I’m trying to design a 4:12 hip roof with unequal overhangs due to some jogs in walls. How is this done to keep the ceiling elevation the same in the house? I’ve seen interior soffits used to hide the roof rafters on the bumped out portion. Is this the only solution? I have 1-foot bump outs along several walls with new and existing construction.
Also, in drawing a plan view of 4:12 hips, are the angles 45-degrees?
Thanks in advance.
Replies
Any way to post a drawing and dimensions of the roof in plan view?
You can have a 4/12 hip roof with jogs in and out all over the place with equal overhangs everywhere with the hips running at 45°.
Thanks for the quick response. I've included a pdf for discussion purposes. Actually, I have a couple of questions:
1. At the wall jogs, the height of my wall top plate will be different, or I need a soffit, or ?
2. At the peak that I have clouded - how do I design the valley that is intersecting the ridge?
Thanks again for your help. I am trying to prepare drawings for permitting, and these issues have me stumped.
I'm with Joe. Wall dimensions needed. Meanwhile, here is a rough sketch. The roof is see-thru blue, and the ceiling is opaque, so you can see where the wall height is above ceiling height.View Image
View Image bakersfieldremodel.com
Edited 8/23/2009 4:39 am by Huck
Huck - that is a pretty impressive and clear graphic. If it is not a bother, can you sketch up what I just recently sent at the peak so I can see what is going on there?
Thanks,
Kaorisdad
Shrunk the drawinmg a little.Joe Carola
Joe - How do you turn off the 3D effect, to get a flat 2D drawing like that with Sketchup?View Image bakersfieldremodel.com
Huck,
Not sure I understand what you're saying. Try this.
1) View
2) Face Style
3) Click "Shaded"
Joe Carola
I'd like to help you out, but your drawing (which is all I have to work with) is goofy - or else your existing house is. The existing ridge, as you've drawn it, is not centered on the house. What's up with that?View Image bakersfieldremodel.com
Design roof flat on bottom at house footprint. Make bearing walls taller as needed to meet roof bottom. Some walls have to rake.
In your PDF, SE corner has shortest wall, SW has tallest. Make all ceilings same as SE.
View ImageSamTA Pragmatic Classical Liberal, aka Libertarian.
I'm always right! Except when I'm not.
That drawing would be plenty enough for me to frame your house. In fact, most of the houses I did, were done without a plan view of the roof. I started getting them from the truss companies in the 90's however. Framers don't really need a plan view of the roof to frame it. It basically plays itself out.
Your clouded area does not need any more detail. That situation will occur and the framer will just do it.
You have a couple choices on dealing with the issues you've raised:
1)you either have to raise the height of the walls and maintain a uniform heel
or
2)maintain the uniform height of the walls and raise the height of the heel.
I'd opt for #2. I'd build all the exterior walls at 9' and then the heel on the walls with the 2' overhang would be 4" greater than the heels in the areas with 12" overhangs.
So, depending on how critical your insulation needs are: I'd put a 6" heel on the roof components and then bump it up to 10" where needed.
This is great - thanks all for your responses. I can see that I need to be more precise in my dimensions. I'll revise my sketch and post again later. I sketched something approximate for discussion, but I'll redo it with actual dimensions.
I obviously came to the right place. It's great to have this resource available. All of your expertise is really appreciated.
It seems that varying the wall heights is fine... but what about the continuous chords I need for my seismic? The top plates act as tension/compression ties for lateral loads and are supposed to be continuous - I live in earthquake country. With the different height walls, how do I keep the top plates continuous? Or are 'cripples' installed on top of the higher walls?
Again, thanks all for the detailed responses.
Kaorisdad
Depends on the variance. It might be as simple as adding blocking beween joists that the rafters sit on - or that, in conjunction with varying the seat-cut (height-above-plate). 4:12 is a pretty shallow pitch, depending on the offset of the walls, you're not talking about a whole lot of difference. At any rate, rafter ties, usually every 4', can tie the rafters together across the span of the roof.View Image bakersfieldremodel.com
Good point Huck.
