Can a hip roof be built over two different widths? We have built a house and have a ledger on three sides. We want a 10′ porch roof on the east and west side and a 15′ porch roof on the south side. Naturally, we also want the beam upon which the tails rest to be level all around, changing the pitch from 3 in 12 to nearly 2 in 12. Is that possible? It seems like it should be but our builder insists that the pitch must be identical all around. Thanks for your help.
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Replies
Someone, like Joe Carola or Dieselpig may chime in here and give you the specifics.
When I'm faced with something like this, I rely on my experience as a boatbuilder and am reassured that most anything is possible.
Changing pitches and widths terminating in a common line is most often possible...just takes a builder who knows how.
2/12's pretty shallow - where are you / what kind of roofing?
Forrest
We have a standing seam type metal roof. It is rated to 3 in 12. My architect tells me that in order to so the shallower roof, we need to put a layer of asphalt roofing under the metal. Fine with me.
We have a standing seam type metal roof. It is rated to 3 in 12. My architect tells me that in order to so the shallower roof, we need to put a layer of asphalt roofing under the metal. Fine with me.
As I always ask architects when they want to do something contrary to the materials limitations or contrary to what my experience tells me: "Are you willing to warrant that?"
You must stay within the proprietary installation instructions.
All this raises another question. If you've got an architect, how come he can't answer this framing question? Not trying to pick at you. This just sounds peculiar and I often get to see the heartbreak caused by a faulty roof installation.
http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
my architect doesn't have a problem with it. My builder does. He says that hip roofs always cover the same distance on one side of a corner (say, going out 10') as around the corner. I'll admit that it seems to work out that way most of the time. I just want to know if can be done.
my architect doesn't have a problem with it. My builder does. He says that hip roofs always cover the same distance on one side of a corner (say, going out 10') as around the corner. I'll admit that it seems to work out that way most of the time. I just want to know if can be done.
Your builder is right, traditionally. But it can and is often done. It even has a name: bastard hip. Good luck.http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
"bastard hip." also known as an irregular hip in polite circles (not here). Bob's next test date: 12/10/07
Sure it is.
If the roof calculations start from a given height at the beam what will vary is the length of the tails ( to arrive at the same eave height).
In your example the tails on the shallow pitch will be 1/2 again longer the the steep pitch tails.
Hap ( Height above plate) must be the same for both roof slopes.
Edit to correct myself .
;-)
They can't get your Goat if you don't tell them where it is hidden.
Edited 5/28/2008 12:16 am by dovetail97128
yes, the ledger, the lower beam and the eaves (rafter tails?) need to all be at the same height - consistent height, not the same as each other, obviously. The only thing that differs is the horizontal distance, which, I understand, changes the pitch which is where is the rub. Can it be done? Is it done? It seems to me that one should just be able to place the joist (?) in the corner (from the corner of the house to the corner of the edge of the porch) and then 'just' hang the parallel joists from there. I have made roofs before but never a hip roof (I don't plan to make this one) and I seem to always forget what different boards are called. Sorry.
Half again longer? So, if we want an overhang of 2', we need to have, say, 2' 3" tails along the 10' wide side and 4' 6" tails along the 15' wide side? Maybe I am not understanding. Please forgive my inexperience.
Lets make it simple. You have one triangle that has a pitch of 3/12 pitch and a base of 10'.
The rise for that triangle is going to be 2'6" (3" x 10= 30") Now you have a triangle with a pitch of 2/12 and a run of 15'.
The rise for that triangle is going to be 2'6" (2" x 15= 30") For every 12" of eave over hang you have with the 3/12 pitch rafters you drop 3" in vertical elevation.
To match that 3" drop with the 2/12 roof you have to extend the rafters out 18". (2" x 1.5= 3") It is the ratio of the amount of rise over 12" of run that counts.
With these pitches it is an easy math problem as the 3" is 50% greater than the 2". The run of the hip is the hypotenuse of a triangle that is 10' on one side and 15' on the other. (A sq. + B sq. =C sq.) or 18' 0" 21/64.
