How do you install vented ridge cap shingles over a ridge vent?
Short answer. After the slot is cut and the ridge vent is nailed down, cap shingles are installed over it starting at the end opposite the prevailing wind, each one overlapping the last at the exposure printed on the bundle. They are nailed with longer nails that reach through the vent into the deck, and the final cap at the far end is face nailed and sealed.
Choosing the caps
- Use the hip and ridge shingles made to match your field shingles. Many manufacturers require their own caps for enhanced warranty coverage.
- High profile caps look sharper over a vent; low profile caps look flatter.
- Cutting 3-tab shingles into caps is not appropriate for most architectural roofs.
Installation steps
- Confirm the vent: it should be centered on the slot, joined tightly, with end plugs at each end.
- Pick the direction: start at the end of the ridge opposite the prevailing wind, so the exposed edges face downwind.
- Set the first cap: at the end, aligned with the rake or ending point, nailed at the marked nailing points on each side.
- Work along the ridge: lap each cap over the previous one at the stated exposure, keeping the line straight with a chalk line.
- Nail correctly: nails go through the cap and vent and penetrate at least 3/4 inch into the deck or through it, set flush without crushing the vent.
- Finish: trim the final cap to fit, face nail it, and cover the nail heads with roofing sealant.
Mistakes that cause leaks or blow offs
- Short nails that only grab the vent.
- Overdriven nails that dimple the cap and crush the vent.
- Exposure stretched to save material.
- Installing in cold weather without hand sealing, so caps do not bond until summer.
See architectural vs 3-tab shingles and wind damage to roofs in Georgia.