How to Install a Woven Shingle Valley (and Why Laminated Shingles Do Not Weave)
Courses from each plane interlaced across the valley. Quick with thin 3-tab shingles, and usually not approved for laminated ones.
- Advanced
- 2 to 3 hours per valley
- Updated
The short answer
A woven valley interlaces shingle courses from both roof planes across the valley, alternating one course from each side, with no metal. Each shingle is pressed into the corner, extends at least 12 inches onto the opposite plane, and is nailed at least 6 inches from the centreline. It suits 3-tab and other thin shingles. Most laminated shingles are not approved for weaving because the stacked layers dam water.
The woven valley is the oldest shingle valley, and the one with the least going on: no metal, no cutline, no cement. Shingles from each plane run straight across the valley and onto the other side, one course from the left, the next from the right, so every course is lapped over and under the courses around it. The valley ends up with two layers of shingle everywhere, and water runs over the top of it with no exposed edge to catch.
It sounds ideal and, with the right shingle, it works. The catch is that it only works with thin shingles. Laminated shingles are thick, and two or three layers stacking up at every course create a raised ridge at the valley centre that dams water and stops the shingles lying flat. Most laminated shingle manufacturers prohibit it. Check the wrapper, and if it is not approved, use an open valley or a closed-cut valley instead. To compare all three, see roof valley types.
Tools
- Roofing hammer or coil nailer
- Hook blade utility knife
- Chalk line
- Tape measure
- Hand roller for pressing shingles into the corner
Materials
- Ice and water shield, 36 inch wide roll
- 3-tab or other shingles approved for woven valleys
- Roofing nails, 1-1/4 inch
- Underlayment for the field
Safety first
- Work tied off. Both planes slope into the valley, so a slip at the valley takes you down either one. WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall could cause serious injury.
- Warm 3-tab shingles are soft and slippery with granule dust. Wear shoes with clean, flexible soles and keep the valley swept.
- Shingle bundles stored on a valley flatten it and crack the membrane. Stack them on the ridge or a flat area, not across the valley.
Step by Step
Step 1: Confirm the shingle is approved for weaving
Woven valleys are commonly approved for 3-tab and similar thin shingles and prohibited for most laminated products. Some manufacturers also limit weaving to moderate or steep pitches and exclude low slopes, where a woven valley holds water.
If the wrapper does not mention woven valleys, do not guess. Choose one of the other methods.
Watch out: Weaving a laminated shingle that is not approved can void the shingle warranty and produces a thick ridge that dams water.
Step 2: Prep the valley membrane
A woven valley has no metal, so the membrane is the only waterproof layer below the shingles. Follow how to prep a roof valley in full, and lap the field underlayment over its edges.
Because the shingles cover the membrane completely, there is no way to see a problem later. Check the membrane for wrinkles and pressed-in air pockets before you cover it.
Step 3: Shingle both planes up to the valley with long courses
Do not trim shingles at the valley. Lay each course from one plane across the valley and at least 12 inches onto the other plane. Course lines on both planes should match across the valley, so check them regularly with a chalk line.
Keep the courses level at the eave so they line up when they meet at the valley.
Step 4: Lay the first course across the valley
Press the shingle into the valley with your hand or a roller so it follows the angle of the corner. A shingle that bridges will crack under a footstep and loosen under snow load. Work from the valley centre outward on each plane.
Nail the shingle at least 6 inches from the valley centreline, or farther if the manufacturer says so. Keep all nails out of the centre strip.
Step 5: Lay the next course from the opposite plane
This is the weave. One course crosses from the left plane, the next from the right, and each one lies over the last. Because the planes meet at a valley line rather than a flat, each shingle has to follow the bend and stay bedded. Work carefully so the shingles stay flat and sealed to each other.
Offset the courses as the pattern on the wrapper calls for, so joints between shingles do not line up from course to course.
