?), and re-tile? Or should I go back to the original way–clean the area down to the lath, re-plaster (base and top coats), apply a sealer and re-tile? Sincere thanks for your help.

A.    The best way to go would be to remove everything to the studs and start over by applying backer board to them. Then install the tiles after cleaning them up or buying new tiles.

If this is an exterior wall, make sure that the insulation is in good shape, staple a 6-mil plastic vapor retarder to the studs, and fasten the backer board to them.

Polyurethane caulk needs to cure for a week

Q.  I know that you are a fan of polyurethane caulk for its performance, and I have used it for some time. I had a curious experience recently, and wonder if you might have any insight.

My shower stall was in need of some caulking, both inside and out. Unfortunately, several hours after I completed the job, my son used the shower. I noticed several days later that while the caulk on the outside of the shower stall retained its white color, the inside caulking, which had been exposed to running water, developed what appear to be small rust stains.

There is not an overabundance of them, but enough to be somewhat annoying. They have not changed or grown since I first noticed them, which has been about two weeks now. I can only assume that the water had a reaction with the caulk before it had sufficient time to cure. Are you familiar with this phenomenon?

A.    Polyurethane caulking needs to be allowed to cure without getting wet for seven days. Otherwise, it turns somewhat pink. Unfortunately, you will have to remove it (which is not easy to do) and put new caulking if you cannot live with the change.

Or try to apply a thin film of the same caulking over the stained one after making sure it is thoroughly dry, and be sure not to let it get wet for a week, if that is possible. Otherwise, choose a different brand such as DAP Kwik Seal Plus Premium Kitchen & Bath Adhesive Caulk w/MICROBAN, a mildew retarder.

I have used it as well to see how it would hold up, but was disappointed over time as it separated from the tiles. But it did remain sparkling white. It has some silicone in it, and my experiences with silicone products have not been too successful, which is why I prefer polyurethane caulking compounds.

Bathroom stays wet despite exhaust fan

Q.  Every time we take a shower, the walls just get very wet and sometimes the water runs down the walls. We have a very good ceiling fan. We are at our wits end, what could be causing this problem? Any advice would be greatly appreciated.

A.    Have you checked that the fan exhausts outside through a gable wall? And that the outlet is not blocked? If the fan exhausts in the attic itself, or through a soffit, gable or ridge vent, it is not doing its job and you should have that taken care of. Your family may also be taking some long or very hot showers; that will overwhelm the ability of the fan to keep up with the moisture generated by the showers.

Smell emanates from new bathroom sink

Q.    Last summer, we renovated our bathroom and had two new sinks installed as part of the work. Lately, there is an awful smell when using one of the sinks. The stopper and trap are both clean. Do you have any suggestions for eliminating the smell?

A.    If the two sinks are made of imitation marble or another plastic substance, it is possible that the chemicals in one of them is outgassing, but it would seem that this would have happened earlier.

Perhaps bacteria have developed in the overflow. Put fresh Clorox bleach in a spray bottle and spray it generously in the overflow opening. If that does not do it, take the stopper out and stuff a rag in the waste pipe to block the end of the overflow. Pour Clorox bleach in the overflow until it is filled and wait until it drains through the rag. Be sure to wear heavy-duty rubber gloves and dispose of the rag when done.

Recommended caulk for use in bathrooms

Q.  I would like your recommendation for a caulk for bathroom applications: shower enclosures, sinks, base of the toilet, etc. A few years ago, I used Phenoseal, because that is what a plumber used. I had previously used silicone caulk and found it difficult to apply cleanly.

The advantage of Phenoseal is that you can smooth it out with a damp finger (or similar shaped rod) to get a clean bead. If you make too much of a mess, you can clean it up with a wet sponge and start over. You can’t do that with silicone.

Now the downside: After a year or so, a slight amount of black mold started growing in the caulk, mainly in the shower enclosure (not surprising since it’s a wet environment). Note that I had bleached the area before applying the caulk, and I tried bleaching it when the mold first appeared. This helped some, but now 5 yrs later, the caulk in the shower enclosure is heavily overgrown with mold, and I need to replace it.

Should I still use Phenoseal, perhaps with an anti-mold additive? I assume that Phenoseal is susceptible to mold because it is a water-based (latex?) compound. Or should I switch back to a silicone caulk and practice, practice, practice laying down a clean bead?

