Ridge Vent and Ridge Cap Repair

Purpose

A ridge vent is a ventilation component wearing a roof cap. Repair it as a cap and you get a tidy ridge over an attic that no longer breathes. This procedure guarantees the airway is open end to end when the crew leaves, that fasteners are long enough to reach the deck through the added thickness, and that an intake problem gets written down instead of buried under new caps.

The failure this prevents is the ridge that looks perfect from the driveway while the attic runs hot, the sheathing delaminates from underneath, and nobody connects the two for five years.

Scope

Covers repair and partial replacement of shingle-over ridge vent and ridge cap shingles on steep-slope asphalt shingle roofs, residential and small commercial: net free area, slot condition, end treatment, fastener length, and airway verification.

Does not cover the full attic ventilation assessment, which its own SOP owns and which this procedure calls into. Does not cover powered attic ventilators, gable louvres or bath fan terminations, or cutting a ridge slot on a roof that never had one, which is a framing and design decision.

Roles and responsibilities

Exhaust without intake is not ventilation

A ridge vent publishes a net free ventilating area, usually in square inches per linear foot on the product data sheet, and the number varies by product. Multiply it by the net vented length - total ridge minus the end sections you block off - and that is your exhaust. It only means something against the intake below, because air leaving at the ridge comes from somewhere: where soffit intake is short or blocked, the ridge draws from a gable louvre, from the far end of the same ridge, or from the house itself through ceiling penetrations.

The code sets the required total. In the edition your jurisdiction has adopted, the IRC's attic ventilation section sets minimum net free ventilating area as a fraction of the vented area, with a reduction permitted where the required area is balanced between upper and lower portions inside a stated band, commonly 40 to 50 percent in the upper portion, and where the other conditions on that reduction are met. Pull the section rather than working from memory. The practical rule that falls out is that when exhaust exceeds intake the answer is more intake, never more ridge; the assessment method belongs to the attic ventilation assessment SOP, and what this procedure owns is the comparison and the decision it forces.

Procedure

1. Set access and fall protection at the ridge, and check the wind. Access runs under the ladder setup standard and the fall protection setup SOP, with the anchor set so nobody has to stand on the ridge to reach it. Acceptance: anchorage set, everyone connected, and a measured or forecast wind speed the crew has agreed is workable for handling vent sections. Wrong looks like a tech straddling a ridge with a 4 ft section of vent in both hands. Stop rule: rising wind stops ridge work and the open ridge is covered before anyone comes down. Hazard: the ridge is the most exposed line on the building, a vent section is a sail, and the fall protection duty triggers at 6 ft under 29 CFR 1926.501(b)(13) with arrest criteria at 1926.502(d).

2. Read the whole ridge, not the damaged section. Walk the full length and inspect caps, vent body, connectors between sections, end plugs, and every exposed fastener head. Acceptance: a condition note for the full ridge length with the damaged run marked in linear feet, plus the count of missing or backed-out fasteners. Wrong looks like a scope written on the 8 ft the customer photographed. Stop rule: exposed fastener heads or open connector joints outside the damaged run get added to the scope now, because coming back for them costs another setup. Hazard: caps that lifted in wind are usually loose beyond the visible damage, so nothing is used as a handhold and nobody kneels on a cap that has not been checked.

3. Compare exhaust against intake before quoting any additional vent. Read the vent product's published net free area per linear foot, multiply by the net vented length, then measure the intake actually available at the soffits from inside the attic. Acceptance: an exhaust figure in square inches, an effective intake figure in square inches, and both written next to the code-required total for this attic. Wrong looks like a crew adding 10 ft of ridge because the attic feels hot. Stop rule: where effective intake is below exhaust, no ridge length is added on this visit - the intake finding is written as its own recommendation and quoted separately. Hazard: attic work means joists only for footing, insulation hiding wiring and framing, and heat that builds fast, so plank across the joists, carry a light, and set a turnaround time before going in.

4. Remove the damaged vent and caps, and check the slot. Take the caps and vent off the damaged run, then measure the slot against the width the vent instructions state, usually as a dimension each side of the ridge board. Acceptance: slot measured at three points along the removed run, compared to the stated dimension, deck edges sound. Wrong looks like a new vent set over a slot that was never cut wide enough. Stop rule: a narrow slot stops installation until corrected, and a slot that would need cutting into the ridge board or a structural beam stops the job and goes to a framer. Hazard: cutting sheathing releases wood dust, an inhalation route, so use dust extraction or work upwind with respiratory protection under a written program per 29 CFR 1926.103, set blade depth to the sheathing thickness only, and expect offcuts to drop into the attic for someone to retrieve.

5. Cover the open ridge whenever it is unattended, and count the covers. Any open slot left while the crew is off the roof, at lunch or overnight, gets a secured cover, and the count goes in the notes. Acceptance: a written count of covers placed, and the open length never left uncovered. Wrong looks like an open ridge and a weather forecast nobody checked. Stop rule: no cover available means the ridge is not opened further today. Hazard: an open ridge slot is a direct path into the attic for rain and wind-driven debris, and the cover is also what stops a dropped tool going through onto a ceiling below, so it is secured rather than laid on.

