Gable/Hip Roof Conversion from Hip roof

Hello,
I'm new to this group but I thought I would post a question about something I'd like to do. Some history first: I currently have a detached 3-car garage (about 30'x22') and it has a hip roof on it and ~8' ceilings. I am looking at buying an automotive lift and need additional ceiling height over the double bay. The hip roof has another 3' above the ceiling joists at the peak so with the pitch of the hip roof, there still isn't enough room even with the ceiling joists removed to get the 14 or so feet hight I'm looking for. I would like to have a gable constructed (I'm assuming trussed) that spans from front to back over the double bay. I would most likely leave the rest of the roofing structure alone and would want the new gable roof to be tied in somehow. Looking at the roof rafters they are 2x6s and where the hips come to a point (don't know what that's called) there is a brace going down to a ceiling joist (which by the way are 2x12s 24"OC) for support. The brace on the far side is over the 1 bay area that will not be modified in any way. The other brace is over the area I need opened up and would be getting replaced by the gable. There are also 2 2x6s going across to form an "A" every 4th rafter. My question is, structurally will the addition of a gable present any problems? The one side of the gable would go to an exterior wall, the other side of the gable would need to be attached somewhere not sure if the 2x12 could hold this as the gable would end up perpendicular to the 2x12, or if it would need to be attached somewhere else.
Any ideas on the approach or if there's a better way to do this would be greatly appreciated. Also is this a huge job or can it be reasonably done (i.e. would I be looking at a $3K job or a $10K job?) I'm trying to make this determination because if it turns out to be too expensive it may be a better option to just do an addition to the garage.
Thanks in advance for your help and suggestions.
Nick.
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snipped-for-privacy@onwebcenter.com wrote:

pictures here would definitely help. but in any case, there is no way to really say from a description, especially when you don't really have your terminology correct. for example, by "braces" do you mean "hip rafters"? and you are wanting to cut half of a hip roof away? this sounds like a complicated bit of framing. at any rate, i would say the first place to start is with a good contractor. you will have to have this engineered (which the contractor can do via a truss company) as well get a permit etc. (which the contractor will also have experience with). as to price, that's impossible to really say from here. but way more than 3k. closer to 10k, if not more.
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Hello Marson and thank you for your reply. I will try to take some pictures and provide a link. I tried to answer some of the questions below the best I could:

The hip rafters are 2x6s and they come together at the ridge. The edges of that ridge have a vertical brace (it's actually 2 2x4s nailed together to form a T) that goes from the edge of the ridge to a 2x12 ceiling joist.

gable/truss to the double-bay so I can vault the ceiling to get additional height. If there's another way to do it with less work, that would be fantastic, I just don't know of any.

have as many ideas as possible prior to them coming out.
Thank you so much for your advice - I'll take some photos and post the link here.
Nick.
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Best I can tell you have an approximate 3 on 12 pitch, has collar ties on some of the rafters, and the approximate 8' ridge rides on a 2X12 beam below at attic level.
You want to make part of the roof gable type. Beginning at one wall, but not ending on the other. Rather, somewhere before that. And, it appears, that the clearance you need of 14', is not there even with all the joists removed. It appears to me, that the roof itself is also too low by your description. Especially where they tie to the top plate at 8' high. Puttng another roof on it is a moot point, if all of this is correct.
--
Jonny



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Hello Jonny,
Thank you for your response. Here's some additional info that may help still working on the pictures.

I've got another 4 feet to the ridge from the bottom of the ceiling joists - your description on the colar ties sounds correct though. On the pitch I'm not sure, but the angle looks to be about 35-45 degrees.

The long side of the hip is oriented long-wise from left to right on the garage. I would like to add a gable over the 2-bay going from the front wall all the way to the back wall with a steeper pitch to get the height needed - right now, adding everything up as is with the hip I have a total height of 12' from floor to ridge, but with the pitch on the hip it nets a lower total height as you go towards the front and rear wall. So a portion of the hip definitely needs to go. I was assuming that a gable going from the front wall all the way to the back wall could dramatically increase my overall height and as the pitch would change from front to back to left to right, the maximum roof (and ceiling height) would end up square in the middle of the 2-bay where I need it.
I hope the above clarifies it a little more....
Thanks again, Nick.
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