What is the minimum width of metal flashing required for a valley with asphalt shingles?

What is the minimum width of metal flashing required for a valley with asphalt shingles?

• A. 24 inches
• B. 16 inches
• C. 8 inches
• D. 10 inches

Answer: (A)

Valleys must be flashed with enough width to cover under the shingles on both sides and provide a continuous water channel. For asphalt shingles, you typically flash at least 12 inches up each side of the valley, giving a total width of 24 inches. This ensures the flashings extend far enough under the shingles to be protected from weather and helps prevent leaks if shingles shift or overlap. Narrower widths, like 8, 10, or 16 inches, generally don’t provide enough coverage and can lead to water infiltration where the valley is most vulnerable.

Valleys must be flashed with enough width to cover under the shingles on both sides and provide a continuous water channel. For asphalt shingles, you typically flash at least 12 inches up each side of the valley, giving a total width of 24 inches. This ensures the flashings extend far enough under the shingles to be protected from weather and helps prevent leaks if shingles shift or overlap. Narrower widths, like 8, 10, or 16 inches, generally don’t provide enough coverage and can lead to water infiltration where the valley is most vulnerable.