Ask the Architect

A leaking bathroom


Q. We built a new addition with a bathroom, and the shower leaked into our first floor. The plumber says he did everything correctly, but the walls, not the floor, are to blame. The tile has come loose, and the walls had to be covered with plastic until the contractor can figure this out. The plumber thinks they used regular or water-resistant, not waterproof, wallboards. What can you tell us about what to look for, since the walls and tile all have to be removed and we don’t want this to happen again?

A. Normally, showers are lined with concrete- or plaster-based fiberglass-reinforced wall panels specifically made for that purpose. If green paper-covered “green-board” was used, then it’s understandable why it didn’t last. Usually when I hear stories about the wrong board being used, it takes about a year, maybe two, before the tile grout develops enough openings to allow water through the tile joints, causing the tiles to start pulling away from the wall. I’ve been called more than once by readers to see the collapse of an entire wall of tile.

As bad as this problem seems, you’re lucky that it happened quickly enough for the parties involved to have come back to fix it. Often I hear that the contractor cites some time limit, like a one-year guarantee, and then refuses to come back. You’re also lucky that they’ll strip the walls to replace instead of just trying to fix a few tiles. Replacing a few tiles would never fix the underlying problem, and the tiles or grout rarely match the surrounding tiles.

The fact that this happened makes me question whether the person who installed the wrong board knows how to waterproof a shower, since just putting up the right wallboard is only part of the job. Manufacturers make products that are part of a system. Some training or study is required to understand how systems of waterproofing membranes are assembled. With most of the products, the sheets of fiberglass-reinforced membrane go together, like wallpapering a room or wrapping a gift. There’s a method to this, making certain the overlaps and amount of adhesive are thorough. But it’s still possible to get the system wrong.

If all the last installers did was apply tile adhesive to the wallboard, you had no redundancy of waterproofing, a true mistake. You need to discuss the system with the installer, before any new work takes place. They got it wrong once, so I’m unsure, as you should be, too, that they can correct it the right way. Without an architect to advise you, you’re going to have to know more than you did the first time. I know that people fear the cost of an architect. One reason I’ve written this column for 27 years is to inform people that they shouldn’t fear consulting a paid professional, and should understand that we save people money and aggravation.

© 2017 Monte Leeper. Readers are encouraged to send questions to, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.