Topic: Roof Framing

The Fractional Step for a regular Hip/Valley Rafters.

The Fractional Step for a Hip/Valley rafters deals with using the step-off method for laying out roof rafters. This is figured as the 45° diagonal distance of the fractional step. This differs from the fractional step of a common rafter which is just measured by the amount of the fractional step. This means that if you have a fractional step of 3-1/2" on an 8/12 roof, you need the "diagonal" measurement of a square with 3-1/2" sides.

You could take the time to "draw" out the square and then measure the diagonal or use a calculator to find the answer, but there is a quicker way.

The way to determine this is just to measure from 3-1/2" on the inside of the tongue to 3-1/2" on the inside of the body with your tape. Then using that measurement of 4-15/16", measure perpendicular from the tongue back towards the rafter tail and slide the square to that position and make your line.

 

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