Waterproofing and Wet Area Applications
Waterproofing and Wet Area Applications
Wet areas such as showers, steam rooms, and exterior installations require waterproofing to protect substrates and prevent mold. For LFT, waterproofing membranes (sheet or liquid) must be applied over a properly sloped substrate (1/4 inch per foot to drain). ANSI A118.10 covers waterproof membranes. In showers, a pre-sloped shower pan is required; waterproofing must extend up walls at least 6 inches above the curb and to the showerhead height (or per code). For steam showers, waterproofing must cover the entire enclosure. Vapor barriers may be needed. Traps: installing LFT directly on drywall in wet areas; skipping the pre-slope; and not using a waterproof membrane in steam showers. Worked example: A shower with a 4-foot by 5-foot footprint requires a pre-sloped mortar bed, a waterproof membrane (e.g., liquid applied) covering the floor and walls up to 6 feet, and a sealant at all changes of plane. Use a 1/2-inch notch trowel and back-butter the LFT to achieve 95% coverage.