Q. Several years ago, we had a local guy redo our bathroom and shower area. Last year, I noticed that there was some discoloration on the drywall outside around the curb (meaning the threshold, a built-up sill entrance) of the shower entrance. This spring, a couple of tiles came loose, and we noticed that it was damp under the tile. We contacted our contractor, and he came and removed some of the tile, patched the wall and laid tile back. The grout was touched up and everything looked fine. Now I see discoloration again on the drywall. Should I expect the same fix again or is there something more going on? — Lori in Noble County

A. Showers are not easy, and if there is anything I’ve learned in working on and installing showers for 30-plus years is that we learn something new with every install.

First, today’s walk-in showers have more features like niches, cubbies and seats, and all of these have corners. All corners are susceptible to leakage regardless if they are inside or outside corners and most of these features typically have a somewhat flat area like the seats.

Curbs and entrances are always vulnerable and must be properly waterproofed before tile is installed over them. Most problems we see are with flat areas, such as half-walls and benches including the curb; these are especially difficult to get to drain water into the shower.

Keep in mind that tile and grout are designed to take the bulk of the water away, but they are still porous, and water gets behind the tile and will destroy a wall and subsurface if it is not waterproofed.

Flashing tape must be used around all these vulnerable areas if they are to stay protected from rot. We use a secondary drain system which channels the water and moisture that penetrates the tile to the drain, and the subsurface is protected by waterproofing.

We also have been using vinyl corner bead and trim for the waterproof drywall and using aluminum screws and nails, so they won’t rust and cause unsightly discoloration to the exposed wall.

Jeff Deahl is past president of the Builders Association of Northeast Indiana. Questions for the Square Corners column may be submitted at ba-ni.com or email info@ba-ni.com.

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