How To Figure Out Roof Rafter Length

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.

How to figure out roof rafter length. Using the appropriate roof pitch table in a rafter cutting guide such as 4 12 determine the length of each rafter based on the correlating measurement shown for 7 feet. Use the pythagorean theorem to calculate the rafter length. Use a framing square to mark a plumb cut as close to the end of the board as possible. 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.

Determine the camber along the timbers length. If you are calculating rafter length from the center of the ridge beam as shown below you will need to subtract half of the thickness of the ridge beam from the top end of the rafter. Use our online rafter length calculator to quickly compute the length of the shed roof rafter by entering the measurements of overhead length of roof span pitch or angle. Hook the long point with a tape measure stretch it.

I prefer using the right hand side of the board for this. There is no standard universal pitch of roof. If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be added to the rafter length. Before you can mark the rafter lengths and layout check the.

Includes result for hip valley factor slope factor and the roof slope in degrees. Mark the plumb cuts. Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement. For example a roof that rises 6 inches for every 12 inches of horizontal run has a 6 12 pitch.

Divide this in half and the result is 7 feet. Marking out the roof rafter lengths onto the timber before cutting step 1. A2 x b2 c2 your rafter length 14400 20736 35136 the square root of which 187 446 your rafter length in inches step 2 lay out your rafter align your framing square so the 10 mark and 12 mark meet the edge of your rafter stock. With the tape measure hooked onto the top end transfer your two rafter lengths onto.

For example if the ridge beam is 1 5 inches thick subtract 3 4 of an inch from the overall rafter length. Place the board on a set of sawhorses with the crown away from you. Rafter length using pitch v r 2 sqrt 1 p 2 where v overhang r roof span p pitch.