“ The secant” or line length ratio. That is achieved by dividing the hypotenuse of the unit rises and unit run of the pitch (9/12) by 12 inches. So in this case, 15 inches divided by 12 equals 1-1/4. 1-1/4 x16” equals 20”. 20 is the common difference of the jacks.
I gave a roof class in Aurora. That class was instigating and organized by Carpenter who attended a class in California. Unless he organizes another one I probably won’t get there again.
Winner of a video, I have been researching "pitching plate roof construction" for a while now, and I think this has helped. Ever heard of - Beybigail Nonpareil Breakthrough - (do a search on google ) ? It is a good one of a kind product for discovering how to create better sheds and improve your woodworking without the headache. Ive heard some pretty good things about it and my buddy got great results with it.
what i was taught to do. look at how the common and hip are nailed at the top think of the center of the common and the center of the hip take a common rafter lay it on edge with the bottom of the rafter facing up , so you would have the seat cut up. This rafter has been cut for the thickness of the ridge say you are cutting a 4 '' slope the distance between the jacks is 2' 1 1/4'' you are working at the bottom of the rafter let the tape stick over about7/8'' this will be where the end of the rafter would be if it had not been cut for the ridge . then measure down 2' 1 1/4'' that is the difference in length of the hip jacks on 24'' centers.. since you are working to the center of the hip you would shorten 1/2 the thickness of hip on a 45 degree angle or about 1'' 1/4 now measure back up 3/4 that is the long point of the side cut now from that mark put marks down the comm rafter 2' 1 /4 '' say you have 4 hips lay your pattern rafter on edge and put up at least 8 boards mark the seat cut on all 8 then go to the top mark the plum cuts at the mark on the comm rafter mark 4 away from you and 4 towards you then set your skill saw at 45 degrees and cut your mark then go down and with your pattern mark out the seat cut and over hang cut these on some jobs i would lay maybe 32 rafters and mark then with a long square
@@roofcuttingandstacking7925 No Sir. Came here looking for a video to teach the girls in the office how to better interview a guy who claims to be a framer. They need Framing 101. Yours is Graduate School level ;)
@@roofcuttingandstacking7925 i have a question you gave your email address before but I broke my old phone I was wondering if I could pick your brain on an upcoming project of valley roof framing thankyou for your videos and teaching you do a wonderful job of breaking things down so I understand, Bruce Rewa
Technically called the secant of the common rafter. The secant is obtained by using the square root method of the unit rises to determine the hypotenuse, then dividing it by 12. So if it was a 6/12 pitch it would be: 6 squared plus 12 squared equal, then push the square root button and divide the answer by 12 to put it in inches. That would look like 36+ 144= 180, the square root of which is 13.416. Divided by 12=1,118
@@roofcuttingandstacking7925 what's a secant? Also what about the 16 you were saying? Also wouldn't that be for a 12 inch run bigger the run bigger the number? So you devide your total rafter length by 12? Is that with or without the ridge dediluction?
I go over a whole bunch of that stuff on this channel. But essentially you take the secant and multiply it by the on center spacing to get the common difference of the Jack rafters.
I would fly to come learn from you too! Where do I sign up? I’ve learned more from mock up roofs in my garage then my framing boss ever taught me. I’d love to learn from you.
Wayne Send an email to and I am nmridgeconstruction@yahoo.com and I’ll put you on the list. They are eight hour classes, cost $200 and we build a big model , about 8’x14’
9 squared plus 12 squared =225. The square root of 225 = 15”. That is 1 foot and a part of a foot. We want to make it one inch and a part of an inch. So divide it by 12. That equals 1.25. This is the secant of a 9/12 pitch roof. It is also known as the Line Length Ratio to us framers. Multiple it by the on center spacing of the rafters and it gives the common difference of the jack rafters. 1.25x16”on center equals 20”. This works because in plan view the jack rafter runs the same distance along the plate line that it does running inboard towards the side of the hip rafter. In 3D it actually runs up hill though. So we take the plate line dimension and multiply it by the Line length ‘ratio’ to get the rafter length. With a common rafter we would just us the run to the ridge. That would be the span minus the ridge thickness divided in half times the Line length ratio to get the common rafter length.
What word is he saying before 20inches multiply the what?
“ The secant” or line length ratio. That is achieved by dividing the hypotenuse of the unit rises and unit run of the pitch (9/12) by 12 inches. So in this case, 15 inches divided by 12 equals 1-1/4. 1-1/4 x16” equals 20”. 20 is the common difference of the jacks.
you need 2 re explain better
Do you ever give out roof framing classes in the Chicago area?
If so when would be the next one?
I gave a roof class in Aurora. That class was instigating and organized by Carpenter who attended a class in California. Unless he organizes another one I probably won’t get there again.
