The ridge cap is the last piece of a metal roof installation and one of the most critical for weathertightness. A properly installed ridge cap seals the open peak where two roof planes meet, keeping water, birds, insects, and debris out of the structure. Installing it incorrectly — or skipping it entirely — is the most common source of metal roof leaks and pest infiltration on agricultural and residential buildings across Northern California.

What is a Metal Ridge Cap?

A metal ridge cap is an L-shaped or curved piece of formed steel sheet that bridges the ridge of a gable roof, covering the open top edges of the corrugated panels from both sides. Our 10ft 26 gauge ridge caps are available in all six panel colors to match your panels, creating a consistent, professional finish.

The ridge cap bridges the gap and creates a weather seal, but there’s still an opening: the corrugated profile of the panels leaves gaps between the panel surface and the flat underside of the ridge cap at each corrugation valley. These gaps are filled with foam closure strips during installation.

Tools and Materials

• Ridge cap sections (10ft each; measure your ridge length and add 10% for laps and trimming)
• Outside foam closure strips (pre-formed to match your corrugation profile; one per panel at the ridge)
• Butyl tape (for lap joints between cap sections)
• Roofing screws: same type used for panels (#10 or #12 self-drilling with EPDM washer)
• Cordless drill with hex driver bit
• Metal snips for trimming cap to length at gable ends
• Sealant gun with butyl caulk (for any gaps at the gable end overhangs)

Step 1: Install Outside Closure Strips

Outside closure strips are pre-formed foam pieces shaped to fit over the top corrugations of your panels, filling the gap between the panel surface and the ridge cap. They are installed at the ridge before the cap goes on.

Position the outside closure strips along the top edge of each panel row on both sides of the ridge. The closure strip profile should match your panel’s corrugation pattern — the foam peaks and valleys of the strip align with the panel’s corrugation valleys and crowns respectively, with the flat top surface ready to accept the ridge cap.

Press the closure strips firmly into position. You can use a staple or a dab of construction adhesive to hold them in place while you work, but the final fastening from the ridge cap screws will hold everything securely.

Some installers also run a bead of butyl tape along the top of the closure strip before the ridge cap is placed, to create an additional waterproof seal. This is optional in Sacramento’s climate but recommended for any installation that might see significant wind-driven rain.

Step 2: Position the Ridge Cap

Place the first ridge cap section at one gable end, with the cap overhanging the gable by approximately 1 inch. Center the cap over the ridge so it covers an equal amount of panel on each side.

For standard ridge caps with a 9–10 inch total width (4.5–5 inches per side), the cap should extend down each roof slope enough to cover the top 4–5 inches of the panels on each side. This provides adequate coverage of the closure strip and panel top edge.

Step 3: Fasten the Ridge Cap

Drive roofing screws through the ridge cap and closure strips, through the panel, and into the ridge board or top purlin beneath. Fasten at every corrugation valley on both sides of the cap — if your panel has 11 corrugations, you’ll have approximately 5–6 fastening points per side per linear foot.

Use the same EPDM-washer screws you used for the panels. The screw length needs to penetrate the ridge cap, closure strip, panel, and at least 1 inch into the supporting structure. Measure your specific assembly to choose the correct screw length.

Don’t overtorque: the EPDM washer needs to compress slightly — you should see the rubber just beginning to spread at the screw rim. Overtorquing crushes the washer and can dimple the ridge cap.

Step 4: Join Cap Sections

On ridges longer than 10 feet, you’ll need to join sections. Overlap sections by at least 6 inches, with the downslope-end section under the upslope-end section so water runs over the lap joint rather than into it.

Apply butyl tape along the upper lap surface before closing the joint. Drive screws through both sections at the overlap to secure the joint mechanically.

Step 5: Trim and Finish the Gable Ends

At each gable end, the ridge cap should overhang the rake edge by approximately 1 inch. If it overhangs more, trim with metal snips to an even 1-inch projection. Apply a dab of sealant to the cut end of the cap to seal any exposed metal at the trim point.

If there are gaps visible at the gable end of the ridge cap where the corrugation valleys aren’t filled by the closure strip (particularly if the last panel at the rake end was trimmed to a partial width), fill those gaps with outside closure strip material trimmed to fit, secured with sealant.

Common Ridge Cap Mistakes to Avoid

• No closure strips — the most common mistake; leaves open gaps that allow bird and insect entry and wind-driven rain infiltration
• Wrong closure strip profile — foam strips must match your specific corrugation profile; generic strips that don’t fit properly leave partial gaps
• Insufficient overhang at gable ends — a flush-cut ridge cap at the gable end allows water to run between the cap end and the panel, down the gable fascia
• Insufficient overlap on long ridges — a 2–3 inch overlap is not enough; 6 inches minimum with butyl tape between sections

Frequently Asked Questions

How many ridge cap sections do I need?

Measure the total ridge length in feet. Divide by 10 (one section = 10 feet). Add one section for laps and trimming. For a 30-foot ridge: 30 / 10 = 3 sections + 1 = 4 sections minimum. With 6-inch laps: 30 feet / 9.5 feet of effective coverage per section = 3.2 → 4 sections.

Can I use the same color ridge cap as my panels?

Yes — matching ridge caps are available in all six panel colors. Using a matching color creates a cohesive installation. Mixing colors (e.g., dark gray panels with white ridge cap) is also done for aesthetic contrast, but matching is more common.

What if my ridge is not perfectly straight?

Minor imperfections in ridge straightness can be accommodated by the ridge cap, which has some flexibility. For a ridge with a significant sag or bow, shim the ridge board before panel installation to straighten it; the ridge cap will follow the structural ridge regardless of minor variations.

Do I need a ridge cap on a shed-style (single-slope) roof?

No — a shed roof doesn’t have a ridge by definition. The high end of a shed roof where the panels terminate at a wall needs flashing (typically a piece of L flashing or step flashing) to seal the wall-to-roof connection, but not a ridge cap. Only gable and hip roofs that come to a peak need ridge caps.