Laying Out an Irregular Valley Rafter

Keith,

I appreciate you taking the time to reply. If I may clear something's up. I step-off many a roof, that's not where I'm have the trouble. I having the trouble with the way you described how to step-off the irregular hip rafter.

You said;¿That number should be 24 1/16". This number is your run per 12" of rise on your irregular hip or valley. Now take a common rafter that intersect the same ridge and multiply its pitch buy half the building width to get the ridge hieght. Example: 8" pitch * 10'= 80". Then simply step down 80" from the top of the ridge with your square reading 12" on 24 1/16". "

It is the last line in the above statement that I'm not getting.

To layout a common rafter on that roof you'd make ten steps of ~14-7/16", so how many would you make on the irregular hip and how long would they be?

Joe, what I mean is that instead of stepping OUT in 12" increments of RUN like you would for the common rafter you would step DOWN in 12" increments of rise for your irregular hip or Valley.

Keith

Joe, what I mean is that instead of stepping OUT in 12" increments of RUN like you would for the common rafter you would step DOWN in 12" increments of RISE for your irregular hip or Valley.

Keith

When you say step out 14 7/16, that is rafter length per 12" of run on an 8" pitch. If you wanted to do it that way for the irregular hip or valley the number would be 26 7/8" of rafter length per 12" of rise using a 12" on 24 1/16" pitch.

Sorry, I didn't catch that in the last post.

Keith

So the total irregular rafter length would be 14' 11 1/4". Double check that with your framing calculator out of curiosity. the pitchs are 8 on 12 and 9 on 12 and the smaller building width would be 20' on the 8 pitch side. I hope its right or I'm going to look like a real a*%hole.

Keith,

Thanks for hanging in there, but I just don't get it and most likely never will. I just don't know what 12" increments of RISE means.

If I use my unit length of 17-15/16" for an 8/12 9/12 hip roof with an 8" rise and a 20' span that I post previously and step it off 10 times on the hip rafter I would get a total length of 14'-3/8". So your numbers are close enough for government work.

My point is that whatever the number of steps are for the common rafter should be the same for the irregular hip rafter, in this case 10.

Keith,

It should have read 14' 11-3/8"

Check your math again because if you multiply 17 15/16" times 10 you get 14' 11.375". Not 14 3/8. I don't know where you got that number from. Thats pretty close to 14' 11 1/4" if you ask me.

Keith

And no I don't work for the government.

Throw me a freeking bone here it's only an 1/8 of an inch and I used completely different numbers than you did. I used 26.888 divided by 12 multiplied by 80. That's 179.2533332= 14' 11 1/4" heavy. so that's not even a saw blades thickness.

Keith

Regardless of the equation both of our ways work and thats all that matters. What's an 1/8" bettween framers anyway. I hope that you understand how I got my numbers, because it is important to know the principal behind an irregular hip or valley and how the square works in ways you can't emagine. By the way I would love to see the article in JLC on irregular hips and valleys. Where could I find it and what issue is it in.

Keith

Joe
You had remarked in one your posts about cutting irregular pitch roofs with a framing square.
Fred Hodgson's "Practical Uses of the Steel Square" printed in 1903, has the information you seek. Hodgson was trying to convince carpenters to use the square since the 1870's
Also you find how to layout that same roof
without a square.

Keith,

It wasn't my math that was bad it was my typing ;-}.

Rocky,

Thanks for the tip on the book. Ill see if I can get my hands on a copy.

Let me see if I have this straight.

Joe:

I think the part you're missing is that for his stepping DOWN, Keith is not looking for a number of steps, but 80 inches worth of 12 inch steps. Or 6 full steps and an 8 inch step DOWN, holding on the appropriate run.

Is that right, Keith?

C(ain't no real framer but likes learning)X

Haven't checked out the site for awhile, and it looks like I missed a good post. I have to say, that although I do use a calculator, I would rather use my square, and my approach is very similar to Keith's, although I do not do it everyday. I would just like to add that the square can do anything that you can think of. It will not only lay out irregular valleys, but it will also find the length. A hip roof with two corners seriously out of square can be figured, and all the cuts that need to be made. It will give you any length for any rafter, no matter how long, with no multiplication or division needed. It's right there on the square. It will lay out any ellipse, any circle, any oval. It will construct a bicycle track. It will constuct a five sided star. It will layout shingles and siding. The steel square will solve any problem for circular, octagonal, hexagonal, and square roofs. The 12's edge of the square will get you anything.

I could go on, but what I wanted to say was to get some of those old books that one of the posters suggested, such as Hodgson. He put out many of them, as he was extremely renowned for his knowledge of the square. His later additions circa 1940 or so would be of more value as he revised his earlier editions for easier learning. Also, Stoddard put out some excellent books on the square. I have both, and many different editions. You won't find it anywhere else. Wouldn't be fair for me to toot my horn on this, as I have had these books for many years.

Once you start thinking in a different format, you will be able to solve just about anything that you wouldn't think possible. To give you an idea, one problem that popped up was putting an ellipse over a door that was 7 ft. wide. They wanted the top of the ellipse 2 ft. high. What was the center of the door to be set at? What is the center of the ellipse? Simple if you know how to use the square. No math involved. The secret is moving the square with the right numbers. Get the books, and you will have fun learning.