What does proper ridge vent installation look like?
Short answer. A properly installed ridge vent sits over a slot cut to the manufacturer's width, typically about 1 inch on each side of the peak, stops short of gable ends and wall intersections, is nailed with fasteners long enough to penetrate the deck, and is fed by enough soffit or edge intake. Most failures come from a slot that was never cut, a slot cut too wide, or no intake.
The checklist
- Slot width per instructions. A common spec is about 1 inch on each side of the ridge on truss roofs, measured beyond the ridge board on stick framed roofs. One major manufacturer caps the total opening, ridge board included, at 3 1/2 inches, and some rolled vents call for 3/4 inch per side.
- Slot stops short. Typical instructions stop the cut about 6 inches from the gable ends and about 12 inches from where a ridge meets a wall, chimney or another roof plane.
- Vent runs full length. The vent covers the whole ridge, including the uncut ends, so the line looks uniform.
- Correct nails. Nails must pass through the cap shingle and vent and fully penetrate the deck, which often means 2 1/2 to 3 inch ring shank nails. Overdriving crushes the vent and makes the ridge wavy.
- Matched cap shingles from the shingle manufacturer, at the correct exposure.
- One exhaust type. Old box vents or turbines removed and decked over, and gable vents usually closed off.
- Intake verified. Soffit vents open and baffled, or edge vents added.
Mistakes to look for
A ridge vent installed over solid decking with no slot is surprisingly common and does nothing. A slot cut past the end of the attic, over a porch or vaulted room, adds a leak path without adding ventilation. Short nails let the ridge lift during a Georgia thunderstorm.
Compare exhaust options in ridge vent vs box vents, and see how the whole system works in roof ventilation basics.