How do you install architectural roof shingles correctly?
Short answer. Architectural shingles go on over a prepared deck with drip edge, underlayment, leak barrier and starter strips, then are laid from the eave up with staggered joints, the manufacturer's exposure, and nails driven flush in the marked nailing zone. Most failures trace back to a handful of mistakes, especially high nailing, skipped starter strips and reused flashing.
The order of work
- Tear off and repair the deck so it is flat, dry and solid.
- Eave drip edge on the deck, then underlayment, with leak barrier in valleys and around penetrations; rake drip edge goes over the underlayment.
- Starter strip along the eaves and usually the rakes, so the first course has a sealant line beneath it.
- First course flush with the starter, then each course at the exposure printed on the wrapper, often around 5 5/8 inches.
- Joints offset course to course by at least the minimum in the instructions, so seams never line up.
- Step flashing at walls, new pipe boots, valley treatment, then ridge vent and matching hip and ridge cap.
Five mistakes that cause trouble
- High nailing. Nails above the nailing zone miss the layer beneath, so the shingle can pull loose in wind. This is a leading cause of blow-offs.
- Overdriven or crooked nails. A nail head that cuts into the mat holds poorly. The nail gun's air pressure should drive nails flush.
- No starter strip. Using upside-down field shingles, or nothing, leaves the first course unsealed at the edge.
- Reused flashing. Old step flashing and boots are bent and aged, and new ones cost little compared with a leak.
- Wrong nail count. Very steep slopes and some warranties call for extra nails or hand sealing.
Choose a crew that follows the printed instructions, because the warranty depends on them; see roofing warranties explained and what to expect on replacement day.