Showers can be a beautiful part of the bathroom, especially when tile is part of the finished product. But the beauty will not be long-lasting if the standards and best practices for tile installation are not followed.
Although the Introduction section of the ANSI document is not a part of the A108 installation standard, it defines a wet area in section 2:18 as “tile surfaces that are either soaked, saturated or subjected to moisture or liquids (usually water) such as in gang showers, tub enclosures, showers, laundries, saunas, steam rooms, swimming pools or exterior areas.” This means that the shower is considered a “wet” area.
According to the ANSI standard A108.01-3.6.4, “all horizontal ledges/rims shall have a slope such that any fluid on their surfaces flows toward the drain.”
Additionally, in the Tile Council of North America (TCNA) Handbook, all bathtub and stall shower details contain this note: “All horizontal surfaces—for example shower seats, sills, curbs, etc.—must slope towards drain or other surface sloped toward drain.” Where present, waterproofing also must be sloped.
In a stall shower, the plumbing code requires the floor be sloped 1/4” per foot in order to carry the water effectively to the drain. This would mean that if the measurement from the corner (which is the longest distance from the drain) is 48”, the floor must slope 1” from that corner downward to the drain.
All these notes and standards clearly show that all surfaces in a shower—be it residential or commercial—must carry the water to the drain and therefore, must be sloped. This would include other surfaces in the shower such as the curb or threshold under the door, the shelves of a niche, a corner shelf, a shaving shelf, a seat and a windowsill.
In the attached photo, obviously these requirements were not followed. This shower, in an upscale hotel, included a window (and sill) between the shower and the bathroom. It is easy to see the puddled water on the sill, which is actually sloped not toward the drain but the window. Each time the shower is used, water collects on the sill, remaining there until the cleaning staff dries the surface. Unfortunately, this standing water has found its way to the other side of the wall, causing the drywall to deteriorate.
Attention to this and other details in wet areas will provide a shower that will remain beautiful and functional for many years. Similarly, using qualified labor such as a Certified Tile Installer (CTI) or journeyman installer assures the end user that this type of problem does not occur.