Photo 1: This installation, with its hand-molded tiles and curving shapes, is just one example of the creativity and flexibility of tile in a shower environment.


Photo 2: Mortar can be used to create a strong, water-resistant setting bed in virtually any shape or size.

Home owners have several options regarding stall showers ranging from one-piece composite or cast units, to multi-section units, available in a variety of configurations such as square, rectangular, and neo-angle, and made from a cast or resin-laminated materials, to ceramic tile.

Tile is one of the most flexible of all shower materials because, unlike factory-made, cast or laminated units that are available in a limited range of sizes and shapes, showers made with tile can be built to any size or shape. As well, showers made with tile can be the most durable if built properly. Showers made with tiles and a factory-made base (or receptor), are also limited in size and shape and are not included in this article, which begins with all-tile showers.

Photo 3: This curved-wall shower was made with porcelain mosaics installed over a mortar bed. Layers of 15-lb. tar paper sealed with asphalt gum are located behind the mortar setting bed to help control moisture.

There are few restrictions to the size and shape of an all-tile shower installed over a mortar setting bed (Photo 1), but there are significant differences in the way a mortar bed shower can be built (Photo 2) and “water-proofed” - or more accurately, the way the mortar bed is moisture managed. There are a number of moisture-management systems and materials that allow all-tile showers to be built with little or no mortar required. Mortar beds no longer have a monopoly on shower stall construction, but regardless of the materials or method of construction, the most important issue is how the installation is equipped to handle the moisture it will be exposed to once it is put into service (Photo 3).

Traditional Mortar Setting Beds

Like any other construction material, there is good mortar and there is mortar of sub-standard quality. Assuming that a mortar bed is dense with a low relative porosity (compared to a mortar bed that is poorly proportioned, mixed, or applied), the issue is where best to locate the moisture management system - behind the mortar bed, or on its surface. Traditionally, a mortar bed’s cleavage membrane, installed to prevent moisture wicking from the fresh mortar and considered by some installers to be a “waterproofing” membrane, is located between the mortar bed and the wall or floor structure. In this type of application, a tar paper or plastic film membrane, if properly sealed and joined, can provide a moderate to good level of moisture management protection. A down side to this method occurs when an installation is not allowed to dry out between uses and the mortar bed becomes water-logged and a potential safe harbor for mold and mildew to invade.

Photo 4: Michael smoothes the manufactured gripping surface of a molded, two-piece sloped shower floor. A companion to the floor sections, the wide bonding-flange drain requires no clamping and only thinset mortar for its installation and that of the system’s adjustable drain screen (Sloped floor and drain from KERDI system).

Shower Pans

Traditional shower pans, made from lead, copper, or synthetic sheets, and joined to a clamping-type drain, have been the heart of shower construction for many years. In many areas, the clamping-type drain is the only acceptable drain for a shower stall, but a new type of drain, known as a bonding flange drain, is gaining acceptance because it does not depend on traditional setting bed mortar (Photo 4). In place of a pan or membrane, another method simplifies the process (at the expense of a limited range of dimensions and shapes) with a one-piece, watertight, ready-to-tile setting bed that incorporates a sloped floor, upturned walls, and an integral curb.(Photo 5)

Photo 5: Tiles can be installed directly over the surface of this water-tight, lightweight, one-piece shower pan (TileRedi pan).



Photo 6: A factory-made sheet membrane system was used to protect this corner stall shower, its curb, and the adjoining bathroom floor (Nobleseal TS).

Surface-Applied Membrane Systems

An alternative method to protecting a mortar bed floor still requires the traditional cleavage membrane (needed for all unbonded mortar beds) to protect the fresh mortar, but once the bed hardens, moisture management is provided by a loads-bearing, surface-applied membrane made specifically for use with tile. Such systems are available in two forms: factory-made sheet that is laminated on-site (Photo 6); or a trowel-applied system composed of a reinforcing fabric and a liquid, paste, or gel (some systems may not require the use of the fabric) that is applied to surfaces on-site in one or more coats (Photo 7). The advantage of these systems is they isolate the setting bed from moisture, and limit penetration to the tiles, adhesive layer, and grout.

In addition to protecting mortar setting bed, surface-applied systems (depending on the brand) can be used to protect other suitably strong materials such as concrete, plywood, cement backer boards, and self-leveling underlayment. They can also be applied to most non-mortar, factory-made shower components such as benches, inset boxes, and sloped floors.

Photo 7: A trowel-applied membrane system on this barrier-free shower stall, is being applied to a factory-mad, sloped floor made of high-density expanded foam (ProSpec B-6000).

There are several methods for creating a shower’s sloped floor. The traditional way, after the walls are prepared, is to create a sub-floor for the shower that slopes to the clamping drain’s weep holes, install a shower pan, test it, and if it passes, cover the pan with approximately 1-1/2” of setting bed mortar, a layer of thinset mortar, and tile. With another method, manufactured (Schluter) sloped floor sections and a non-clamping-type drain - called a bonding flange drain - are installed and covered with a membrane (Photo 4). Most sloped floor sections, regardless of manufacturer, are made of some type of water-resistant, expanded foam.

Photo 8: This manufactured offset flange is useful when the local code requires a clamping-type drain and a surface-applied membrane is specified (NobleFlex).

A drawback of most foam substrates is their inability to support high point loads, such as an occupied wheelchair. For this type of application, only a densely packed mortar bed will do. When a mortar bed is required and a surface-applied membrane is specified, a bonding flange drain can replace a traditional clamping-type drain. When a surface-applied membrane is specified and only a clamping drain is accepted by the local building code, a useful method of building a sloped shower floor is by using an offset flange (Photo 8) to connect a surface-applied sheet membrane to a traditional clamping-type drain (Photo 9). Once the pan is installed and water-tested for leaks, tiles can be installed directly over the membrane (Photo 10). The same manufacturer (Noble) also produces a lightweight, sloped, modular shower floor base that is already covered with a membrane.

Photo 9: Once the pan portion of this sheet membrane system is installed and tested, the dished-out area surrounding the drain is filled with mortar and the floor covered with tile.



Photo 10: These face-mounted rocks are installed directly over the membrane applied to the sloping floor.



Resources:

  • Photos courtesy of Mike Mesikep and Paul Winn.
  • Tiles courtesy Michelle Griffoul Studios
  • Tile Redi pan: www.tileredi.com
  • Schluter Kerdi system: www.schluter.com
  • NobleFlex, Nobleseal TS: www.noblecompany.com
  • ProSpec B-6000: www.prospec.com