He might also decide to slightly adjust the distance of the overhangs to simplify the blocking proposition. For instance, he's currently proposing a 12" difference which will produce a 4" height adjustment. Maybe he might want to increase or decreas that so two blocks or three blocks would work perfectly.
For two blocks (3" difference) he'd have to have only a 9" diffence in overhangs.
For three blocks (4.5" diff), he'd have to increase the overhang difference to 13.5".
There are lots of ways to skin a cat...or design overhangs and roof systems.
I don't have any experience in seismic country. So, if I were building in a seismic country, I would intstinctively choose to let the truss companies design trusses for me and expect them to survive any earthquake.
I would let them tell me what the best solution is regarding heel heights and plate heights.
But, with that said, I would also think that maintaining the same height plates would be far easier and stronger with regard to the issues youve raised.
It appears to me that your drawing has some fundamental problems. So you've started with a faulty drawing, and you're asking for help to finish it correctly. But you can't finish correctly what was begun incorrectly.
You have some good minds here willing to work with you. I think your best option would be to show us what you have (existing) walls and roof wise, and what you want to add, walls wise. Then let us show you some roof options to tie into what you have.
View Image bakersfieldremodel.com
Edited 8/23/2009 7:40 pm by Huck
I'll try and get some measurements of the existing. I have some drawings that were done by an engineer previously for a remodel that I was using as a base, but I know there are some errors from spot checking measurements. The only measurement I am unsure of is where the existing ridge is - everything else shown is new. I believe Joe has shown what I would like to do in the new area. Will this work? If the new ridge doesn't line up with the existing, couldn't I add a break in the ridge? My house already has one (that will be demolished as part of this remodel).
I'm kind of unsure how much detail I need to add for a framer. My previous remodel was done with less info than I am showing here. The framers just made it work somehow. Joe's comment previously seems to be the norm. Of course all the hips, ridge members, rafters, etc. will be properly sized.
Thanks again for your help.
I'm kind of unsure how much detail I need to add for a framer. My previous remodel was done with less info than I am showing here.
A good framer will figure it out. A good drawing will ensure that what gets built is done the way you would want it done.
Your drawing shows an existing house with a 5' overhang on the south side, and a 3' overhang on the north side, but with equal pitch on either side. Is this what you have? Are the walls at the same height, or differing? If the walls are at the same height, then the fascia is at a different height on the north than on the south. Is that the case? If the fascia is at the same height, then the walls are different heights. If both fascia and walls are at the same height, then the roof pitch is different on each side. Which one is it?
If the new ridge doesn't line up with the existing, couldn't I add a break in the ridge?
Sure, but that would look really funky, and lead to some odd detailing.
View Image bakersfieldremodel.com
Edited 8/23/2009 8:08 pm by Huck
Is this the way it's supposed to look with the offset ridge, 4/12 all the way around and same fascia heights all the way around?
Joe Carola
Joe,
Yes, that is it - I haven't measured the existing ridge yet, but that is very close. The facia is the same elevation all the way around the entire house. What you show as a porch with a post is actually just an extended eave on the front of the house. I've attached a pic of the "South" elevation. The existing East side of the house will be demolished and rebuilt as I've shown which starts at about the second window from the right side of the picture. The East side was a garage that was converted to livable space at some point in the past. However, the slab is at grade and water migrates into the interior causing mold. As part of the remedy (building a proper foundation and flor slab above grade), I decided to add some space, building forward (South) and back (North). You can see the angled driveway I mentioned a few emails ago.
Kaorisdad
kinda hard to tell from your photo, but if it has a boxed eave (soffit), it'll probably look something like thisView ImageView Image bakersfieldremodel.com
What's the measurement of the front where the 5' overhang is. I noticed that's a hip roof also. Is the front 3'?Joe Carola
Hopefully the o.p. will give some clarification. This is what I think is happening:View ImageView Image bakersfieldremodel.com
Can you put the dimensions on every wall?