A.    In my experience, silicone is the worst thing to use at the joint of a tub and tiles. I have seen so many failures in my nearly 60 years in the residential construction field. It will eventually peel and allow water to get behind it, leading to serious problems.

I have used polyurethane caulking for bathrooms for many years. But you need to allow the caulking seven days air-curing before you can get it wet or it will turn yellowish-pink. Even then, the white caulk will turn slightly greyer over time.

You can find polyurethane caulking in building supply houses that specialize in masonry and waterproofing products. A.H. Harris, with stores throughout the east coast, carries Sikaflex 1-a, my favorite and a product I have used for 50 plus years. Their website is

You may want to try Dap Kwik Seal Plus Premium Kitchen & Bath Adhesive Caulk with Microban. The manufacturer says that Microban fights mold and mildew and the growth of stains and odor-causing bacteria. Although it is a siliconized latex caulk, it has much better adhesion than pure silicone caulking. It is guaranteed crack-proof.

Unfortunately, although the caulk remained white, I have also experienced separation between tub and tiled walls in year-long tests on the same tub, half of which was caulked with it and half with Sikaflex-1a.

Painting old tile

Q.  My question is about a process I’ve recently seen advertised that seems to use a process of spraying on a coating, similar to the one used to re-finish old tubs, to paint old tile.

I live in a 1930s colonial with a pink and black tile bathroom that I hate. I can’t bring myself to justify tearing it out since the tile is otherwise in excellent shape and the cost of a full renovation is prohibitive. Are you familiar with this process? Do you know the effectiveness and cost?

A.    Painting ceramic tiles is always a somewhat risky business as their glaze is a challenge for any coating.

I am not familiar with the process you have seen advertised, and I think it would be quite expensive. An alternative that is bound to be a lot less costly is to prime the tiles with B-I-N and paint them with a gloss or semi-gloss alkyd top-quality paint. There are also some epoxy coatings that would be suitable.

But the success of any painting job, especially over glazed ceramic tiles, is in a thorough clean-up and preparation. Tiles that are over 70 years old have an accumulation of grime embedded by steam that has to be removed. It is also helpful to abrade the tiles slightly with medium sandpaper and an orbital sander. Be aware of the fact that any scratch in the final coating may start the process of peeling as steam gets behind the coating.

Best way to vent a bathroom fan

Q.    I am installing a bathroom fan. Can I take the exhaust vent (the 4-inch diameter hose) and run it up to my ridge vent which runs the length of my ranch house? My wife does not want me to cut a hole in the side of my house. What do you think of a light in the fan?

A.    You should never vent a bathroom, kitchen or dryer vent into a ridge, gable or soffit vent — and in all but the hottest climates, never vent through the roof either.

These vents should exhaust through a gable wall. Venting these appliances through a ridge vent causes two problems: Condensation in the surrounding area that will stain and damage the roof sheathing, and wet the insulation as it drips on it;  and cause the condensate inside the vent to run down the vent and damage the ceiling, the fan and its housing (also the case when venting through the roof).

In the case of a kitchen vent, grease can also present a fire hazard. Venting through a soffit — an intake — simply takes the moisture back into the attic where you don’t want it.

It is best to vent bathroom fans by means of a bell-end, solid, schedule 20 plastic drain pipe. The bell-end should face toward the fan. Lay it with a slight pitch to the outside on top of the attic floor joists and snuggle 4-inch thick fiberglass batts against its sides and top. Dryer and kitchen vents should be metal and dealt with in the same way. A light/fan combination is your choice.

Re-surfacing a bathtub

Q.    The surface glazing of my bathtub is mostly gone. I do not want to replace the tub at this time and would like to refinish it until such time as we remodel the bathroom. Apparently, there are several different professional refinishing systems available (acrylic, 2-parts epoxy, etc.) Which system is best in terms of durability, resistance to discoloration and chipping, etc?

A.    Bath Fitter installs acrylic tub and wall liners directly over your existing tub — and walls if you choose the entire package. They claim a very long life expectancy of 25 to 30 years. Perma-Glaze is a different process that is applied over chips or the entire surface of tubs and sinks. Of the two, my personal feeling is that the acrylic liners may be more durable.

Be aware that neither of these systems will give you as hard a glaze as the original, so do not use harsh cleaning compounds on it.