Roofing Glossary

Valley

A valley is the V-shaped channel formed where two roof slopes meet at an inside angle — like where a dormer or addition joins the main roof. Every drop of rain landing on both slopes funnels through the valley, making it the highest-water-volume area on the roof.

Because valleys handle so much water, they get special treatment: metal or membrane valley flashing underneath, and shingles woven, cut, or left open across the channel. A properly built valley sheds water fast; a poorly built one is one of the most leak-prone spots on any roof.

Valleys also collect leaves and debris, which can dam water and force it sideways under shingles. Keeping valleys clear is basic roof maintenance.

Why It Matters

Valleys fail more often than any other roof feature except flashing. If your roof is aging, the valleys usually show it first — they are a priority check in any roof inspection.

What to Watch For

• Missing granules or worn shingles in the valley channel
• Leaves and debris packed into valleys
• Stains on ceilings below a valley line

A Maryland Note

Maryland's heavy leaf fall each autumn clogs valleys fast. A valley full of wet leaves holds moisture against the shingles for weeks.

Questions about your own roof? Request a free estimate or call Nucci Brothers Roofing at (301) 458-1003.