What is a multiplier in roofing?

The multiplier is a factor used to calculate the total area of the roof based on its pitch. For a 10/12 pitch, this multiplier helps in determining the amount of materials needed and the overall load the roof will bear.

A plumb cut is the cut made at the top of a rafter that allows it to sit flush against the ridge board. It is essential for ensuring that the rafters are properly aligned and securely fastened.

Why is snow load not sized in this context?

Snow load sizing can vary significantly based on geographical location and specific building codes. In this context, it is important to consult local regulations to determine the appropriate snow load requirements for your gable roof.

10/12 gable rafter on a 16 ft span

Learn about gable roofs with a 10/12 pitch on a 16 ft span, including key concepts like multiplier, plumb cut, and considerations for snow load sizing.

Formula SSC-2026.1

10.00 / 12 · 39.81°

Pitch angle

39.81°

Multiplier 1.3017

Common rafter

11 ft 7 5/8 in

Tail 1 ft 3 5/8 in

Cuts

39.81° plumb

50.19° seat

Roof area

605 ft²

6.05 squares

Shingle bundles

3 bundles per square + 10% waste

Sheathing / felt

21 sheets

2 underlayment rolls

Delivery weight

2,422 lb

1,099 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	6.05 squares	10%	20 bundles	USD	$840.00	Source Spec Material / Tool
4x8 CDX sheathing	18.9 sheets	10%	21 sheets	USD	$588.00	Source Spec Material / Tool
Underlayment rolls	605 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
10.0/12	39.81°	1.302	11 ft 7 5/8 in	6.05	20	21
12.0/12	45.00°	1.414	12 ft 7 11/16 in	6.57	22	23

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: 10/12 gable rafter on a 16 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 10/12 pitch means that for every 12 horizontal units, the roof rises 10 vertical units. This steep pitch can affect various calculations, including the multiplier used for determining the total roof area and load considerations.

The plumb cut refers to the angle cut made at the top of the rafters, which is crucial for ensuring a proper fit against the ridge board. Understanding these cuts is essential for accurate framing and structural integrity.

Code reference

Consult local building codes for specific requirements regarding roof design and snow load considerations.

Field questions

What is a multiplier in roofing?: The multiplier is a factor used to calculate the total area of the roof based on its pitch. For a 10/12 pitch, this multiplier helps in determining the amount of materials needed and the overall load the roof will bear.
What is a plumb cut?: A plumb cut is the cut made at the top of a rafter that allows it to sit flush against the ridge board. It is essential for ensuring that the rafters are properly aligned and securely fastened.
Why is snow load not sized in this context?: Snow load sizing can vary significantly based on geographical location and specific building codes. In this context, it is important to consult local regulations to determine the appropriate snow load requirements for your gable roof.