Rise of hip is 2'6", Run of hip 18' 0" 21/64 we just found.
Hip would be 18'2" 25/64ths. Make sense?
They can't get your Goat if you don't tell them where it is hidden.
Sorry , By length I meant length of the Run of the rafter , not the actual rafter length. 2' (24") overhang along the 10' wide side? OK here is how it works out. 2' = run , pitch is 3/12 so rise (or in the case of tails, the amount the rafter elevation drops over a 2' horizontal measurement) = 6" 6" @ 2/12 pitch = 3'(36") = Run of low slope rafters 24" (Run of high slope rafters) x 1.5 = 36" ( Run of low slope rafters) They can't get your Goat if you don't tell them where it is hidden.Edited for clarity. 5/28/2008 9:49 am by dovetail97128
Edited 5/28/2008 10:41 am by dovetail97128
Good answer and good explanation!
Still a good explanation. I would like to see a drawing of this.
I went back and corrected my post to reflect his "overhang" dimension. That should help make it clear. Drawing would be nice, not something I am able to do though.
They can't get your Goat if you don't tell them where it is hidden.
Not yours, his.
Ah. Got it.
They can't get your Goat if you don't tell them where it is hidden.
knew you would. I love pictures!
yes
Bob's next test date: 12/10/07
Short answer is that anything is possible.
Now, a "pure" hip roof on a rectangular plan is slightly less fun to frame, from having two different pitches with not-quite-on-the-square cuts for all those jack rafters . .
Now, you can get your builder's request for only having one pitch--you'll just need a very short ridgebeam parallel to the longer dimension of the plan rectangle. In an ideal world, that ridge would be an even number of 16" spacing--the world, sadly, is seldom ideal.
Ha ha....my answer was shorter. Bob's next test date: 12/10/07
my answer was shorter
Strooth.Occupational hazard of my occupation not being around (sorry Bubba)
Is that ledger set at the same height because of windows above and you can't raise the ledger on the 15' run south side to make it 3/12 to match the east and west side?
If there re windows involved, you can always make the 15' run 3/12 to match pitches all the way around to window wells in.
If you can't do that and the ledgers have to sty the same height, you'll have a bastard hip at each end.
What is the overhang and what is the width of the south wall?
Also, how do you know that your pitches are 3/12 and 2/12 with a fixe3d ledger height.
You can't figure the rise by measuring from the top of the girders to the top of the ledger and determine that because you haven't taken the HAP cut in consideration and the size of the rafters.
Also, you should always figure the rafters for bastard hip including the overhang. In other words, work from the back of the fascia.
What size rafters re you using?
I knew you would be along.
OK, lots of good questions. I am looking at the architect's drawings (which I can't read very well because they are copied on regular size paper and so are printed pretty small): The rise (from the top of the ledger to the bottom of the beam running parallel to the house) seems to be really close to 4'. The run on the east and west sides are 10' and on the south side is 15'. I guess I worked it out when I first drew it to be roughly 3 in 12 on the east and west sides and 2 in 12 on the south, probably from counting on my graph paper (amateur, sorry!). And yes, I see that the rafter tails are longer on the south side; 2' 7 1/8" on the east and west and 4' 0 11/16" on the south. No, the ledger cannot be changed. It is already built into the siding of the house and, yes, there are windows. Even if we could raise it on the south side, wouldn't it be tough to wrap a roof around a corner if the ledger is suddenly, say, 8" taller on one side? What do you do in between, build a vertical wall? I picture it as being awkward. I think it would be great if I could see some pictures of buildings with hip roofs that are longer on one side than the other. If anyone knows of any on the internet, please let me know the website. Or, if you have some to post, let me know where to see them. Thanks so much.
I just want to say that Framer is correct about the need to figure the roof from the end of the overhangs back to the building. I have been lacking sleep lately and was getting brain dead while trying to post to you. What you want built can be done though , no question about that .
They can't get your Goat if you don't tell them where it is hidden.
