The finished exterior size of a shower in a single-family home must be at least how many inches?

• A. 28 inches
• B. 30 inches
• C. 34 inches
• D. 32 inches

Answer: (D)

The key idea is that the required size is measured as the finished exterior, not just the inner usable space. In residential code, a shower stall typically needs at least a 30 by 30 inch interior opening for functional use. When you account for the wall construction around the shower—the framing, tile, and other finishing materials—the exterior dimensions are larger. A common, practical calculation adds about 1 inch of thickness on each side, making the finished exterior size at least 32 inches by 32 inches. That’s why 32 inches is the minimum finished exterior dimension. The smaller options would not provide enough space once walls and finishes are included, while the larger option isn’t required for a minimum.