Roof Layout Formula

We included a roof pitch chart below the 7 12 example image and the calculator below that.

Roof layout formula.

Which is equal to 1 4 or 1 3 the total span of the building not counting any overhang. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. Minus ridge thickness to allow for ridge becoming pole plate roof peak will be slightly higher ridge thick must be same. 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 overhang is 320 13 inches. Roof volume top of wall plate to under rafters 1346 75 ft top of wall plate to top of rafters 1868 05 ft. Enter the extension wall length into wall length and double the extension wall width then minus ridge thickness into the wall width entries.

Outside top plate edge to ridge top edge common 10 11 3 4. Porch roof extensions for hip roof porch extensions from an existing building wall you can use half the calculator results. A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally. Pitch for a gable roof the most common is generally 1 4 or 1 3.

End frieze block bird block plumb angle 20 5 side angle 41 blocks perpendicular to roof angle purlin lip cut angle 11 4. Roof pitch roof pitch is the measurement of a roof s vertical rise divided by its horizontal run. It is often compared to slope but is not exactly the same. Overhang the overhang should be measured from the outer edge of the exterior wall to the furthest point of the rafter.

The truss is a framework consisting of rafters posts and struts which supports your roof. Having the correct pitch is important. Here the number is 941 86 inches. 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.

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. 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. Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs. For instance a 4 12 pitch denotes a roof rising 4 inches for each 12 inches.