This is an example of how I frame this roof with the same pitch and two different runs.
Joe Carola
Thanks for the picture. Pictures are sure handy. Unfortunately, the ledger is already set and can't be changed. However, I did look up a bastard hip on the internet and that was very helpful.
Little off topic but......
Bastard hips aren't common, but they are out there. If the builder you have is not even aware of the concept of bastard hips, maybe this is not a good project for him to do. Or maybe it would be a great project, he would be able to learn/ figure something new.
How comfortable are you with this builder?Live by the sword, die by the sword....choose your sword wisely.
Very, actually. He built our SIP house (a first for him) and he is an artist. However, he is a bit 'ol school when it comes to building. That is why I want to be able to assure him that this can be done and, indeed, has been done. Pictures would be great.
Best way to convince someone is to show them drawings they can read. Can you draw you own project to scale? It isn't very difficult and if your anything at all like me it really puts the pieces together in my mind . They can't get your Goat if you don't tell them where it is hidden.
Edited 5/31/2008 3:03 am by dovetail97128
"Best way to convince someone is to show them drawings they can read.Can you draw you own project to scale? "Better yet, can his archy draw it?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
http://images.google.com/images?um=1&hl=en&safe=off&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=%22bastard+hip%22+%2B+roof&btnG=Search+ImagesMaybe you will need to buy a book for your framer
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
True, I asked that because the OP seemed interested in actually learning something about it himself. Sheet of ply and about 3"= 1' scale would work nicely. But you are correct , the archy should be able to detail the plans for this.
They can't get your Goat if you don't tell them where it is hidden.
This is one of those situations where for HO DIY, I would probably draw it all out and post here, if they could give the right detailed info, but SOMEBODY - the framer or the archy - is getting paid to do this, so i am not gonna step on their toes or do their work for them for free.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
We never worked on residential prints that would draw and specify any of that. We had the elevations, which showed intent. That means they'd show the projections and the drawings would show level fascias. The interior would spec the ceiling heights.
We'd calculate and figure everything out given those parameters. In most (not all) situations, the truss companies would use those same criteria and of course create the truss package, with the appropriate HAPs and projections. In most cases, there isn't a need for detailed drawings. For the most part, it's simple math, once it's settled in the mind for what it is...simple math. Of course, I had the benefit of going through trade school and we actually had a semester on unequal pitched roofs (all the cuts were with a handsaw LOL). So, the basis for the calculations were already hidden in my brain somewhere when I was first faced with the bastard hip package. My main problem that day was that I was staring at my first hip package! In those days, nobody ever sent any paperwork with the package LOL! Bob's next test date: 12/10/07
I just got prosperoed on a long texst to you, LOLIn your case, you would be the guy getting paid to figure out the details. You are right they don't normally need to be drawn out.Bu this Op has a builder who is a blockhead and needs to be taught. So the archy needs to draw it out in detail for him.BTW, I have had plans from architects that I knew could not be built. When it became clear that the archy considered me too stupid to know how to build them, I backed off from arguing and simply acted dumb and put in the request for working drawings to show me how.That is the point where the archy discovered that I was right, he was wrong, and the plans got changed before coming back to me. It allowed him to save face, but privately I got in a wink and a dig.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Yes, I've had those conversations with builders and architects too. One in particular was funny. Neither the builder or the architect could figure out how to get a set of stairs installed/drawn and accomplish their goals. After an hour of discussion we finally told them to just let us build it. The architect came back after we were done so he could draw it to submit it to the city for approval LOL! The architect was an uncle to one of my guys and even though he knew him, he still looked down his nose at us! Bob's next test date: 12/10/07
Yeah, I've had those "retro-drawn" details too.On one of my best staircases, the owner did not really like the way it was drawn in. I said why not do it this way?HO says the archy told him it could not be done that way. I had a mockup done in an hour and he said built it.week or ten day later, the archy sent his drafts person out to draw it up and put his name on the drawing.Things like that is one reason I started designing things myself
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
BTW, there was an interesting thread on this in another forum a year ago.http://www.contractortalk.com/showthread.php?t=23454
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks for the link, I envy Joe's gift with numbers. I have always struggled with that part of it so to compensate I at first bought the good framing squares with tables, then books that someone else had done the numbers work for, and finally the construction calculators when they came out. I can draw these things out to scale and make it work, but using someone else's printed knowledge is much easier and faster. Very first home I contracted was an octagon that was about 30' wide and 50' long. Had to learn what uneven pitches were in a damn hurry and I still to this day have never forgotten the hip run for an octagon, the need to figure in the differing overhang lengths (well except when I am posting here too late at night after a week of little sleep!), and constant haps. I had to have a math whiz of a buddy figure that roof out and we still struggled with it.
