Roof Layout Formula

H b x tan α 2 common rafters b 2 x cos α hip rafters h 2 b 2 2 hip roof area 2 x common rafters x roof base length where h roof rise b roof base width α roof pitch tan tangent cos cosine.

Roof layout formula.

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. If this isn t practical then perform the same measurement on the underside of the roof. Here the number is 941 86 inches. Roof volume top of wall plate to under rafters 1346 75 ft top of wall plate to top of rafters 1868 05 ft.

Roof pitch roof pitch is the measurement of a roof s vertical rise divided by its horizontal run. Having the correct pitch is important. Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.

Overhang the overhang should be measured from the outer edge of the exterior wall to the furthest point of the rafter. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. In the united states a run of 12 inches 1 foot is used and pitch is measured as the rise of the roof over 12 inches. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs.

End frieze block bird block plumb angle 20 5 side angle 41 blocks perpendicular to roof angle purlin lip cut angle 11 4. The important point to keep in mind when you use your truss calculator is that every truss calculation is completely unique and is based on the size of your roof and its specific dimensions. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. For instance a 4 12 pitch denotes a roof rising 4 inches for each 12 inches.

Enter the extension wall length into wall length and double the extension wall width then minus ridge thickness into the wall width entries. Porch roof extensions for hip roof porch extensions from an existing building wall you can use half the calculator results. Minus ridge thickness to allow for ridge becoming pole plate roof peak will be slightly higher ridge thick must be same. We included a roof pitch chart below the 7 12 example image and the calculator below that.

Here the overhang is 320 13 inches. Outside top plate edge to ridge top edge common 10 11 3 4. Which is equal to 1 4 or 1 3 the total span of the building not counting any overhang. Pitch also has its own denotation determined by the rise in inches in 12 inches.