Step 6: Alternate up the valley, pressing each course in
Every course has the same method: press into the corner, nail outside the 6 inch zone, and lap over the course below. If the shingles start to stand up at the valley, stop and check that the membrane is flat and the shingles are not stacking up.
Work steadily. A woven valley is quick once the rhythm is set, but one bridged shingle in the middle of the valley shows up as a hump the full length of the roof.
Step 7: Finish at the top and check the valley
At a ridge, the valley shingles run up to the ridge and are covered by the cap. See how to install hip and ridge cap for the cap detail.
Look down the valley from above: it should be an even, continuous line, slightly depressed at the centre, with no exposed nail heads and no humps. Press any lifted shingle down.
Why Laminated Shingles Do Not Weave Well
A 3-tab shingle is a single layer of asphalt and granules, roughly 1/8 inch thick. A laminated shingle is two layers laminated together and is thicker and stiffer, and in places as much as double. When you weave these, the valley builds up as many as three or four layers of thick material at each course, which makes a raised ridge down the valley centre. Water running down one plane meets the ridge and backs up, and the shingles stop sealing down tightly.
Stiffness also makes the shingles difficult to press into the corner. They bridge instead of bending, and a bridging shingle cracks under snow load or foot traffic. These are the reasons most laminated shingle manufacturers prohibit weaving and approve open or closed-cut valleys instead.
Where Woven Valleys Fail
A woven valley fails when nails are driven near the centre, when shingles bridge the corner, when debris stays against the valley ridge, or when an old valley is overlaid on a new layer and builds too thick. Because nothing is exposed, the first sign is a ceiling stain. On an existing roof, see how to repair a leaking valley.
Common Mistakes
- Weaving laminated shingles. Thick layers dam water in the valley centre and most manufacturers prohibit it.
- Nailing near the centreline. A nail within 6 inches of the valley centre leaks under a woven valley just as it does in any other.
- Bridging the corner. A shingle not pressed into the angle cracks under foot or snow load.
- Skipping the wide membrane. With no metal and no exposed edge, the membrane is the only backup.
- Using a woven valley on a low slope. Below moderate pitches the valley holds water and the method is usually not approved.
- Stacking bundles in the valley. The weight crushes the membrane and flattens the corner.
When to Call a Professional
If you are not sure whether the shingle is approved for weaving, or the roof is steep, tall or has valleys with very different pitches, have a roofer build it. A roofer will often recommend an open or closed-cut valley instead, which are more forgiving.
If an existing woven valley is leaking, the repair may mean stripping the valley to the membrane and rebuilding it with a different method.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Repair service or the towns we cover.
How to Install a Woven Valley: Questions
What is a woven valley?
A woven valley is a shingle valley with no metal, where shingle courses from both roof planes run across the valley and lap over each other in alternating order. Each course is pressed into the valley corner and nailed at least 6 inches from the centreline. It is traditionally built with 3-tab shingles and works best on moderate to steep pitches.
Can you weave architectural shingles in a valley?
Most manufacturers say no. Laminated shingles are thick and stiff, and weaving stacks multiple layers across the valley, creating a ridge that dams water and stops shingles from lying flat. Use an open metal valley or a closed-cut valley instead, and check the installation instructions on the wrapper for the methods approved for your shingle.
Is a woven valley better than a closed-cut valley?
Not necessarily. A woven valley has two layers of shingle everywhere and no cut edge, which is an advantage with thin shingles. A closed-cut valley is approved for more products, especially laminated shingles, and can be sealed at the cut edge. The best choice depends on the shingle, and the manufacturer's instructions decide.
How far from the valley should you nail a woven valley?
Keep nails at least 6 inches from the valley centreline, and farther if the shingle manufacturer specifies it. Nails closer than that create holes in the highest-flow part of the roof. The wide membrane underneath seals around the nail, but nails in the centre strip remain the most common cause of woven valley leaks.
Related Guides
All Roof Valleys guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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