How to Install a Closed-Cut Valley With Laminated Shingles
One side runs through, the other is trimmed back 2 inches from the centreline and sealed. A clean valley with no exposed metal.
- Advanced
- 2 to 4 hours per valley
- Updated
The short answer
In a closed-cut valley, shingles from the first roof plane run straight across the valley and up the other side by at least 12 inches. Shingles from the second plane are laid over them, snapped and cut about 2 inches back from the valley centreline, with the upper corner clipped about 1 inch. The cut edge is bedded in a band of roof cement, and no nail goes within 6 inches of the centre.
A closed-cut valley, sometimes called a California cut, hides the valley under shingle. There is no exposed metal, so the roof looks uniform from the ground, and the method is approved by most manufacturers for laminated shingles. It is also the valley that depends most on workmanship, because the cut edge and the membrane underneath are all that stand between the valley flow and the house.
The principle is simple: one roof plane's shingles run all the way through the valley and lap onto the other side, forming a continuous water barrier, and the second plane's shingles are cut back and laid over them. Water from the second plane runs down its cut edge onto the through-run shingles, and from there down the valley. Start with valley prep, and compare other methods in open, closed-cut and woven valleys explained.
Tools
- Hook blade utility knife
- Chalk line
- Tape measure
- Roofing hammer or coil nailer
- Caulking gun or trowel for roof cement
- Cut resistant gloves
- Scrap of plywood or shingle to cut over
Materials
- Ice and water shield, 36 inch wide roll
- Laminated asphalt shingles approved for closed-cut valleys
- Roofing nails, 1-1/4 inch
- Asphalt roof cement, for sealing the cut edge
- Underlayment for the field
Safety first
- Work tied off. The valley is a funnel, and a fall down either plane goes straight to the eave. WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall could cause serious injury.
- Cut shingles with the blade pointing away from your body and your other hand clear, always cutting over a scrap to protect the course below.
- Roof cement is a skin irritant and sticky. Wear gloves and keep it off the shingle surface where it can stain.
Step by Step
Step 1: Prep the valley and confirm the method is approved
Follow how to prep a roof valley: sound deck, 36 inch membrane centred on the valley, no nails near the centre. The closed-cut valley has no metal to catch water that finds its way past the cut edge, so the membrane does all of that work.
Check the shingle instructions. Some products limit closed-cut valleys to certain pitches or call for specific cutline distances and nail setbacks, and those numbers replace the ones here.
Step 2: Decide which plane runs through
The through-run shingles form the bottom layer of the valley and the cut shingles lap over them. Common practice is to run the lower-pitch plane through first, so the faster water from the steeper plane sits on the top layer and runs down its cut edge onto the shingles beneath. On equal pitches either side can run first. See valleys with unequal pitches for the detail when pitches differ.
Start both planes at the eave with starter course and keep the course lines level across the valley so the courses meet.
Step 3: Run the first plane through the valley
Lay each course of the first plane all the way across the valley and at least 12 inches up the other roof plane. Press each shingle down into the valley so it follows the corner and is not bridging. A shingle that bridges will crack when someone steps on it or when the roof loads up with snow.
Nail the shingles so that no nail is within 6 inches of the valley centreline on either side. Move the nails up out of the valley zone and use extra nails farther back if the shingle needs holding, following the manufacturer's nailing instructions.
Watch out: Do not nail into the valley centre, even one nail. Keep the whole strip 6 inches either side of the centre free.
Step 4: Shingle the second plane up to the valley
Lay each course long so the end rests over the first plane's shingles, then trim it after you snap the line. Do not cut as you go. Shingle every course of the second plane to the valley and trim afterward, so the cutline is straight.
Keep nails at least 6 inches from the valley centre on this side too.
Step 5: Snap the cutline 2 inches from the centre
Measure from the centre of the valley, the lowest point in the corner, and snap a line 2 inches toward the second plane. A 2 inch setback leaves the cut edge close enough that water from the second plane runs into the valley, while keeping it off the very centre where the most water flows. Some manufacturers ask for different distances, so follow the wrapper.
Keep the line straight. A wavy cutline makes the valley look sloppy and leaves uneven gaps.
Step 6: Cut the shingles and clip the upper corners
Lift the shingle, slide a scrap under it to protect the shingle below, and cut from the top with a hook blade. Do not cut through the first plane's shingle below. The cut should score the top layer only.
