Roof Trim · Metal building trim guide
Metal Roof Ridge Cap for R-Panel and PBR Roofs
Ridge cap covers the peak where the two roof slopes meet, sealing the panel ends against rain, wind and birds.
Also called: peak cap, ridge roll, ridge flashing, formed ridge, flat ridge
A metal roof ridge cap is the trim that runs along the very top of a two-sided roof, where both slopes meet. It covers the open top ends of the roof panels so rain, wind-driven water, birds and wasps cannot get in at the peak.
This guide covers what a ridge cap does, what size and color to get for R-panel or PBR, how to figure how many pieces you need, and how to install it the right way. If you are building a carport, barn, shed or shop in the Houston area, we can help you build the full trim list.
What Is a Metal Roof Ridge Cap?
A ridge cap (also called a peak cap or ridge roll) is a long piece of sheet metal bent down the middle to match the angle of your roof. It sits on top of the panels at the peak and overlaps both slopes.
It does four jobs. It keeps water out of the gap between the two rows of panels. It blocks wind from blowing rain up under the panel ends. It keeps birds, wasps and rodents from nesting in the open ribs. And it gives the roof a clean, finished line from end to end.
Where Ridge Cap Goes on a Metal Building
Ridge cap goes on any gable roof, meaning a roof with two sides that slope down from a center peak. That includes A-frame vertical-roof carports, RV covers, barns, garages and enclosed shops.
It is used when the roof panels run vertically, from the eave up to the peak. A rounded regular-style carport with panels running the long way usually has no ridge cap. A single-slope roof (lean-to or shed roof) has no ridge either; it uses high-side eave trim at the top edge instead.
Ridge Cap Sizes, Gauge, Profile and Colors
Most ridge cap for R-panel and PBR is 26 gauge, the same as the panel. Thinner 29 gauge ridge cap exists for lighter carport roofs. You can get it in bare Galvalume or in painted colors to match or contrast with your panels.
The cap must be bent to your roof pitch. A 3:12 roof needs a different bend than a 1:12 or 4:12 roof, so we always ask for the pitch before we bend or pull ridge cap. Each side of a typical R-panel ridge cap is roughly 8 to 12 inches wide, but widths vary by maker, so ask.
Pieces are typically 10 or 12 feet long. A plain flat-style cap is most common on metal buildings. Profiled and vented ridge options also exist; ask us what is available for your panel. Custom bends can be made from flat stock if you are matching an older roof.
How to Measure Ridge Cap and How Many Pieces to Order
Formula: ridge length (building length plus any gable overhang on each end) x 1.10 for laps and waste, then divide by the piece length and round UP to whole pieces. Each joint loses a few inches to the overlap, so never count on the full piece length.
Worked example: a 30 x 40 gable building with 12 ft walls and a 3:12 pitch, no gable overhang. The ridge is 40 ft. 40 x 1.10 = 44 ft. 44 / 10 ft pieces = 4.4, so order 5 pieces of ridge cap bent for 3:12. Check it: four pieces would only cover about 39 ft after three laps, which is short.
Do not forget the closures. R-panel and PBR cover 3 ft per sheet, so 40 / 3 = 13.3, call it 14 outside closures per side, 28 total.
How to Install a Metal Roof Ridge Cap
Install the ridge cap after all roof panels are on and fastened. Lay out the job so the laps face away from the prevailing wind.
- Check that the panels on both slopes stop about the same distance short of the peak and that the ribs line up across the ridge.
- Run a strip of butyl tape across the panel flats near the top of each slope, set the outside foam closures on it so they fill the ribs, then run a second strip of butyl tape on top of the closures.
- Start at the end of the building away from the prevailing wind. Set the first piece of ridge cap so it overhangs the gable end evenly and lines up straight.
- Fasten through the cap, the closure and into the panel ribs on both sides with #14 x 7/8 in. lap (stitch) screws, about one per major rib. If you want extra hold, some crews fasten into the ridge purlin with longer #12 or #14 roofing screws.
- Lap the next piece over the first by about 4 to 6 inches (practice varies) with a bead of butyl or sealant inside the lap, and stitch the lap.
- Trim the last piece to length, fold or cap the open ends at the gables if your trim style calls for it, and wipe off metal shavings so they do not rust on the paint.
Common Ridge Cap Mistakes to Avoid
- Ordering ridge cap without giving the roof pitch. A cap bent for the wrong angle will not sit flat or seal.
- Skipping the outside closures. Without them, wind blows rain right under the cap and wasps move in.
- Lapping joints into the wind, which pushes water back into the lap.
- Over-driving screws so the washer squashes out or the cap dents. Snug is enough.
- Using full 10 ft lengths in your math and coming up one piece short.
What to Order With Your Ridge Cap
Ridge cap is one part of a roof trim package. Order these at the same time so you only make one trip.
- Outside foam closures matched to your panel profile, two rows (one per side).
- Butyl tape for above and below the closures and inside the laps.
- Color-matched #14 x 7/8 in. lap or stitch screws.
- Rake trim for the sloped gable edges and eave trim or gutter for the low edges.
- Touch-up paint in your trim color.
Get Metal Roof Ridge Cap in Houston From Ironrod Steel
Ironrod Steel Co. rolls its own R-panel and PBR roofing and supplies the matching ridge cap, trim, foam closures, screws and butyl tape to go with it. Send us your building size, roof pitch and a few photos, and we will help you build the whole trim list. Pick up at 8122 Hillsboro St in Houston, or ask about delivery across Houston and Southeast Texas. Call or text (281) 902-7619.
Ridge Cap FAQ
Do I need closures under a metal roof ridge cap?
Yes, on R-panel and PBR roofs you should use outside foam closures under the ridge cap on both sides. They fill the gaps under the ribs so wind-driven rain, birds and insects stay out. Set them in butyl tape for a tight seal.
Why do you need my roof pitch to sell ridge cap?
Ridge cap is bent down the middle to match the angle of your two roof slopes. A cap made for 3:12 will not sit flat on a 1:12 or 4:12 roof, so it will gap or rock. Tell us the rise per foot, or send a photo, and we will match it.
How much should ridge cap pieces overlap?
Most crews lap ridge cap about 4 to 6 inches with butyl or sealant in the joint, but practice varies by panel maker. Always lap away from the prevailing wind so the open edge faces downwind.
Does a carport need a ridge cap?
A carport with vertical roof panels running from eave to peak needs a ridge cap. A rounded regular-style carport with horizontal panels usually does not. A single-slope carport uses high-side eave trim at the top instead.