@@roofcuttingandstacking7925 ok thanks for the reply and for your videos
Thankyou so much with the explanation in this video video I can cut all my jack rafter now I think
Winner of a video, I have been researching "pitching plate roof construction" for a while now, and I think this has helped. Ever heard of - Beybigail Nonpareil Breakthrough - (do a search on google ) ? It is a good one of a kind product for discovering how to create better sheds and improve your woodworking without the headache. Ive heard some pretty good things about it and my buddy got great results with it.
what i was taught to do. look at how the common and hip are nailed at the top think of the center of the common and the center of the hip take a common rafter lay it on edge with the bottom of the rafter facing up , so you would have the seat cut up. This rafter has been cut for the thickness of the ridge say you are cutting a 4 '' slope the distance between the jacks is 2' 1 1/4'' you are working at the bottom of the rafter let the tape stick over about7/8'' this will be where the end of the rafter would be if it had not been cut for the ridge . then measure down 2' 1 1/4'' that is the difference in length of the hip jacks on 24'' centers.. since you are working to the center of the hip you would shorten 1/2 the thickness of hip on a 45 degree angle or about 1'' 1/4 now measure back up 3/4 that is the long point of the side cut now from that mark put marks down the comm rafter 2' 1 /4 '' say you have 4 hips lay your pattern rafter on edge and put up at least 8 boards mark the seat cut on all 8 then go to the top mark the plum cuts at the mark on the comm rafter mark 4 away from you and 4 towards you then set your skill saw at 45 degrees and cut your mark then go down and with your pattern mark out the seat cut and over hang cut these on some jobs i would lay maybe 32 rafters and mark then with a long square
Interview question: Have an intelligent conversation with this guy and you get the job!
Do you have a question?
@@roofcuttingandstacking7925 No Sir. Came here looking for a video to teach the girls in the office how to better interview a guy who claims to be a framer. They need Framing 101. Yours is Graduate School level ;)
@@roofcuttingandstacking7925 i have a question you gave your email address before but I broke my old phone I was wondering if I could pick your brain on an upcoming project of valley roof framing thankyou for your videos and teaching you do a wonderful job of breaking things down so I understand, Bruce Rewa
@@brucerewa3232 nmridgeconstruction@yahoo.com
Hey on the shortening of the jack rafters , could you just deduct the common difference from the original measurement and that be to long point ?
yup
I missed this question. No because the offset would have to be 1-1/2” instead of 1” for that to work.
How to I get the angle for the rafters that join the hip
Its 45 degrees on a 90 degree corner. Its typically 1/2 the corner angle.
What do you mean multiply 16 by the factor?
Technically called the secant of the common rafter. The secant is obtained by using the square root method of the unit rises to determine the hypotenuse, then dividing it by 12. So if it was a 6/12 pitch it would be: 6 squared plus 12 squared equal, then push the square root button and divide the answer by 12 to put it in inches.
That would look like 36+ 144= 180, the square root of which is 13.416.
Divided by 12=1,118
@@roofcuttingandstacking7925 what's a secant? Also what about the 16 you were saying? Also wouldn't that be for a 12 inch run bigger the run bigger the number? So you devide your total rafter length by 12? Is that with or without the ridge dediluction?
I go over a whole bunch of that stuff on this channel. But essentially you take the secant and multiply it by the on center spacing to get the common difference of the Jack rafters.
@@roofcuttingandstacking7925 what's a secant
Its in the comments above.
How do I sign up for a class? Thx again for the info.
Ian Burnham Send me an email to nmridgeconstruction@yahoo and I will put you on the list. I take it you live in the San Francisco Bay area.?
Roof Cutting and Stacking will do I’m just south of Boston but would definitely travel to learn from you. Thx
I would fly to come learn from you too! Where do I sign up? I’ve learned more from mock up roofs in my garage then my framing boss ever taught me. I’d love to learn from you.
Wayne Send an email to and I am nmridgeconstruction@yahoo.com and I’ll put you on the list. They are eight hour classes, cost $200 and we build a big model , about 8’x14’
How did you get 20
9 squared plus 12 squared =225. The square root of 225 = 15”. That is 1 foot and a part of a foot. We want to make it one inch and a part of an inch. So divide it by 12. That equals 1.25. This is the secant of a 9/12 pitch roof. It is also known as the Line Length Ratio to us framers. Multiple it by the on center spacing of the rafters and it gives the common difference of the jack rafters. 1.25x16”on center equals 20”. This works because in plan view the jack rafter runs the same distance along the plate line that it does running inboard towards the side of the hip rafter. In 3D it actually runs up hill though. So we take the plate line dimension and multiply it by the Line length ‘ratio’ to get the rafter length.
With a common rafter we would just us the run to the ridge. That would be the span minus the ridge thickness divided in half times the Line length ratio to get the common rafter length.
Very helpful
Junius Rosario good!!!