Hip vs gable roof

Same footprint, same pitch, same squares

The first thing a homeowner gets wrong about a hip roof is the size. It looks bigger from the street, so it must be more roof. It is not. Put a gable and a hip over the same rectangle at the same pitch and every square foot of plan is covered by roof sloping at that pitch, so both come out at plan area times the same slope multiplier. The hip swaps the gable’s two big rectangles for two trapezoids and two triangles, and the totals match to the square foot.

On our 40 × 30 ft example at 6/12 the multiplier is 1.118, so both shapes measure 1,342 sq ft, or 13.4 squares, before waste. You can check it section by section on the roof area calculator, and get the multiplier for any other slope from the roof pitch calculator. The rule only holds when all four hip planes share one pitch; a hip with steeper end planes has to be measured plane by plane.

So the shape never changes the area line on a bid. It changes everything around it: the waste, the linear feet of cap and metal, the edges that need starter, the framing, and what the wall below the roof has to be.

The worked takeoff, side by side

Here is the same house taken off both ways. Ridge runs along the 40 ft side on the gable; on the hip it shrinks to length minus width, because each end plane eats half the width at each end. Hips are measured with the hip factor, which is the common-rafter multiplier’s cousin for a line that runs diagonally across the plan.

The hip orders 0.7 more squares on the same area, needs 60 more feet of hip and ridge cap, and has 60 more feet of eave to start. The gable gives some of that back: 67 ft of rake trim and 225 sq ft of gable-end wall to side, paint and, in high-wind zones, brace. Put the order squares through the roof square calculator and the cap and eave footage through the shingle bundle calculator to turn this into a material list.

Where the hip spends its extra money

Every hip line is a cut line. Shingles coming across each plane get trimmed along both sides of every hip, and the offcuts are mostly too small to start the next course. A straight gable cuts only at the rakes, and those cuts are square. That is why our waste table carries 10% for a simple gable with few penetrations and 15% once hips and a valley or two show up. A cut-up hip with dormers belongs in the 18% bracket.

The labour follows the cuts. Four hips mean four lines to snap, four sets of cuts per course, and 100 ft of cap laid one piece at a time, against a single 40 ft ridge on the gable. The framing is where the gap is widest. A gable is common rafters or trusses with one cut pattern repeated down the house. A hip needs hip rafters, then jack rafters that get shorter toward each corner, each with a compound cut where it lands on the hip. Work those lengths out with the rafter length calculator before you price the frame.

Eaves, rakes and the drip edge

A hip is all eave. Every edge runs level, so every edge gets starter strip, gutters and drip edge installed the eave way: metal first, underlayment over it. A gable splits its edges: 80 ft of eave done that way and 67 ft of sloping rake where the order flips and the drip edge goes over the underlayment. The code asks for drip edge on both, lapped at least 2 in at joints, and the drip edge installation guide covers both sequences.

The totals land close (147 ft against 140 ft here), but the gutter run does not: the hip carries gutter on all 140 ft of edge, the gable on 80. Price the gutters separately, not as a share of the roof.

Wind: why the hip earns its premium on the coast

A gable end is a flat wall standing up into the wind, and the roof edge above it is a lifting surface. A hip has no such wall: every side slopes back from the wind and the planes brace one another at the hips. The Department of Energy’s Building America guide, citing wind-tunnel studies, puts the peak wind pressures on a hip as much as 50% lower than on a gable, all else being equal, and calls the hip the better choice for high-wind regions.

That does not make a gable a bad roof. It makes the gable end a detail you have to finish. The same guide, working from the IBHS FORTIFIED standards, calls for bracing gable end walls more than 3 to 4 ft tall and for structural sheathing on the gable’s vertical face: at least 3/8 in under FORTIFIED High Wind and 7/16 in under FORTIFIED Hurricane. On our example each gable end is 7.5 ft tall at the peak, so both ends are in scope wherever the program applies.

Some insurers credit roof shape on a wind-mitigation inspection, but the DOE guide notes the hip has to cover more than 90% of the house to qualify, so a hip house with gable wings may not count. After a storm, the storm damage inspection guide shows what to walk on each: rakes and gable ends on one, the long runs of hip and ridge cap on the other.

Attic space and ventilation

A gable leaves a full-length attic with headroom down the middle and two end walls you can put a louver or a window in. A hip slopes in from all four sides, so the usable attic shrinks toward the ends and there is no wall to vent through. The DOE guide puts it the same way: lots of storage and easy venting on the gable, less storage on the hip.

Ventilation is where the short ridge matters to an estimator. At the code’s 1/300 ratio, a 1,000 sq ft attic floor needs 480 sq in of net free area, and 40 to 50% of it, 192 to 240 sq in, has to sit high, no more than 3 ft below the ridge. The gable has 40 ft of ridge to spread that along. Our hip has 10 ft. Multiply the ridge vent’s rated net free area per foot by the ridge you actually have, and when it comes up short the balance goes into box vents or hip vents near the top. Run the numbers on the attic ventilation calculator and see ridge vent vs box vent for the trade-off.

What the shape does to the price

Fixr sums it up plainly: the hip is “more difficult and costly to execute than the simple gable roof.” On a re-roof the area is identical, so the difference comes from the lines in the table above: more waste, more cap, more eave, and more hours of cutting. On new construction add the framing: hip and jack rafters cost more labour per square foot of roof than repeated commons or a set of gable trusses.

The gable claws some of it back only where the gable end itself costs money: siding and paint on the triangle, a louver, and bracing and sheathing where the wind map demands it. Inland, on a simple house, the gable is the cheaper roof almost every time. On the coast the hip’s premium buys wind performance and, often, an insurance credit, and that is a trade a homeowner should see on paper. Price both on the roof replacement cost calculator using each shape’s order squares, not the bare area.