Your wall heights can vary according to the roof, while the ceiling heights remain constant. Ceilings do not have to sit on the top plate.
After looking at the plan. . . The question that begs to be asked is why not frame the roof where all the overhangs are equal? Just add a hip or two and move the valley a bit and you are there.
View Image
http://www.josephfusco.org
http://www.constructionforumsonline.com
Edited 8/23/2009 2:50 pm ET by Joe
Why would that particular question "beg to be asked"?
The idea of straight clean line at the eave might appeal to some people (me).
Jim,Considering what's needed to achieve that look it might just be easier all the way around to frame it the way the plan dictates it. Like I said for me the first question would be, why can't the overhangs be equal.http://www.josephfusco.orghttp://www.constructionforumsonline.com
Edited 8/23/2009 11:14 pm ET by Joe
Like I said for me the first question would be, why can't the overhangs be equal.
Joe,
They can be equal with keeping a 4/12 pitch all the way. The only thing is that the right side width is smaller than the front porch side and lower side that have the same span. Where the 1' jog is can be a hip and valley. That creates a small level spot at the top of the roof which isn't that bad.
Joe Carola
I would rather not have that flat spot on top. If I extended the eave to 4-feet and 3-feet on the East side (the eave would be straight running N/S like shown in Post 21), would this get rid of that flat spot?
I would rather not have that flat spot on top.
If the existing house is 30' across, fascia to fascia, as you've drawn it, and the addition is 30' fascia to fascia, as you've drawn it (24' house, 3' overhang west side, 3' overhang east side), then there should be no flat spot - the ridges will meet at the same height.
--------------------------------------------
edited to add: Oh, I see, the flat spot occurs because Joe added a little valley where the roof jogs. I personally don't see any purpose for that, but different strokes for different folks. I'd build it just as I drew it.
View Image bakersfieldremodel.com
Edited 8/24/2009 3:03 pm by Huck
Heck, why not move the walls too?;)Adding extra valleys might create water dumps in bad spots below
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Why isn't the valley sitting on the corner? The jogs can be framed with hips and valleys and all overhangs can be the same. Is there some reason why that overhnag looks like it's around 4' where the valley is? You need to post the dimensions.
Edited 8/23/2009 2:56 pm ET by Framer
Yeah, there is an existing 4-5-ft overhang that is existing. I'll sketch something with actual dimensions and post later today.
Would this be alright with the overhang at 4' top right side?
Notice that you left side where the existing roof and 5' overhang is where the valley sits is the same 30' fascia to fascia as the right side 30'. Therefore your ridges are the same height and same span. The top right hand corner gives you the same span and the hip offsets the corner creating a 4' overhang just in that spot. Plates would have to be raised a little for the back 2' overhang to work.Joe Carola
Framer,
Yes, that would be fine. I had it that way originally, but wasn't sure if the hip had to line up with the corner? Your diagram is the way I'll go, with the exception being the below comment to Huck.
Huck,
Is the ridge normally centered on the walls or the roof? I had it shown centered on the roof, but if it is easier, center it on the walls. Thinking about it, I suppose it should be centered on the walls.
Is the ridge normally centered on the walls or the roof? I had it shown centered on the roof, but if it is easier, center it on the walls. Thinking about it, I suppose it should be centered on the walls.
On an existing house, it is what it is. You want your addition to tie into what is there. You have to draw what is there, accurately, in order to design a roof that will tie in. As you have drawn it, the ridge is not centered on anything.
Sometimes this is done, with uneven pitches, in order to keep the fascia at the same height. But you show a ridge not centered on anything, with equal pitches on both sides, and a fascia that will be 8" higher on the north side of your addition than it is on the south side. So your exterior walls are differing heights, and your fascia is on differing heights. That seems unlikely, but if its the case, you need to spell out exactly what is going on with the existing roof.
View Image bakersfieldremodel.com
Edited 8/23/2009 7:47 pm by Huck
Got it - this makes sense. I'll measure the existing roof tomorrow and take a pic of the existing.
