Gambrel Roof Materials Cost Calculator

This gambrel roof cost calculator estimates rafter lumber, sheathing, and roofing material cost from your building width, length, and pitch. Enter your dimensions once, and every cost range updates instantly. Materials only, no labor, no permits.

Building Width(ft)

Building Length(ft)

Lower Pitch(°)

Upper Pitch(°)

Eaves Overhang(ft)

Gable Overhang(ft)

Total Roof Area

1230 ft²

Rafter Lumber

$1002–$1639

100 pieces, 911 linear ft

Sheathing

$1204–$1935

43 sheets, 10% waste

Shingles

$369–$984

12.3 squares

Total Material Cost

$2575–$4558

Rafters + sheathing + roofing, materials only

What This Estimate Includes

This calculator covers three material categories: rafter lumber, roof sheathing, and finished roofing. It assumes 16 inch on-center rafter spacing, standard framing lumber at $1.10 to $1.80 per linear foot, 4×8 OSB or plywood sheathing at $28 to $45 per sheet with 10 percent waste, and either asphalt shingles at $30 to $80 per square or standing seam steel at $9 to $14 per square foot. It does not include labor, fasteners, underlayment, flashing, ridge caps, gusset plates, or permits. Add 60 to 120 percent on top of the material total for a fully installed price, depending on region and roof complexity.

How Rafter Count Is Estimated

Rafter pieces come from the building length, the gable overhang, and a fixed 16 inch spacing: the calculator fits as many rafter pairs as the length requires, then multiplies by four, because every truss line on a gambrel has a lower-left, lower-right, upper-left, and upper-right rafter.

pairs = ceil((L + 2g) / 1.33 ft) + 1 · pieces = pairs × 4

Each piece is priced at the average of the lower and upper rafter length, since a real order mixes both lengths. For an exact cut list with separate lower and upper counts, use the rafter length calculator.

Worked Example: 24 ft × 30 ft Gambrel

A 24 ft wide, 30 ft long gambrel at a 60° lower pitch and 15° upper pitch, with 1 ft eaves and gable overhangs, has a total roof area of 1,230 ft². That works out to 100 rafter pieces averaging 9.1 ft each, for 911 linear feet of framing lumber: $1,002 to $1,639 in materials. Sheathing needs 43 sheets with waste: $1,204 to $1,935. Asphalt shingles for 12.3 squares run $369 to $984. Total material cost: $2,575 to $4,558 for shingles, or $13,272 to $20,788 for standing seam metal on the same roof.

Cost Reference by Building Width

Half-circle method, 60° sweep angle, 20 ft building length, 1 ft eaves and gable overhang, material cost only.

Building Width	Roof Area (ft²)	Shingle Total	Metal Total
12 ft	445	$942–$1,666	$4,810–$7,535
16 ft	578	$1,214–$2,149	$6,245–$9,782
20 ft	712	$1,515–$2,678	$7,707–$12,073
24 ft	845	$1,815–$3,206	$9,169–$14,364
30 ft	1,046	$2,223–$3,932	$11,320–$17,734
40 ft	1,380	$2,960–$5,230	$14,962–$23,440

How to Use This Cost Calculator

1
Enter Building Size
Building width and length set the total roof area, which drives every material quantity below.
2
Set Both Pitches
Lower and upper pitch together fix rafter length. Steeper lower pitches use more rafter and roofing material per square foot of floor area.
3
Add Overhangs
Eaves and gable overhang both add directly to the roofing and sheathing area, so include them for an accurate total.
4
Pick a Roofing Type
Switch between asphalt shingle and standing seam metal to compare material cost side by side.

Budgeting Tip

Budget for standing seam metal from the start if the building will be finished living space, even though the sticker price is four to five times higher than shingles. The knuckle is the roof's weakest point for leaks, and re-roofing that transition after a shingle failure costs more over 20 years than paying for the metal once. For an outbuilding or barn where a shingle re-roof in 20 to 30 years is an acceptable cost, shingles remain the practical choice.

Frequently Asked Questions

›How much does it cost to build a gambrel roof?

Materials for a mid-size gambrel, around 24 ft by 30 ft with asphalt shingles, typically run $2,500 to $4,600. The same roof in standing seam metal runs $13,000 to $21,000 in materials. Labor usually adds 60 to 120 percent on top of materials for a professional install.

›What drives the cost of a gambrel roof up compared to a gable?

Two rafter breaks instead of one. A gambrel needs both lower and upper rafters, a gusset or purlin at every knuckle, and more roofing material per square foot of floor area than a gable of the same width. Framing labor runs higher too, because every rafter has an extra cut.

›Does this calculator include labor cost?

No. This estimate covers materials only: rafter lumber, sheathing, and roofing. Installed labor for a gambrel typically adds 60 to 120 percent on top of the material total, and varies by region, roof pitch, and whether the crew needs scaffolding for the steep lower slope.

›Is metal roofing worth the extra cost on a gambrel?

Often yes, because the pitch transition at the knuckle is the roof's most common leak point, and standing seam metal seals that transition with a continuous panel run rather than a shingle course that has to be cut and layered. Metal costs 4 to 5 times more in materials but lasts 40 to 70 years against 20 to 30 for asphalt.