What is a gable roof?

A gable roof is a type of roof design that features two sloping sides that meet at a peak, forming a triangular shape at each end.

What does a 4/12 pitch mean?

A 4/12 pitch indicates that for every 12 horizontal inches, the roof rises 4 inches, resulting in a slope that is relatively gentle.

How do I calculate the rise for a 24 ft span with a 4/12 pitch?

To calculate the rise, you can use the formula: Rise = (Span / 2) * (Pitch Rise / Pitch Run). For a 24 ft span, the rise would be 4 ft.

A plumb cut is the cut made at the top of a rafter that allows it to sit vertically against the ridge board, ensuring a secure and stable connection.

Why is snow load not sized in this context?

Snow load considerations can vary significantly based on geographic location and specific building codes, so it's essential to consult local regulations for accurate sizing.

4/12 gable rafter on a 24 ft span

Explore the essentials of gable roofs with a 4/12 pitch over a 24 ft span. Learn about the multiplier, plumb cut, and considerations for snow load sizing.

Formula SSC-2026.1

4.00 / 12 · 18.43°

Pitch angle

18.43°

Multiplier 1.0541

Common rafter

13 ft 7 5/8 in

Tail 1 ft 5/8 in

Cuts

18.43° plumb

71.57° seat

Roof area

709 ft²

7.09 squares

Shingle bundles

3 bundles per square + 10% waste

Sheathing / felt

25 sheets

2 underlayment rolls

Delivery weight

2,886 lb

1,309 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	7.09 squares	10%	24 bundles	USD	$1,008.00	Source Spec Material / Tool
4x8 CDX sheathing	22.2 sheets	10%	25 sheets	USD	$700.00	Source Spec Material / Tool
Underlayment rolls	709 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
4.0/12	18.43°	1.054	13 ft 7 5/8 in	7.09	24	25
6.0/12	26.57°	1.118	14 ft 5 9/16 in	7.52	25	26

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: 4/12 gable rafter on a 24 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 4/12 pitch means that for every 12 horizontal units, the roof rises 4 vertical units. This ratio is crucial for determining the roof's slope and overall design.

The multiplier is used to calculate the total rise of the roof based on the span and pitch. For a 24 ft span, the rise can be calculated using the pitch ratio, which helps in determining the length of the rafters and the necessary cuts. The plumb cut refers to the cut made at the top of the rafter, which is essential for ensuring a proper fit against the ridge board.

Code reference

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

Field questions

What is a gable roof?: A gable roof is a type of roof design that features two sloping sides that meet at a peak, forming a triangular shape at each end.
What does a 4/12 pitch mean?: A 4/12 pitch indicates that for every 12 horizontal inches, the roof rises 4 inches, resulting in a slope that is relatively gentle.
How do I calculate the rise for a 24 ft span with a 4/12 pitch?: To calculate the rise, you can use the formula: Rise = (Span / 2) * (Pitch Rise / Pitch Run). For a 24 ft span, the rise would be 4 ft.
What is a plumb cut?: A plumb cut is the cut made at the top of a rafter that allows it to sit vertically against the ridge board, ensuring a secure and stable connection.
Why is snow load not sized in this context?: Snow load considerations can vary significantly based on geographic location and specific building codes, so it's essential to consult local regulations for accurate sizing.