The finished dam or threshold of a shower receptor must be at least how many millimeters lower than the outside floor?

The finished dam or threshold of a shower receptor is required to be at least 25.4 millimeters lower than the outside floor to ensure proper drainage and to prevent water from escaping the shower area. This specific measurement is critical for maintaining sanitary conditions within the shower and for preventing water damage to adjacent areas.

A threshold that is set at this height allows for effective water containment while accommodating the standard dimensions and inclines of flooring installations. It promotes the overall functionality of the shower, ensuring that water flows towards the drain rather than pooling outside the designated area. This is particularly important in avoiding slip hazards and maintaining the integrity of the surrounding flooring materials.

The other measurements provided do not align with the established guidelines for shower receptor design, which are based on best practices for preventing water accumulation and ensuring proper use of the shower space.