Roofing Glossary

California (Long Island) Valley

A California valley — also called a Long Island valley — is a shortcut valley style: the shingles from one roof slope are run straight through the valley, and the shingles from the other slope are cut and butted against them, often with a vertical cut line down the valley center.

California valleys are fast to install, which is their entire appeal. Their weakness is the butt joint: water running down the valley strikes the cut ends of the butted shingles head-on, and the vertical seam is a natural channel for water to work under. They rely heavily on sealant and the valley lining beneath.

Most shingle manufacturers do not recommend California valleys, and they are a frequent source of valley leaks on production-built homes where speed was prioritized.

Why It Matters

If your home has California valleys and they leak, the durable fix is rebuilding them as proper closed-cut or open valleys — not more sealant on a fundamentally weak detail.

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