I have been framing custom homes for seven years, but I have never found anyone who can show me how to accurately cut an ovoerhang on a hip rafter before it is set into place. I can walk a framing square, use a calculator, and understand complex geomotry yet no-one can give me a straight answer.
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Replies
I think Blue, or Joe or some of the other framers are about to give you a crash course in Trig and use of a Construction Master Pro.
BTW, it would be nice if you filled in some of the details of your profile. Where you work, etc.
Keep your head down.
Quality repairs for your home.
AaronR Construction
Vancouver, Canada
Edited 3/9/2005 9:41 pm ET by Aaron Rosenthal
college never pointed me in the right direction. I learned a lot of use-less info. My real professors were french-canadian framers from the old school who learned from their fathers and their fathers. I guess they never knew...
ran ito the same problem a few years back my self. we had those built in gutters too. 2 crews and a wiz with a construction calc had no clue. we put them up and ended up stringlining it. wasted a few bucks in timber as well.
good luck i hope someone has a true answer for this oneTmaxxx
Urban Workshop Ltd
Vancouver B.C.
Chef,
There's a lot of ways to tell you, to start with hips that run 45° multiply the overhang of the common rafter x the square root of 2 which is 1.414214 and that will give you the run of the hip overhang for example 12" overhang.
12 x 1.414214 = 16.97" or 17".
If you notice the 17", when you have a common pitch of 5/12 you will hold your square for the hip/val 5/17 to mark the plunb cuts because for every 12" of run on the common the rise would be 5" and the hip running at 45° for every 5" of rise the run would be 17".
Mark your plumbcut at the outside corner building line with the framing square at 5/17 and then mark the 17" mark and that's your overhang length.
If you have a 16" overhang.
16 x 1.414214 = 22.62742" or 22-5/8"
Do the same thing by marking your 5/17 plumbcut mark at the outside corner building line and side the square down on the plumbcut mark until you can mark the 22-5/8" mark and that will be your overhang.
If you us tables on the framing square for a 5/12 pitch the Hip/Valley Rafter Length line says 17.69" or 17-11/16" that would be the hip overhang length if you measured from the plumbcut at the top of the rafter on your birdsmouth outside corner line and down marking the top of the hip and that would be the hip length.
If the overhang was 16".
16/12 = 1.333333 x 17.69 = 23.58667" or 23-9/16" (Hip Overhang Length)
If you had a Construction Master Calculator using 5/12 pitch 12" overhang.
5 [Inch] [Pitch]
12 [Inch] [Run]
Press [Hip/Val] Returns 17-11/16" (Hip Overhang Length)
Using a 16" overhang.
5 [Inch] [Pitch]
16 [Inch] [Run]
Press [Hip/Val] Returns = 23-9/16" (Hip Overhang Length)
The easiest way for any equal overhang which is a perfect square to find the diagonal which is the hip run is to multiply the length x 1.414214.
Or you can just mark the corner of a sheet of plywood 12" one way and 12" the other way and you will get 17".
It's like a walk out bay that has a 2' projection the diagonal measurment to be close enough would be 34" or 24 x 1.414214 = 33-15/16".
Amen. That is what is says in the Carpenters 4th edition, the textbook for carp apprentices up here in Canada, eh.
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Here's a couple drawings. I hope these can help.
Man thats cool!! thanks for taking the time!______________________________________________
--> measure once / scribble several lines / spend some time figuring out wich scribble / cut the wrong line / get mad
Your drawing pretty much covers how I did it for years. Grab a straight edge and a sheet of plywood and lay it all out. Works just about everytime.
I'm amazed at how many guys will use painfully complex equations to solve simply problems when they could do it twice as fast the caveman way.
Chef, I'm assuming that "walking" the framing square is the same as "stepping" off the framing square.
I'm puzzled about what confuses you regarding the overhang. I'm puzzled because if you can step off the rafter, why can't you step off the projection?
What method are you currently using to determine your total length of the hip? Are you calculating, stepping it off, or using a book?
blue
Just because you can, doesn't mean you should!
Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!
Huck,
Great drawing!! Got any more?