Thanks again.
Got it - this makes sense. I'll measure the existing roof tomorrow and take a pic of the existing.
OK, great! I feel like we're on track to get you a solid answer you can build with.View Image bakersfieldremodel.com
In the first drawing, the roof pitch is the same on both sides, and the ridge is centered between the fascia on each side.
In the second drawing, the roof pitch is the same on both sides, and the ridge is centered between the walls.
In the third drawing, the roof pitch is different on each side, and the ridge just ends up where the two pitches meet, not centered on anything.
You should have (existing) one of the three.
View ImageView Image bakersfieldremodel.com
Huck,
I'm thinking it's gotta be the third - the pitch must be different as you show. I'll try and verify tomorrow.
Thanks
looking at your picture, I'm thinking its fascia the same height, walls different height. If so, here's the new roofView ImageView Image bakersfieldremodel.com
View ImageView Image bakersfieldremodel.com
View ImageView Image bakersfieldremodel.com
View ImageView Image bakersfieldremodel.com
If you keep the new room addition the same span or less than the existing main span, and the minimum overhang equal (2’) then the plate heights can stay equal to the existing with a couple of 4” raised plates ( Adjusted heel heights?) at the 3’ overhangs (2’ + 1’ offset). Huck’s first illustration is the closet to what I'm describing and would personally like for its clean simplicity. The pitches remains equal too. (As Joe C. shows in post 21)
Edited 8/24/2009 12:39 am ET by MrJalapeno
I'm thinking it's gotta be the third - the pitch must be different as you show.
Why does the pitch have to be different?
Can you change the porch overhang to 4' and then make the left side the same 4' and the rest will be 3' like everywhere else? This way the front has the ridge in the center with the left side overhang matching the porch overhang.
Joe Carola
Edited 8/24/2009 2:42 am ET by Framer
Why does the pitch have to be different?
I agree. Looking at his photo, I doubt the pitch is different. They wouldn't have done that on a tract home. I think the fascia is at the same height all the way around, and the ridge is centered between the south side fascia and the north side fascia, differing overhangs notwithstanding.
I don't think he can readily change the overhangs, as he is tying into the existing structure, and that's whats already there - 5' overhang in front (south), and 3' overhang in back (north). The right side in the photo is coming off, to make room for the new addition. The angled driveway causes the building and the roof to be clipped in that back corner, for vehicles.View ImageView Image bakersfieldremodel.com
Here is my sketchup model, if anyone wants to tinker with it
View Image bakersfieldremodel.com
Huck,
You are probably right about the pitch.
You are correct about the overhangs and tying into the existing structure. You are also correct about the right side of the structure and the driveway and clipping the back corner for vehicle clearance. Your graphic depicts what I intend on doing. It would appear that I would have to have different height walls to accomplish this.
It would appear that I would have to have different height walls to accomplish this.
There are other ways. You can frame your walls at the same height, then brace each rafter down to the top plate, its not that big a deal to do. Same concept as a purlin with kickers transfering the load down to a bearing wall, except I doubt you'd have room for a purlin! I would just make sure the framer is clear on the design, then let him frame it as he sees fit. Unless you're framing it yourself, in which case you need to decide ahead of time.
Then again, different height walls is no big deal, either. Pretty simple affair on this little addition.View Image bakersfieldremodel.com
Huck/Joe,
Thanks to you and the rest for your considerable time and effort on my addition. I will show it as you have described and go over ahead of time with the framer what I would like done. Really, as long as the fascia is kept level all around the house, and the tie into the existing ridge is relatively clean, that is all I care about. I also need the 3-foot overhang on the South side for appearance to match the 3-feet overhangs elsewhere.
As an aside from this, where I am building requires a Conditional Use Permit for my eaves which are mostly 3-feet. The Planning Department has a goofy ordinance that limits percentages of lot coverage. If the eaves were 2-feet, the lot coverage is just the livable area (to the walls). For eaves greater than 2-feet, I have to count the area of the roof eaves which put me over the lot coverage maximum.
