Hip Rafter Length
Correct hip rafter length can easily be determined with the use of a Construction Master Calculator. If you enter the right information there is no need to shorten the rafter half the thickness of the ridge board.
If you deduct the thickness of the ridge board when you calculate the common rafter length then the hip length given by the calculator will be correct with no need to further shorten the hip.
Let us use as an example a building that is 24 feet by 28 feet. With a standard hip roof and a 6/12 pitch. Below is a snapshot of the paperless tape feature found on the calculator.
Paperless Tape
24. FEET – 1 1/2 INCH = 23-10 1/2 FEET INCH ÷ 2. = 11-11 1/4 FEET INCH RUN 6. INCH PTCH 13- 4 3/16 FEET INCH DIAG 17-10 7/8 FEET INCH H/V 5-11 5/8 FEET INCH RISE 16. INCH JKOC 1- 5 7/8 FEET INCH INCR 11-10 1/4 FEET INCH JK 1 10- 4 3/8 FEET INCH JK 2 |
ExplanationBuilding Width Thickness of Ridge Board Width Minus Ridge Board Divided by 2 Run of Common Rafter Pitch of Roof Common Rafter Length Hip Rafter Length Peak of Roof Above Wall Plates Jack Rafter Spacing Difference in Jack Length Longest Jack Rafter The rest of the Jack Rafters |
How to Measure Hip Rafters
Hip rafters should be measured along the top from the long point of the plumb cut.
I will often go ahead and make the plumb cuts on the hip rafter so its easier to measure and mark the seat cut and tail cut.
To find the amount to add for the tail just add the run of the overhang minus the thickness of the sub fascia. For a one foot eave with 2 x 6 fascia this would be 10 1/2 inches.
So you would add 15 3/4 inches for the tail cut.
6. INCH PTCH
10 1/2 INCH RUN
15 3/4 INCH H/V
Links to Related Carpentry Pro Framer Pages