A gable roof and a hip roof do not take ridge cap the same way. The shape changes which runs get capped, which runs you measure, where the first cap goes, and how the pieces meet at junctions. Match the method to the shape before you measure, or the order will count the wrong runs.
Which ridge cap method fits your roof shape?
Three things change with the shape. The run list, which is the set of lines on the roof that get capped and therefore measured. The start point of each run. The product or junction treatment. This table maps each common shape.
| Roof shape | Runs to cap and measure | Where to start | Junction or product note |
|---|---|---|---|
| Gable | The ridge run only, measured end to end along the peak | The end opposite the prevailing wind | One straight run; no angled hip cuts |
| Hip | The ridge run plus every hip run, each measured separately | Hips at the eave; the ridge at the end opposite the prevailing wind | Trim the first hip piece so its corners do not reach the gutter; keep junctions clean cut with no humps |
| Shed, single slope | The top edge only | The end opposite the prevailing wind | The first cap overhangs the end by 1/2 in |
| Gambrel | The peak ridge; the gable ends are vertical, so there are no hips | The end opposite the prevailing wind | The break between the two slopes takes flashing or bent shingles, not a cap run |
| Mansard | The hip runs; the usual form has no ridge | Hips at the eave | Caps run the full hip length across the slope break |
| Metal roof, any shape | The same runs the shape requires | Per the panel manufacturer's trim detail | A profile-matched cap with closure strips and 6 in laps |
How does the shape change the order math?
Use one named product and stated fixtures so every number checks. The product is GAF TimberTex: 30 pieces per bundle, 8 in exposure, 20 lin ft per bundle. The fixture lengths and allowances are assumptions for this article, not recommendations for any project.
Gable: 36 x 1.10 = 39.6 lin ft; bundles = ceil(39.6 / 20) = 2
A 36 ft gable ridge with a 10% allowance gives 39.6 lin ft, which rounds up to 2 bundles. The gable shape needs little beyond end cuts, so the ordering guide fits 10%.
Hip: 118 x 1.15 = 135.7 lin ft; bundles = ceil(135.7 / 20) = 7
A hip roof with a 30 ft ridge and four 22 ft hip runs measures 30 + 4 x 22 = 118 lin ft. A 15% allowance fits the angled cuts on the four hips. The order is 135.7 lin ft, which rounds up to 7 bundles.
Shed: 24 x 1.10 = 26.4 lin ft; bundles = ceil(26.4 / 20) = 2
A 24 ft top edge with a 10% allowance gives 26.4 lin ft, which rounds up to 2 bundles. As a piece check, 26.4 lin ft at 8 in exposure needs ceil(26.4 / (2/3)) = 40 pieces, and two bundles hold 60.
The same product and the same price per bundle give 2, 7, or 2 bundles across the three fixtures. The shape sets the measured runs before any allowance or rounding.
What does installation require for each shape?
Gable roof
Start at the ridge end opposite the prevailing wind. IKO, GAF, and the Canadian Roofing Contractors Association all give this rule, and the wind laps then shed water correctly.
Hip roof
Start each hip at the eave. IKO trims the first piece so the corners of the hip shingles do not extend into the gutter. Run the ridge caps from the end opposite the prevailing wind. Keep every nail covered by the next piece; the Canadian Roofing Contractors Association calls for no exposed nails and asks for any ridge junction to be clean cut and free of humps.
Dormers on a cross-gable roof
Measure each dormer ridge as its own run. Bring the dormer ridge into the main slope so the caps lap in the direction water sheds, per the Canadian Roofing Contractors Association.
Shed roof
Cap the top edge with preformed caps. One contractor-planning source starts opposite the prevailing wind, overhangs the first cap 1/2 in past the end, places two nails 1 in from the side edges, and holds 5 to 6 in of exposure. Those figures are unattributed planning conventions, so check them against the product's installation sheet.