Clip the top corner of each cut end at about 45 degrees and about 1 inch from the corner. The clip stops water running down the valley from being driven under the pointed corner. See how to cut asphalt shingles for clean, safe cuts.
Tip: Cutting each shingle after it is laid is slower, but the chalk line method makes a straight valley that looks professional from the street.
Step 7: Bed the cut edge in roof cement
The cement should sit under the cut edge and spread back about 3 inches, but no closer to the centre than the edge itself. Press down firmly. A cut edge sealed this way will not curl or lift in wind and will not let water creep under it.
Wipe away any squeeze-out. Cement on the face of the shingle stains and collects grit.
Step 8: Check the valley and the bottom end
Run your hand down the valley. The shingles should lie flat with no humps, no exposed nails and a continuous straight cut. If a shingle is lifting, press it down and add cement.
At the eave, trim the shingles to the drip edge and confirm the valley membrane and shingles lead into the gutter. If the valley dies into a wall or lower roof, see how to fix a dead valley.
Why Closed-Cut Valleys Fail
When a closed-cut valley leaks, the cause is almost always one of four things: a nail near the centre, a cut edge not sealed and lifting, a shingle bridging the corner and cracking, or debris packed against the cut edge that keeps it wet. Because the metal is hidden, there is no backup. The membrane under the valley is the only barrier.
That is also why closed-cut valleys are a poorer choice under conifers, where needles pile against the cut edge and stay wet. See roof valley types for when an open valley is better.
Shingle Thickness
Laminated shingles are thick, and a closed-cut valley has two layers at the valley. Some products are too thick or stiff to press cleanly into a tight corner, and manufacturers may prohibit closed-cut valleys for those products or on low slopes. Always check.
Common Mistakes
- Nailing within 6 inches of the centre. Every nail there is an open hole in the valley, and is the most common closed-cut leak.
- Not sealing the cut edge. An unbedded edge lifts in wind and lets water creep under it.
- Cutting through the shingle below. Slicing into the through-run shingle opens a direct path to the membrane. Cut over a scrap and score only the top layer.
- Not clipping the corners. A pointed corner directs water under the shingle instead of down the valley.
- Bridging the corner. Shingles not pressed into the valley crack under foot or snow load.
- Wavy cutlines. They look bad and leave inconsistent gaps that trap debris.
- Using the method on a product that prohibits it. Check the wrapper first.
When to Call a Professional
If the roof is steep, the valleys carry very different pitches, the valley runs into a wall or a lower roof, or the shingles are a heavy laminated product with tight instructions, a roofer should build it. Closed-cut valleys hide their own failures, so getting it right the first time matters.
If an existing closed-cut valley is leaking, a roofer can lift the cut edge, check for nails and a missing seal, and decide whether to repair or rebuild it as an open valley. See how to repair a leaking valley.
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 Closed-Cut Valley: Questions
What is a closed-cut valley?
A closed-cut valley is a shingle valley with no exposed metal. Shingles from one roof plane run all the way through the valley and at least 12 inches up the other side. Shingles from the second plane are laid over them and trimmed along a chalk line about 2 inches from the valley centreline, with the cut edge sealed in roof cement.
How far from the centre do you cut a closed valley?
A common cutline is 2 inches back from the valley centreline on the plane that is cut. The top corner of each cut end is clipped about 1 inch so water does not get driven under it. Some shingle manufacturers give a different distance, so follow the installation instructions printed on the wrapper for your product.
Which side of a valley gets shingled first?
The plane that runs through the valley goes first, and the other plane is cut and lapped over it. Common practice is to run the lower-pitch plane through first so the faster water from the steeper plane is carried on the top layer. When both planes have the same pitch, either side can go first.
How far should nails be from a closed valley centre?
Keep nails at least 6 inches from the valley centreline on both planes, or farther if the shingle manufacturer says so. Nails closer than that are holes in the highest-flow part of the roof. If a shingle needs more holding power, add fasteners farther up the shingle, not in the valley.
Is a closed-cut valley as good as an open valley?
A well built closed-cut valley performs well and is widely approved for laminated shingles. It depends more on workmanship, because the cut edge and the membrane do all the work and there is no metal backup. An open metal valley sheds water faster and is easier to clean, which matters under trees.
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.
Want someone to look at your roof?
Kory & Johnny have roofed homes across the Fraser Valley since 2016. Free inspections, honest estimates, no pressure.
604-728-0146Text UsEmailServing Hope, Agassiz, Chilliwack, Rosedale, Abbotsford & the entire Fraser Valley