A roof valley is the inside angle where two roof slopes meet and slant toward each other. It works as a channel: rain and melting snow from both slopes run down into it and off the roof. Because so much water funnels through that one line, a valley is one of the busiest, and most leak-prone, places on a roof.
Where are the valleys on my house?
Look from the street. Wherever a roof has an L shape, a dormer, an addition or a cross gable, there is usually a valley where the new roof plane meets the old one. The outer opposite is a hip, and the peak is a ridge; see what is a ridge cap. A simple rectangular gable roof may have no valleys at all, while a more complicated roofline can have several.
Why are valleys leak-prone?
- Volume. Water from two slopes arrives at once, so more water crosses the same narrow strip.
- Debris. Leaves, seeds and granules gather in the channel and slow the flow.
- Overlap complexity. Several materials meet in one line, and mistakes in layering show up here first.
- Wear. Tree limbs, ice and sun work the same strip repeatedly.
What are the main valley styles?
| Style | How it looks | How it works | Things to ask |
|---|---|---|---|
| Open valley | A strip of metal or other lining visible down the middle, shingles trimmed back on each side | Water runs on the lining, which is the weather surface | What lining is used, and how is it fastened? |
| Closed valley, woven | Shingles from both slopes interlace across the valley, so no lining shows | Shingles are layered over each other, often over an underlayment layer | Is this method allowed for the product, and what goes underneath? |
| Closed valley, cut | One slope's shingles run through, the other side is cut along a line | The cut edge is laid over the through shingles | What is under the cut, and how is it sealed? |
Each has supporters. Our crews' view is that how well the layers underneath are done matters more than which style is picked, but that is an opinion, not a rule. The manufacturer's instructions for your shingle line say which valley methods are allowed.
What goes under a valley?
The valley is a place where extra water protection is common. Many installers add a self-adhering membrane or a dedicated layer below the visible surface. We describe one such product in what is ice and water shield. The layers are part of the scope; confirm them in writing. For metals and other detail pieces, read what is flashing.
How do I know if a valley is leaking?
You may see a ceiling stain under the line of the valley, damp insulation in the attic, or staining on the wall below where the valley ends. A leak can show up far from where water enters, so do not assume the stain is directly below the problem. See how to find a roof leak. Observe from the ground and from inside the attic, and do not climb onto a roof to check a valley, since a wet or slick valley is a poor place to stand.
What does valley work involve on a new roof?
- The old valley material is removed in tear-off.
- The deck under the valley is checked.
- Underlayment, and any extra membrane, is laid in the valley line.
- Metal lining is installed if the plan is an open valley.
- Shingles are installed up to or across the valley according to the chosen style.
- The valley is checked for debris and clean runoff at the bottom.
This sits within the overall list in what a roof replacement includes.
Frequently asked questions
Is an open valley better than a closed valley? Neither is better in every case. Each can perform well when installed to the manufacturer's instructions. Ask your roofer why they prefer one for your house.
Can a valley be repaired without replacing the roof? Sometimes, depending on the cause and the age of the roof. A roofer needs to inspect it to say.
Do valleys need cleaning? Debris in a valley can slow water. A roofer can advise on maintenance, and you should not climb up yourself to clear it.
Does a valley leak mean the shingles are bad? Not necessarily. Valley leaks often come from layering, flashing or debris issues rather than shingle defects.
Is a valley a problem for hail or wind? Any roof surface can be affected by weather. That is a question for an inspection, and any insurance question goes to your agent.
Talk to us about your roof
If you suspect a valley problem, Total Roof Protection OKC can inspect it and explain what we see. Call 405-415-5841 to arrange it. Our inspection reports on the roof and does not promise any particular result.