6. Set the vent, the end plugs and the connectors per the instructions. Install sections with the connectors the manufacturer supplies, plug both ends of the run, and fasten with a length that passes through cap, vent flange and sheathing to the penetration the shingle instructions require. Acceptance: end plugs at both ends and at any hip intersection, connectors seated, fastener length verified by adding cap thickness plus flange height plus sheathing thickness plus required penetration, no fastener spinning. Wrong looks like a standard roofing nail through the added thickness, its point short of the deck. Stop rule: a fastener that will not draw tight is pulled and the length re-checked before another goes in. Hazard: driving fasteners along a ridge puts one tech's tool in line with the other slope, so nobody works opposite an operating nailer.

7. Cap the ridge, remove the covers, and prove the airway is open. Lay caps to the exposure the shingle instructions state, hand seal the caps at each end of the repaired run per the shingle repair and blend-in standard, remove every temporary cover and reconcile the step 5 count, then go into the attic and look for a continuous line of daylight along the slot. Acceptance: covers reconciled to zero remaining, cap exposure consistent, end caps tug-tested and holding, daylight visible along the whole opened run from below. Wrong looks like a finished ridge with a cover or a strip of packaging still lying in the slot. Stop rule: any dark section is opened and cleared before the crew leaves. Hazard: this step restores the attic's exhaust path, and the daylight check from inside is the only field evidence the function you interrupted works - a ridge that looks finished from above says nothing about what is lying in the slot.

The record this produces

A ridge entry carrying: total ridge length and the damaged run in linear feet; the vent product and its published net free area per linear foot; net vented length and the exhaust figure; the effective intake figure and how it was measured; the code-required total both were compared against; slot width at three points and the instruction it was compared to; fastener length with the stack it was derived from; caps replaced; covers placed and removed; and the daylight check result.

The estimator reads the intake figure, because that is a separate job the customer has not bought yet. The next tech reads the fastener length so nobody repeats the short-nail failure.

Worked pass: 32 ft ridge, 8 ft of cap lost to wind, 1,400 sq ft attic

Step 1: anchor set below the ridge on the leeward slope, both techs connected, wind steady. Step 2: the damaged run is 8 ft, and the walk finds two backed-out fasteners and one open connector joint outside it, both added to scope.

Step 3 fails. The vent data sheet publishes 18 sq in of net free area per linear foot. The ridge is 32 ft with 1 ft blocked at each end, so 30 net linear feet, and 30 times 18 is 540 sq in of exhaust. The attic footprint is 1,400 sq ft, so at the 1 in 300 ratio the required total is 1,400 divided by 300, or 4.67 sq ft, which is 672 sq in; the 40 to 50 percent upper-portion band on that is 269 to 336 sq in. The ridge alone is 540, or 80 percent of the required total.

Intake is worse. There is 60 linear feet of continuous vented soffit published at 9 sq in per foot, so 540 sq in nominal, but from inside the attic 40 ft of it is buried under blown insulation with no baffles, leaving 20 ft effective, or 180 sq in - one third of the exhaust. The stop rule fires: no ridge is added, and the intake work is written as its own recommendation and quoted separately, with the assessment routed to the attic ventilation assessment SOP.

The cap repair proceeds. Step 4: the vent instructions call for 1 in of slot each side of the ridge board, and the existing slot measures 1 in at all three check points, so no cutting. Step 5: one secured cover over the open 8 ft, written as one. Step 6: end plugs sound at both ends, the open connector reseated, fastener length derived from cap plus vent flange plus sheathing plus the code penetration, landing on the 2-1/2 in ring shank the vent instructions also list.

Step 7: caps at 5-5/8 in exposure over 8 ft is 96 divided by 5.625, or 17.07, so 18 caps. Two end caps hand-sealed at four spots each, eight dabs, both holding. One cover in, one out. From the attic, daylight runs the full 30 ft of slot with no dark section.

The intake number is the finding the customer needed. The cap repair was real work and it got done, but at 180 sq in of intake against 540 of exhaust the attic has been pulling make-up air from the conditioned space below, and no amount of ridge work fixes that.

References

• 29 CFR 1926.501(b)(13) and 1926.502(d), the fall protection duty and arrest criteria governing roof access for this work
• 29 CFR 1926.103 for the written respiratory protection program that any respirator used for saw dust control is worn under
• IRC Chapter 8 attic ventilation and Chapter 9 asphalt shingle fastening, in the editions your jurisdiction has adopted, for the required net free area, the balance conditions on the reduced ratio, and the fastener penetration into the deck
• The ridge vent manufacturer's data sheet and installation instructions for net free area per linear foot, slot width, connectors, end plugs and fastener length
• See related: the attic ventilation assessment SOP, the shingle repair and blend-in standard, and the wind damage reseal and hand-sealing SOP