Outil de surplomb gratuit

Calculateur de pente de toit avec surplomb

Ce calculateur de pente de toit avec surplomb calcule la longueur totale des chevrons, y compris l'extension de l'avant-toit au-delà du mur extérieur. Les surplombs résidentiels standard varient de 12 à 24 pouces (305 à 610 mm), offrant une protection contre les intempéries et de l'ombre. La calculatrice détermine la dimension complète du chevron, de la crête à la queue, l'ajout du chevron en surplomb, la profondeur du soffite, la hauteur de la planche de bord et l'angle de coupe à l'aplomb de la queue. Un calcul correct du porte-à-faux garantit une commande précise du bois et évite les dommages causés par la pluie et le soleil aux murs extérieurs et aux fondations.

expand Rafter & Overhang Diagram

WALL STRUCTURAL RAFTER FASCIA SOFFIT RIDGE 18 in
Tail Length20.1 in
Fascia Drop9.0 in
Soffit Width18 in
expand Overhang Inputs
ft
: 12
in
in
straighten Rafter + Overhang Results
Structural Rafter—
Overhang Addition—
Total Rafter Length—
Fascia Drop—
Soffit Width—
Suggested Lumber—

Comment calculer la longueur des chevrons avec surplomb

La longueur totale du chevron est égale au chevron structurel (faîte à plaque murale) plus la queue en surplomb (plaque murale à fascia). Les deux sections suivent la même pente, le calcul du surplomb utilise donc le même multiplicateur de pente que le toit principal.

tune Drag the Slider to Change Pitch
Run Rise Slope 26.57°
0.5:12 24:12
Angle 26.57°
Grade 50.0%
Multiplier 1.118
Type Conventional
1
straighten

Calculer les chevrons structurels

2
expand

Calculer l'ajout de surplomb

3
calculate

Déterminer la longueur totale des chevrons

Formules de calcul du surplomb

Formules pour la longueur des chevrons, la profondeur du soffite et les dimensions des bordures de toit avec surplomb :

straighten Chevron en surplomb
Chevrons en surplomb = Largeur du surplomb × Multiplicateur
18" × 1.118 (6:12) = 20.1" rafter addition
rotate_right Fascia Height
Fascia Drop = Overhang × (Rise ÷ 12)
18" × (6 ÷ 12) = 9" vertical fascia drop
percent Soffit Width
Soffit = Overhang Width (horizontal)
18" overhang = 18" horizontal soffit panel width
science Live Formula Calculator
ft
ft
Pitch 6 : 12
Angle 26.57°
Grade 50.0%
Rafter 13.42 ft
Multiplier 1.118

Overhang Dimensions by Pitch Chart

Click any row to see the pitch angle visualized. The chart covers all standard pitches from flat (1:12) to steep (12:12) with walkability ratings, material compatibility, and snow shedding performance.

Pitch Angle Grade Multiplier Type Walkability Snow Shedding
1:12 4.76° 8.3% 1.003 Flat/Low Easy Poor
2:12 9.46° 16.7% 1.014 Low Slope Easy Poor
3:12 14.04° 25.0% 1.031 Low Slope Easy Fair
4:12 18.43° 33.3% 1.054 Conventional Easy Fair
5:12 22.62° 41.7% 1.083 Conventional Easy Good
6:12 26.57° 50.0% 1.118 Conventional Moderate Good
7:12 30.26° 58.3% 1.158 Conventional Caution Very Good
8:12 33.69° 66.7% 1.202 Conventional Caution Very Good
9:12 36.87° 75.0% 1.250 Steep Unsafe Excellent
10:12 39.81° 83.3% 1.302 Steep Unsafe Excellent
11:12 42.51° 91.7% 1.357 Steep Unsafe Excellent
12:12 45.00° 100.0% 1.414 Steep Unsafe Excellent
6:12 — 26.57°
Compatible: All Types

FAQs

Answers to the 14 most common questions about roof pitch, slope angle, walkability, snow load, and roofing materials.

What is a standard roof overhang?

Standard residential roof overhang is 12 to 24 inches (305–610 mm). 12 inches is the minimum for weather protection. 18 inches is most common. 24 inches or more provides maximum shade and wall protection but may require additional structural support.

How do overhangs affect rafter length?

Overhangs add rafter length equal to the overhang width × pitch multiplier. An 18-inch overhang at 6:12 pitch adds 20.1 inches of rafter. At 12:12 pitch, the same overhang adds 25.5 inches. Always include overhang when ordering rafter lumber.

What is a soffit on a roof overhang?

The soffit is the horizontal underside panel that closes the gap between the fascia and the exterior wall. Soffit width equals the horizontal overhang distance. Vented soffits provide attic ventilation. The soffit is always horizontal regardless of roof pitch.

How do you cut a rafter tail for overhang?

The rafter tail cut is a plumb cut at the same angle as the main rafter plumb cut. For a 6:12 pitch, set the framing square at 6 and 12, mark the plumb line at the desired overhang distance from the bird's mouth. The tail plumb cut angle is 26.57°.

What is a bird's mouth cut?

A bird's mouth is a notch cut in the rafter where it sits on the wall top plate. It consists of a horizontal seat cut (matching the plate width) and a vertical plumb cut. The seat cut should not exceed ⅓ of the rafter depth to maintain structural integrity.

Does overhang width affect building code compliance?

Yes, overhangs wider than 24 inches may require additional engineering and may affect setback calculations. Some jurisdictions count overhangs exceeding 12–24 inches (varies by code) in the building footprint for setback measurement purposes.