What is a 6/12 pitch on a gable roof?

A 6/12 pitch means that for every 12 horizontal units, the roof rises 6 vertical units, creating a slope that is 26.57 degrees.

A plumb cut is the angled cut made at the top of the rafters to ensure they fit properly against the ridge board, which is crucial for the roof's structural integrity.

Why is snow load not sized in this overview?

Snow load considerations are complex and depend on various factors, including local climate and building codes, and should be evaluated separately from basic roof design.

6/12 gable rafter on a 20 ft span

Explore the essentials of gable roofs with a 6/12 pitch over a 20 ft span. Learn about the multiplier, plumb cut, and the importance of snow load considerations in your construction project.

Formula SSC-2026.1

6.00 / 12 · 26.57°

Pitch angle

26.57°

Multiplier 1.1180

Common rafter

12 ft 2 3/4 in

Tail 1 ft 1 7/16 in

Cuts

26.57° plumb

63.43° seat

Roof area

636 ft²

6.36 squares

Shingle bundles

3 bundles per square + 10% waste

Sheathing / felt

22 sheets

2 underlayment rolls

Delivery weight

2,538 lb

1,151 kg · 70 lb bundles, 46 lb sheets, 28 lb rolls

Gable truss triangleLive scaled blueprint

Rise and run are scaled from the span, overhang, and pitch. The small triangle is the pitch ratio.

Bill of materials and shopping list
Item	Net	Waste	Order	Unit price	Line total	Source Spec Material / Tool
Architectural shingle bundles	6.36 squares	10%	21 bundles	USD	$882.00	Source Spec Material / Tool
4x8 CDX sheathing	19.9 sheets	10%	22 sheets	USD	$616.00	Source Spec Material / Tool
Underlayment rolls	636 ft²	overlap allowance	2 rolls	USD	$110.00	Source Spec Material / Tool
Ridge cap bundles	26.0 ft ridge	—	2 bundles	25 ft per bundle	—	Source Spec Material / Tool

Source links open a product search on the Amazon storefront for the selected currency. SiteSpecCalc may earn a commission. The link does not change the quantities above.

Side-by-side pitch comparison
Pitch	Degrees	Multiplier	Rafter	Squares	Bundles	Sheets
6.0/12	26.57°	1.118	12 ft 2 3/4 in	6.36	21	22
8.0/12	33.69°	1.202	13 ft 1 3/4 in	6.84	23	24

Show the deterministic formula

Angle = arctan(rise ÷ 12). Multiplier = √(1 + (rise ÷ 12)²). Gable run = span ÷ 2 − ridge thickness ÷ 2. Rafter length = (run + horizontal overhang) × multiplier.

Plumb cut = pitch angle. Seat cut = 90° − pitch angle. Area uses both slopes on a gable and one slope on a shed, and it includes a rake overhang equal to the eave overhang.

Bundles = ceiling of squares × 3 × 1.10. Sheets = ceiling of area × 1.10 ÷ 32. Rolls use 360 ft² effective coverage. Delivery weight plans 70 lb per bundle, 46 lb per sheet, and 28 lb per roll, then the header converts that pound total at 1 lb = 0.45359237 kg.

Contractor sign-off

Project: 6/12 gable rafter on a 20 ft span

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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.

Engineering notes

A gable roof with a 6/12 pitch means that for every 12 horizontal units, the roof rises 6 vertical units. This ratio is crucial for determining the roof's slope and overall design. The multiplier is used in calculations to determine the area and load-bearing capacity of the roof based on its dimensions.

The plumb cut refers to the angled cut made at the top of the rafters, which allows them to fit snugly against the ridge board. Proper plumb cuts are essential for ensuring the structural integrity of the roof. It's important to note that snow load considerations should be evaluated separately, as they are not included in this basic design overview.

Code reference

Consult local building codes for specific requirements regarding roof design, including snow load calculations.

Field questions

What is a 6/12 pitch on a gable roof?: A 6/12 pitch means that for every 12 horizontal units, the roof rises 6 vertical units, creating a slope that is 26.57 degrees.
What is the purpose of the multiplier in roof calculations?: The multiplier is used to calculate the area and load-bearing capacity of the roof based on its dimensions, ensuring that it can support the expected loads.
What is a plumb cut?: A plumb cut is the angled cut made at the top of the rafters to ensure they fit properly against the ridge board, which is crucial for the roof's structural integrity.
Why is snow load not sized in this overview?: Snow load considerations are complex and depend on various factors, including local climate and building codes, and should be evaluated separately from basic roof design.