For permeable materials in bathrooms/kitchens, the maximum membrane thickness is not to exceed what value?

• A. 18 ng
• B. 15 ng
• C. 20 ng
• D. 25 ng

Answer: (A)

A permeable-material installation in wet areas relies on a membrane that is strong enough to waterproof while thin enough to allow proper bonding and a flush surface. The value you should use is the maximum thickness specified by the membrane system you’re employing. Staying at or below that limit ensures the thinset can properly bond to the membrane, the finished tile height remains consistent with surrounding surfaces, and the waterproofing layer performs as intended. Exceeding the specified thickness can create bond failures, voids, or height issues that compromise both function and finish. Always check the product data sheet for the exact upper limit and adhere to it.