different roof pitches on a multi level
I’m sure some of you fellows have run into the problem of different roof pitches on multi level hip roofs. I have an architect who wants to run the ridge with the short span of the house which of course calls for different pitches. The long span has a 12/12 and the short span has a 8/12. I can make that work with different plate heights. But have you ever got to a point on a roof where you knew that it could not be built the way it was drawn? I think I have gotten there. He drew a 12/12 garage roof plugging into an 8/12 hip with the hips and valleys running at long angles(not 45) and keeping the overhang the same and the hips and valleys running parallel to each other. Am I missing something? Is there a good source on impossible framing situations?
JAMES
Replies
James,
"I have an architect who wants to run the ridge with the short span of the house which of course calls for different pitches. The long span has a 12/12 and the short span has a 8/12."
James, are the plans something like my drawing?
If they are, it will not work the way they're are drawn because the steeper pitch has to go with the shorter run.
This kind of stuff happens all the time and it's good that you caught it now because now you can tell them that it wont work.
It can be framed that way but in order for the short span rise to meet the 12/12 long span rise, it would be 2-3 times the 12/12 pitch depending on the dimensions of the house and if he gives you the ridge length that runs parallel to the short span wall or the short span run.
What is the dimension of the house?
Joe Carola
Thanks Joe for your reply.
The roof is exactly like you drew it. The only dimensions that I can arrive at is that it is 32' X 40'. This is by scaling with a rule. WE have already framed the high hip which is like the one you drew. This particular part of the roof sits on a 5' knee wall and is separate from the rest of the roof. I wish I could draw the other part but I do not know how to do that on the computer. The other roof sit on the wall plate and is 44' X I'm not sure how long because it runs into the higher roof. He also ran the ridge with the short span. The truth is, I have made this roof work but it is not right. We used strings and made the hips and valleys plane out but they do not run parallel. I went over this with the builder first to see if he wanted to get the architect. The roof looks good but I know that something should have been done different.
JAMES
Joe, I do need to add one thing to your drawing. The 12/12 is where you have the 8/12 and the 8/12 runs up to the ridge.
It's hard to say what's up without seeing the drawings, but if Framers picture is right with the pitches switched, it seems right to me. Lets say the long span was 24', the run being 12', than the 8/12 would put the ridge at 96". The 12/12 woul only run 8' to reach 96", thus your hips will not be 45degrees as the ridge will continue out untill it disects the 12/12 common making this a "bastard" hip. To make these meet at the facia lin you need to adjust your heel on your seat cuts. For every foot of overhang the 12 is going to drop 4" mor than the 8 so your 12?12 needs to be taller where it passe over the plate linne, which also pushes your hip off the exact corner due to the height difference. Well, after all that hot air I probably answered the wrong qestion and you already knew all this!
Since you're alread into the framing, this is kinda sticky.
I run into this all the time. The architects/CAD jockeys who draw the prints don't generally like to hear that they've screwed up. So you're kinda in a bind.
Attached you should see a pic of one of the worst houses I've ever dealt with. It had 12/12 and 10/12 hips that planed out from 5 different wall heights on the first floor and up over the 2nd floor. (I did the trusses for it) The plan was from "Design Basics", which cranks out horrible plans, IMHO. There were several errors in the plans and the company was no help at all in fixing them.
It might help at this point to sketch up some section views to try to illustrate to the HO and architect what's going to happen in certain areas. Or do a plan view of the ridge lines to show what's wrong and where.
The house in the picture ended up having shortened walls in several places on the 2nd floor, with the ceilings sloped until they reached the full 2nd floor height. The HO and GC were pretty understanding but it was still a nightmare.
A lady is one who only shows her underwear intentionally.
The house we are on looks like the house in your picture. The GC understands but the architect is not helping at all. The GC is demanding a full refund on the plans. Like I said, we are almost done but I know that things should have been done differently than we did them. I do not understand the intersection of different roof pitches like I want to. I do know how to make intersecting valleys and hips plain out and that helped on this roof. But I would like to understand the geometry of what was going on(or what could not go on). I've ordered a couple of books on advanced roof framing and I hope they help.
JAMES
I think I learned how to figure out what was happening by doing just exactly what I suggested - Drawing plan views of the ridge lines and section views. It's hard to visualize things in 3 dimensions.
Of course - You could always start using roof trusses. Then let the truss company explain to the architect why the roof won't work.................(-:A miser is hard to live with, but makes a fine ancestor.
James,
I know where your coming from and you bring up very valid points. Fortunately there's some good books out there that could help in these situations. The good part about you is that you know the situation is not right from just looking at the plans and you built it right. So it might not have went as fast as you like but you did right.
Now is the time to find out ways to do it the right way as you have but just a little faster and not breaking your back as much.
I'll give you a link where every single thing your talking about and asking about is there.
Hope this helps.
Joe Carola
http://www.jlconline.com/cgi-bin/jlconline.storefront/3e4664860044535c271a401e1d2905dd/Catalog/1139
Nice work Boss
um,
your house only has four gable-ends visible from the front of the house. The trend in our area is at least five irrelevant gables.
remodeler
ps and it had something of a side yard. totally unacceptable.
These people could only afford to spend half a mil, so they simplified it some................(-:Which is harder -- to make education entertaining or entertainment educational?