Gambrel roof
Cap the peak with bent square shingles, as DIY installation guides describe. The break between the steep lower slope and the shallow upper slope is not a cap run. Guides treat it with shingles bent over the transition or with flashing at the joint. Those guides are unattributed DIY sources, so confirm the break detail with the shingle manufacturer's directions.
Mansard roof
A mansard is a four-sided double-slope hip roof with no gables. It has hip runs and no ridge, so the caps run the full hip length from eave to top, across the slope break.
Metal roof
The runs follow the roof shape, but the product changes. A metal ridge cap must match the panel profile from the same manufacturer. One contractor guide runs chalk lines on both sides of the peak, sets outside closure strips over sealant tape, laps each piece 6 in, and overhangs the gable trim 1/2 in. That guide is unattributed, so the panel manufacturer's trim detail controls the real order.
Cold air stiffens asphalt caps on every shape. IKO and GAF both instruct crews to warm the caps before bending them over the joint in cold weather.
When does a roof take no ridge cap?
A flat or low-slope roof has no ridge or hip lines, so there is nothing to cap. The same is true of the flat deck that closes the top of a mansard. Do not measure or order caps for a line that does not exist.
What shape errors survive the checklist?
The companion ridge cap mistakes checklist shows the bundle shortfall each error causes on a hip roof. The two errors this shape guide adds are treating a gambrel slope break as a cap run and ordering caps for a flat top that has no ridge.
Sources and scope
- IKO, Hip and Ridge Cap Shingles: From Style to Installation (published 2023-07-04, updated 2026-02-25): 2 in nails, warming in cold weather, chalk lines, hips start at the bottom with a trimmed first piece, gable ridge starts opposite the prevailing wind. Manufacturer. Verified live and accessed 2026-10-19.
- Canadian Roofing Contractors Association, 9.4.5 Ridges: start hips at eaves, ridges at the end away from the prevailing wind, no exposed nails, ridge exposure matches field exposure, junctions clean cut and free of humps, dormer ridge brought to the main slope. Trade association. Verified live and accessed 2026-10-19.
- GAF, All about Hip and Ridge Cap Shingles: the 20 to 33 lineal feet per bundle coverage range, the two-nail placement rule, the start position, warming caps in cold weather. Manufacturer. Verified live and accessed 2026-10-19.
- GAF, Seal-A-Ridge Sell Sheet, RESHR112-1124 (dated 01/2025): 45 pieces per bundle, 6 2/3 in exposure, 25 lineal feet per bundle. Manufacturer. Accessed 2026-10-19.
- Home Depot product listing quoting GAF TimberTex specifications: 30 pieces per bundle, 8 in exposure, 20 lineal feet per bundle. Retailer quoting the manufacturer. Accessed 2026-10-19.
- EngineerFix, How to Finish the Top Edge of a Shed Roof: asphalt caps on the top edge, 1/2 in end overhang, two nails 1 in from the side edges, 5 to 6 in exposure. Contractor-planning source; figures unattributed. Accessed 2026-10-19.
- DoItYourself.com, How to Add Asphalt Shingles to a Gambrel Roof: bend square shingles as ridge caps along the peak, flashing at the transitions. DIY guide; unattributed. Accessed 2026-10-19.
- Metal Roofing Source, How to Install a Ridge Cap of a Metal Roof: chalk lines, closure strips over sealant tape, 6 in laps, 1/2 in gable overhang. Contractor guide; unattributed. Accessed 2026-10-19.
Scope: installation direction, nail length, and cold-weather rules come from the manufacturer and trade-association sources listed. Shape-specific installation figures for shed, gambrel, and metal roofs come from unattributed contractor or DIY sources and serve as planning conventions; the shingle or panel manufacturer's directions control the real installation. The fixture arithmetic is derived planning math, not a manufacturer statement. Quantity planning does not certify wind or warranty terms, and roof work needs the crew's fall protection plan and the manufacturer's instructions.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, measure with the ridge cap measuring guide, lock the product with the ridge cap product guide, build the order with the ridge cap ordering guide, or check the numbers against the ridge cap worked example. The Roofing Quantity Planning hub holds the rest of the roofing set.
