A hip roof with dormers is one of the most complex roof shapes to shingle, and the dormers are where most mistakes happen

A hip roof slopes down on all four sides, and each dormer punches a hole through that slope. You will be cutting and fitting shingles around four separate roof valleys, four separate step flashing details, and four separate ridge caps. The work moves slower than a straightforward gable roof because every shingle near a dormer requires a cut, and because the valleys and flashing have to shed water reliably or you will have leaks inside the walls.

The sequence matters: frame the dormers and install flashing before you shingle, shingle the main roof first, then shingle each dormer, then seal the valleys where they meet. If you shingle the dormers before the main roof, you will tear them up when you walk on them. If you skip the step flashing or install it wrong, water will run behind it and rot the dormer walls.

Key Takeaways

  • Install all step flashing and valley flashing before you lay the first shingle, because you cannot go back and tuck it under shingles that are already nailed down.
  • Shingle the main hip roof first, then shingle each dormer, so you do not damage the dormer shingles when you walk on the roof.
  • Valleys where dormers meet the main roof need to be at least 6 inches wide on each side and flashed with either metal valley material or woven shingles, depending on your climate and roof pitch.
  • Step flashing at the dormer walls must overlap the shingles below it and be sealed with roofing cement, and each piece must be nailed only to the dormer wall, not to the roof shingles.
  • A four-dormer hip roof typically takes 40 to 60 hours for an experienced roofer, and mistakes in the valleys or flashing are the most common cause of leaks within five years.

Understanding the roof geometry before you start

A hip roof has four sloped sides that meet at a ridge running down the center. The corners where two slopes meet are called hip edges, and they run diagonally from the ridge to the corners of the house. Dormers are small roof structures that stick up through the main roof, and each one creates a valley on both sides where the dormer roof meets the main roof slope.

With four dormers, you have eight valleys total (two per dormer). Each valley is a low point where water runs downhill, and that is where water collects if the flashing is wrong. The dormers also create four step flashing details where the dormer walls meet the main roof. Step flashing is a series of overlapping metal pieces that direct water down and away from the wall.

Before you order materials, measure the roof pitch (the angle of the slope) and the width of each dormer opening. Steeper pitches shed water faster and allow you to use open valleys. Shallow pitches (under 4:12) need closed valleys or woven valleys to prevent water from backing up. Most residential roofs are between 5:12 and 8:12, which works well for open valleys with metal flashing.

Installing flashing before you shingle

All flashing must go down before the first shingle is nailed. This includes step flashing at the dormer walls, valley flashing where the dormers meet the main roof, and counter-flashing that will tuck under the dormer siding. If you nail shingles first, you cannot slide flashing under them without tearing them up.

Start with the valleys. Measure 6 inches on each side of the valley centerline and snap chalk lines. If you are using open valleys (metal flashing), roll out the valley material along the chalk lines and nail it every 12 inches, staying 3 inches away from the centerline so the nail holes are covered by shingles. If you are using woven valleys (shingles woven together), you will install the flashing after you shingle, but you still need to snap the chalk lines now.

Next, install step flashing at each dormer wall. Step flashing comes in pieces, usually 10 inches wide and 10 inches tall, and each piece overlaps the one below it by 2 inches. Start at the bottom of the dormer wall (where it meets the main roof) and work upward. Nail each piece to the dormer wall only, using two nails per piece, and leave the bottom edge of each piece loose so the shingles can slide under it. The shingles will hold the bottom edge down.

Install counter-flashing at the top of each dormer wall if the dormer has a wall that extends above the roof line. Counter-flashing is a bent piece of metal that tucks under the siding and overlaps the step flashing below. This prevents water from running down the outside of the dormer wall and behind the step flashing.

Shingling the main hip roof

Start at the lowest edge of the main roof and work upward toward the ridge. On a hip roof, the lowest edges are the four sides, not just the eaves. Begin at one corner and shingle in horizontal courses (rows) that run parallel to the eaves, working toward the opposite corner.

When you reach a valley, stop about 12 inches before the valley centerline. Cut each shingle at an angle so it points toward the valley but does not cover the valley flashing. The cut should be clean and straight, and you should use a utility knife or a circular saw with a fine blade. Nail the shingle 6 inches away from the cut edge so the nail does not split the shingle or come loose.

Continue shingling around all four sides of the main roof until you reach the hip edges. At each hip edge, you will have shingles meeting at an angle. Cut the shingles so they overlap at the hip, and cap the hip with a ridge cap shingle (a shingle folded in half along the ridge). Nail the ridge cap with two nails per shingle, one on each side of the ridge, 5 inches from the top.

When you reach the ridge, shingle from all four sides toward the center. The last shingles will meet at the ridge, and you will cap the ridge with ridge cap shingles running the length of the ridge. This is the highest point of the roof, and it is the most visible, so make sure the ridge caps are straight and evenly spaced.