Sorry to put you guys through so much effort. I just wasn't sure of how much detail I really needed to provide to the framer. I think I have a pretty good idea now.
Kaorisda
something like this (I drew the purlin in)View ImageView Image bakersfieldremodel.com
Hmmm, I would have to be able to get my roof diaphragm seismic loads transferred to the walls and chords. Bit of a challenge, but doable. I just have to make sure I provide details to address the different wall conditions. I might have to do this after I talk with a framer.
I would have to be able to get my roof diaphragm seismic loads transferred to the walls and chords.
That's exactly what I drew. Not sure where the challenge is, you must know something I don't! Where do you live - top of Mt. St. Helens? Hahahaha. =)View Image bakersfieldremodel.com
Lol. No, this is in the Pasadena/San Gabriel Valley area in SoCal.
The seismic loads in your graphic are running parallel to the wall and purlin. Usually, this is accomplished by nailing the plywood to blocking, and then clipping the blocking to the top plate of the wall with Simpson clips. The top plate drags the seismic load to a shearwall. With the diaphragm elevated as you have shown, I don't see any continuity between the diaphragm (plywood) and the wall.
I am an engineer, but I really don't do any residential work. Thus, the perhaps silly questions about this roof and details.
I'd be surprised if the city required it, on such a small addition, but if they did, or it you just wanted it for peace of mind, there are any number of ways that could be pretty easily accomplished. I just wanted to illustrate how to frame the walls at uniform height, then transfer the roof load to them.
BTW, my mom lives in NoHo/Burbank area, and I need to get down and visit her. Do you need a general contractor on this? Then I could drop by my other favorite spot - Gamble House!View Image
View Image bakersfieldremodel.com
Edited 8/24/2009 4:45 pm by Huck
Thanks for the offer, but I think I have a contractor in mind. I do have your link and when I get close to bidding I'll keep your company in mind. I'm quite a ways off from that point though. I have to go through a Design Review Committee, Planning Commission approval for a Conditional Use Permit, and then the Building Permit process.
If you use 2x8 ceiling joists and 2x8 rafters for example, your front cross section with the rafters on the left side with the 3' overhang sitting on the top plate will allow you on the right side with the 5' overhang to nail a plate across the top of the joists and put a birdsmouth on the rafter. Extend the ceiling joist all the way out to the end of the rafter at the overhang. This will tie everything in.
Joe Carola
The existing eaves just have 2x4s extending out. The house was originally built in the 40's. I plan to splice a 2x4 extension onto the new 2x8 rafters to keep the look the same.
What size the existing ceiling joists?
Joe Carola
I think they are 2x6, but I'm not sure. I know the new will be 2x6 @ 16-inches.
I know the new will be 2x6 @ 16-inches.
You'll just have to add 2 plates using 2x6 joists.
View ImageJoe Carola
Actually, maybe they are 2x6's extending out. I need to check that.
Another shot with the roof.Joe Carola
Joe - would you just go over there and build the doggone thing, and get it over with? Take less time than we're spending here! =)View Image bakersfieldremodel.com
That looks like it's covering the front porch with the porch being 4 or 5' wide.
Is their some reason why you feel that the valley must lay over the corner?
Yes, there is an existing 5-foot overhanging eave. Attached is my detailed sketch showing existing and new for discussion.
I'm still confused where the new valley hits the ridge peak. I can't visualize how that will fit. Is this something that framers just figure out?
Basically, the job scope is a new addition as shown. Most of the existing eaves are 3-feet, except in the front, where it varies from 3-feet to 5-feet (I didn't show that). I'm restricted on space on the North, South and West sides. The West side 'jog' is because of a angled driveway that runs N/S. I need this jog to maintain adequate sideyard clearances.
Similarly, the jog on the North side is because I'm trying to maximize interior space, and it is as far back as I can go. Every foot makes a difference in this particular addition.
Thanks again for everyone's input.