When installing step flashing at a roof-to-wall intersection in California, what is the minimum overlap requirement between adjacent pieces of step flashing?
Correct Answer
B) 3 inches
Per CRC Section R903.2.1, step flashing pieces must overlap each other by a minimum of 3 inches. Each piece should be at least 4 inches wide with 3-inch overlap to ensure continuous water protection. This requirement is critical in California where seismic movement and thermal cycling can stress flashing connections.
Why This Is the Correct Answer
CRC Section R903.2.1 mandates a minimum 3-inch overlap between adjacent step flashing pieces. This overlap, combined with each piece being at least 4 inches wide, creates a continuous water barrier. California's seismic activity and thermal cycling make this overlap especially critical because building movement can open small gaps; 3 inches provides enough redundancy to stay watertight.
Why the Other Options Are Wrong
Option A: 1 inch
1 inch is far too small. A 1-inch overlap would leave nearly no margin against the lateral water movement caused by wind-driven rain or the micro-movement from California's seismic activity and thermal expansion cycles, creating a high risk of infiltration at every overlap joint.
Option C: 2 inches
2 inches is insufficient under CRC R903.2.1. While it might seem close to the code minimum, it falls 1 inch short of the 3-inch requirement and would not provide the redundancy needed to handle California's seismic movement and wind-driven rain conditions.
Option D: 4 inches
4 inches exceeds the code minimum, so it is not the minimum requirement the question asks for. The code sets 3 inches as the floor; using more is permitted but does not define the required minimum.
Memory Technique
Think '4 and 3': each piece is 4 inches wide, pieces overlap 3 inches. Visualize a staircase — each step is 4 wide but sits 3 inches under the one above it.
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