Unequal Sloped Roofs

Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter.

Unequal sloped roofs.

You will have to chamfer the end of the ridge on a unequal pitched roof to keep the ridge in the roof plane alignment. The formulas below use the law of sines to calculate the unknown length or angle. Using a tape measure make a pencil mark 12 inches from the end of a carpenter s level. It is advisable to prepare a framing plan as shown in fig.

Drawing a superimposes the common rafters for the two roof pitches and illustrates the problem that occurs when roof layout starts at the outside edge of the exterior walls. Put on a pair of work gloves. Unequal pitch roof trigonometry calculating unequal pitched roofs is easy if you know what trigonometry functions to use. Where roofs of unequal pitch join it requires careful layout to create equalwidth soffits with equal height fascias.

Major pitch angle minor pitch angle major run calculate minor run minor run major run tan major pitch angle tan minor pitch angle minor run major run major pitch minor pitch known variables. Major pitch angle minor pitch angle minor run calculate. Major pitch angle minor pitch angle span plate line difference calculate major minor runs theoretical plate line span theoretical span span plate line difference tan minor pitch angle plate line difference run span theoretical span major run. The formulas below use the law of sines to calculate the unknown length or angle.

Create a roof slope using slope arrows. The correct way to calculate the minor pitch king common rafter keeping all of the roof framing members in the roof planes is to use the major and minor plan angles. Then you ll be able to measure slope from an unfinished attic space under the roof. The rafter tools app irregular hip rafter function calculates the correct king common rafter length for unequal pitched hip rafter roofs.