What type of liner material must be used for walls and floor framing in on-site built-up shower receptors?

The correct answer pertains to the materials that are permissible for use as liners in on-site built-up shower receptors, which are primarily intended to manage water drainage and prevent moisture damage to the surrounding structure. The International Residential Code (IRC) stipulates that the liner materials must be capable of providing a watertight seal and resist the deleterious effects of moisture.

Sheet lead, copper, or plastic are appropriate materials for these applications. Sheet lead is highly durable and water-resistant, making it an effective barrier against moisture. Copper offers excellent longevity and resistance to corrosion, ensuring a stable, long-lasting moisture barrier. Plastic liners, such as those made from PVC or similar materials, are also favored due to their ease of installation, flexibility, and resistance to mold and mildew.

In contrast, other materials such as vinyl or fiberglass, while often used in pre-fabricated shower units, do not meet the specific requirements outlined in the IRC for custom-built receptacles, where the liner must provide structural integrity and be compatible with the construction method of the shower base. Wood or metal is also unsuitable as these materials can degrade over time due to exposure to water.

Thus, the combination of sheet lead, copper, or plastic serves to ensure that the built-up shower