Valleys, Hips, Ridges, and Penetration Flashing Integration

Valleys, Hips, Ridges, and Penetration Flashing Integration

Every asphalt shingle roof has features where two planes meet or where a pipe, vent, or other object breaks through the deck. These intersections are the most likely leak points on any roof. Executing them correctly is a core competency tested by NCCER and demanded by every roofing employer.

Valley Methods

A valley is formed where two sloping roof planes meet and direct water toward a single low point. Three accepted methods exist.

Open Valley. Metal valley flashing — typically W-metal or V-metal — is installed first, over an underlayment layer, with the center rib facing up. Shingles are cut back from both sides of the valley centerline, leaving an exposed strip of metal that widens slightly toward the eave to handle increasing water volume. Chalk lines are snapped on both sides to guide cuts; the gap at the top is typically 6 inches total (3 inches each side), widening by about 1/8 inch per foot toward the eave. Cut edges must be trimmed clean, embedded in roofing cement, and must not be notched or bent into the valley channel. The open metal channel is visible from the ground.

Closed-Cut Valley. No separate metal is required, though an underlayment strip in the valley is still good practice. Shingles from one plane are run past the centerline by at least 12 inches. Shingles from the intersecting plane are then laid over them, and a chalk line is snapped 2 inches off center (toward the first plane). The upper layer is cut cleanly along that line. The cut edge is embedded in a 3-inch-wide band of roofing cement. This method produces a clean diagonal cut visible at the valley.

Woven Valley. Shingles from both planes are applied alternately, each course woven over the other with no cuts at the valley. Each shingle must extend at least 12 inches past the centerline. Woven valleys require that both intersecting planes be shingled simultaneously. This method is not recommended by some manufacturers for laminated (architectural) shingles because the layering can create high spots; always check the shingle manufacturer's instructions before choosing this method.

Hips and Ridges

Hip lines and ridge lines are exposed upper edges where two planes meet. They take the most weather exposure on the roof and must be capped with purpose-built product.

Manufactured Ridge Cap Shingles. Most manufacturers supply pre-cut hip-and-ridge cap shingles sized for correct exposure. Begin at the eave end of each hip run and work upward. Nail each cap piece above the exposure line so fasteners are covered by the next course — typically two nails per cap piece, one on each side, placed to be overlapped. Maintain consistent exposure throughout; standard exposure for most manufactured caps is 5 to 6 inches, but always verify with the product data sheet. Finish hips before capping the ridge. At the ridge, begin at the end opposite the prevailing wind direction so laps face away from the wind. The final cap piece is face-nailed and the nail heads are covered with a dab of compatible sealant.

Pipe Boot (Penetration Flashing)

A pre-formed rubber boot flashing seals the gap around a pipe penetration. The rubber collar conforms to the pipe; the flat metal or plastic flange integrates with the surrounding shingles.

Installation sequence:

1. Lay field shingles up to the pipe. Cut the course that would overlap the pipe to fit around it, keeping the cut as close to the pipe diameter as practical.

2. Slide the boot over the pipe from above. The flange must lie flat on the deck.

3. The downslope portion of the flange laps over the shingles below it. The upslope portion tucks under the shingles above it. Side flanges are integrated with adjacent courses like step flashing — downslope edges exposed, upslope edges covered.

4. Nail the flange to the deck with roofing nails at the perimeter of the flange. Do not nail through the center of the flange.

5. Apply compatible sealant (specified by the boot manufacturer) around the pipe collar where the rubber meets the pipe. Ensure full coverage with no voids.

Never substitute an incompatible sealant — some petroleum-based products degrade EPDM rubber boots.

Safety

This lesson involves work on sloped mock sections that simulate real roof conditions. Even at low height, the hazards are real.

• Fall protection: Wear your harness and attach to an anchor point whenever working on a sloped section above 6 feet, per OSHA fall protection requirements. On mock sections at floor level, maintain three points of contact when moving.
• Cutting tools: Utility knives must be retracted when not in use. Snips produce sharp metal edges — wear cut-resistant gloves when handling valley metal.
• Pneumatic nailers: Keep the nose pointed at the work surface only. Never defeat the contact safety tip. Disconnect the air supply before clearing a jam.
• Sealants: Work in ventilated space. Review the SDS for the specific sealant in use before opening the tube.
• Housekeeping: Scrap metal edges and shingle cutoffs on the deck are slip and cut hazards. Clear them continuously.

Field Log Requirement

For each valley method you replicate, photograph the finished section, then record in your field log: the chalk-line offset dimension from centerline, the cut method used, and any manufacturer note that applies. This documentation habit mirrors what journeymen do on the job and directly supports your NCCER portfolio evidence.