Valley Leaks
A valley is where two roof planes meet, and it carries the runoff from both. More water passes through a valley than anywhere else on the roof, which is why it is unforgiving of shortcuts.
Open and closed valleys
An open valley has exposed metal down the centre, with shingles trimmed back from it. A closed valley has shingles woven or cut across it with the metal hidden underneath.
Open valleys shed debris better and are easier to inspect. Closed valleys look cleaner and are more common on Sacramento tract housing. Both work when installed correctly.
Why valleys fail
- Debris accumulation — leaves and needles dam the valley and force water sideways under the shingles
- Corroded or undersized valley metal on older roofs
- Nails driven too close to the centre of the valley, which puts fasteners directly in the water path
- Missing or inadequate underlayment beneath the metal
- A previous repair that ran sealant down the valley instead of replacing the metal
The Sacramento debris problem
Homes under mature oaks, pines or liquidambars collect a great deal of material in the valleys through summer and autumn. Then the winter storms arrive and the valley is already dammed.
Clearing valleys before the rains is one of the cheapest things a homeowner can do, and it prevents a disproportionate share of winter leaks.
Proper repair
- Shingles cut back and the old valley metal removed entirely
- New underlayment laid in, then new valley metal of adequate width
- Shingles trimmed and fastened clear of the water path
- Rotted sheathing beneath replaced — valleys concentrate water, so rot here is common
Common questions
Why does my roof leak where two sections meet?
That is the valley, and it carries the runoff from both roof planes. Debris damming, corroded metal, or nails placed in the water path are the usual causes.
Should I clean my roof valleys?
Yes, before the rainy season, especially under mature trees. Do it from a ladder or hire someone — walking a roof to clear valleys is how people fall.