Shingling each dormer and sealing the valleys

After the main roof is shingled, shingle each dormer. Start at the lowest edge of the dormer roof (where it meets the main roof) and work upward toward the dormer ridge. The shingles at the bottom edge should slide under the step flashing you installed earlier. Nail them 6 inches below the top edge of the shingle, which is the standard nailing line.

When you reach the valleys on either side of the dormer, cut the shingles at an angle so they point toward the valley. Do not cover the valley flashing. The cut should be the same angle as the main roof valleys, so water flows straight down the valley without pooling.

After all the dormer shingles are nailed, seal the valleys with roofing cement. Use a caulk gun to explore a bead of cement along both edges of the valley flashing, where the shingles meet the metal. This prevents water from running under the shingles and behind the flashing. Do not use so much cement that it runs down the roof or pools in the valley; a thin, continuous bead is enough.

If you are using woven valleys instead of metal flashing, the shingles from the main roof and the dormer roof will weave together in the valley. After both sides are shingled, seal the valley with roofing cement along the centerline where the two sets of shingles meet.

Common mistakes that lead to leaks

The most common mistake is installing step flashing incorrectly. Step flashing must overlap the shingles below it, not sit on top of them. If the flashing sits on top, water will run under it and into the wall. Each piece must also be nailed only to the dormer wall, not to the roof shingles, because the shingles move slightly as the roof expands and contracts with temperature changes. If the flashing is nailed to the shingles, it will tear and create gaps.

The second most common mistake is cutting shingles too close to the valley centerline. If a shingle extends into the valley, water will pool behind it and eventually leak. Cut shingles so they stop at least 1 inch away from the valley centerline, and make sure the cut is clean and straight. A ragged cut will catch water and direct it sideways instead of down the valley.

The third mistake is skipping the roofing cement in the valleys. Roofing cement is not waterproof by itself, but it seals the gaps between shingles and flashing where water can seep through. Without it, water will find its way under the shingles within a few years, especially on the north side of the roof where the sun does not dry the shingles as quickly.

Tools and materials you will need

You will need a roofing hammer or pneumatic nailer, a utility knife or circular saw, a chalk line, a tape measure, a caulk gun, and a ladder or roof brackets for safety. Wear soft-soled shoes with good grip, and use a safety harness if the roof pitch is steeper than 6:12 or if you are working alone.

Materials include shingles (order 10 percent extra for cuts and mistakes), step flashing (usually galvanized steel or aluminum), valley flashing (metal or self-adhesive), roofing cement, roofing nails (usually 1.25 inches long for asphalt shingles), and ridge cap shingles. If the dormers have walls that extend above the roof, you will also need counter-flashing and sealant to attach it to the siding.

The total material cost varies widely depending on the roof size, the pitch, the shingle quality, and whether you use metal or woven valleys. Labor costs also vary by region and by the roofer's experience. A four-dormer hip roof typically costs more than a straightforward gable roof because of the complexity and the time required to cut and fit shingles around the valleys and flashing.

Frequently Asked Questions

Can I use asphalt shingles on a hip roof with dormers?

Yes, asphalt shingles are the most common choice for hip roofs with dormers. They are affordable, durable, and straightforward to cut and fit around valleys and flashing. Make sure the shingles are rated for your roof pitch; most asphalt shingles work on pitches of 4:12 or steeper.

What is the difference between open valleys and woven valleys?

Open valleys have metal flashing running down the center, and the shingles on both sides are cut back to expose the metal. Woven valleys have shingles from both sides woven together with no metal showing. Open valleys shed water faster and are better for steep pitches and wet climates. Woven valleys look more uniform and are better for dry climates and shallow pitches.

How often do I need to reseal the valleys?

Roofing cement typically lasts 5 to 10 years before it cracks and loses its seal. Inspect the valleys every few years, especially after heavy rain or snow. If you see gaps or cracks in the cement, explore a fresh bead. This is much cheaper than fixing a leak inside the walls.

What if one of my dormers is on the north side of the roof?

North-facing dormers stay wet longer because they get less sun, so the shingles and flashing take longer to dry. Use metal valley flashing instead of woven valleys, and seal the valleys with roofing cement. Inspect the valleys more often, especially in spring and fall when there is more rain and less sun.

Do I need to hire a professional roofer for this job?

A four-dormer hip roof is a complex job that requires experience with flashing details and valley cuts. If you have roofed a straightforward gable roof before and are comfortable working at heights, you can do it yourself, but expect it to take 40 to 60 hours. If you have never roofed before, hire a professional. A leak in the valleys or flashing can cause thousands of dollars in damage to the interior walls and framing.