They can't get your Goat if you don't tell them where it is hidden.
Thats good that your comfortable with him. Started wondering last night, is it that your g.c. says that bastard roofs cant be build or that it cant be done the way the arch. has it drawn ( with overhangs and fascia all aligning nice and perfect)?
There are a number of framing books out there dealing with bastard roofs, few books out there just on roof framing. Might be worth it to get a few for your g.c. If I get motivated, Ill try and look at what I have/ like........but Im one of the last here to give roof framing advice.
Good luck.
Live by the sword, die by the sword....choose your sword wisely.
Am I wrong thinking that the fascia and soffit can be aligned? Won't the porch beam just need to be built up for one of the sides? I'm almost certain I've done it this way before.
Rich
Not wrong at all. You might google “Irregular pitches with equal overhangs” to find more about it. There is a current discussion over at the JLC framing forum as well.
No, You are correct . That is one method of doing it.
They can't get your Goat if you don't tell them where it is hidden.
Bastard hips are very common in many areas. I struggled through my first one back in 1988 for a builder and after that, they started appearing on most roofs. After 1988, probably 90% of the roofs I did were bastard hips. The architects started using that technique to make the roof appear larger and steep. They sloped most side roofs at 40 degrees or above and sloped the front to back roofs somewhere in the 30 degree range. This also created a wider ridge on most houses instead of creating such a pointy roofline. I was working in the N Metro Detroit suburbs during those years. Bob's next test date: 12/10/07
We havwe also seen an increase in basterd hips while framing in Syracuse,NY during the last 15 years. It used to be very uncommon, but now it has almost become 50-50.
I was working in custom neighborhoods that ushered in the "McMansion" era back in the late 80's. The average home had suddenly grew from a 2500 sf open first floor plan to 3500 sf McMansion. They were quite common everywhere in the more affluent suburbs and the steep roofs suddenly appeared in every sub.
Bob's next test date: 12/10/07
tell me about it, gotta love them steep roofs. I call them young roofers retirement money. Guy in his 20's today in roofing will be reroofing those stupid roofs in time to make a lot of money for their retirement!
Lots of fun getting the rafters to work, when you start, now I just wish them rafters were lighter!
Guy in his 20's today in roofing will be reroofing those stupid roofs in time to make a lot of money for their retirement!
Trying to understand your thinking here: How's a steep, complicated roof gonna wear out any faster than than a lower pitched, simple roof? My experience seems to dictate the opposite. What am I missing?http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
they are not, because they are steeper and take longer more money can be made when it comes time to replace.
A person in their 20's will be in their 50's when these roofs need replacing, their is their retirement money!<G>
OK, I see.http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
That's a lot higher percentage than see around here ( maybe, Ill have to pay more attention is see how common it is around here).Live by the sword, die by the sword....choose your sword wisely.
Take a digital picture of the plans and post them please. Bob's next test date: 12/10/07
yes it is possible, but it is not easy.
It is doable.
Your framer just needs to step up to the plate and learn a couple new skills.
to have the supporting beam at the same elevation and the same size with differing pitches, you will have the overhang longer or the fascia higher on one pitch than the other.
one way to compensate might be to have a diff beam size
This is your architect's job to detail if the builder cannot figure it out.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!