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Old 08-14-2012, 11:51 AM   #1
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Roof Framing help - Cathedral Garage Roof with Trolley


Hey everyone!

So, I'm a little ways off from building the new shop/garage (more than a year until pouring the slab), so I'm using this time to really plan and learn, and figure out what is best for what I need work space and storage wise, but also architectually pleasing, and makes sense from a construction standpoint. Time is definitely on my side, and money is NOT! HAHA!

So, I've been drawing up a few different concepts. One thing that has become very apparent to me is, I do the best work in a shop with high ceilings and room to spread out. So, I've been toying with the idea of a deep 3-bay shop that's mostly open over two bays and a loft for storage over the other. I ALSO want to hoist from an I-beam and be able to lift to the loft space. Sick of tripping over stuff, so anything that's not being used will go in the loft and out of the work area.

So what I've been thinking is, a cathedral ceiling would work the best for hoisting as well as giving that nice open feel. Maybe a bit more work than your standard truss roof, but I know it's something I can be happy with and would be functional for everything I need to do as well. The roof pitch will more than likely be 12-12 or POSSIBLY 14-12 to match the house. The house has a 14-12 pitch. I will probably just go 12-12 to make life easier, though.

The real interesting part of the concept is, the I-beam for the hoist trolley. The I-beam and trolley will be rated for 2000 to 2500 pounds and I need it as high up as possible so I can hoist into the loft area. I'm thinking if I can span the I-beam between two posts/columns AND tie it into the ridge beam then I can support not only the hoisted load, but also share some of the roof load. Obviously the math will need to be done to see what beam sizes I can get away with for static and live loads, but one thing at a time. The concept.

Here's the concept I like the best, so far. Sorry these are a little blurry. Had to use my cell phone. They were even WORSE as scans.







So here's the questions... (please disregard the added rooms on the back for the sake of discussion, for the time being)

1) Does the concept of the I-beam tied into the ridge beam and supported at either end of the span (over two bays and approximately 24-feet) make sense?

2) Would I get the most bang for the buck with 2x10 rafters? 2x12?

3) How about the ridge beam itself? 2x12's with additional 2x?'s above that for nailers? Or maybe a composite beam?? What makes sense from a construction and financial point of view?

4) Would I need to replan all this to use collar ties at the ridge?

5) Am I providing enough information?

6) Am I out of my mind?

Again, I'll stress, this is all just conceptual at this point. I'll probably change this floor plan again and again, but I feel good that the cathedral ceiling/roof over the 2-bays is the way to go for my needs. So, maybe we can focus on the rafter and roof construction more than anything. I need to CAD everything up to get a better sense of the floorplan before finalizing anything anyway.

Have a look at the sketches. Hopefully it's clear enough to get the point accross.

Thanks for any input!

Cheers!
Scott


Last edited by scootermcrad; 08-14-2012 at 11:55 AM.
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Old 08-14-2012, 12:58 PM   #2
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Roof Framing help - Cathedral Garage Roof with Trolley


Just in case the Trolley thing isn't clear, this is the style hoist trolley I'm planning on using....


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Old 08-14-2012, 01:10 PM   #3
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Roof Framing help - Cathedral Garage Roof with Trolley


I would recommend checking with your building department in regards to the use of an exposed steel beam that is used to support structural loads.

In my area structural steel beams used in a garage are required to provide fire protection for the beam as steel is a thermoplastic and will expand when heated pushing out at either end or bending in the center and failing.

You may be able to have a structural ridge designed and have your I-beam a separate non-structural component used in your lift.

Like the idea though ......
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Old 08-14-2012, 02:42 PM   #4
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Roof Framing help - Cathedral Garage Roof with Trolley


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Originally Posted by GBrackins View Post
I would recommend checking with your building department in regards to the use of an exposed steel beam that is used to support structural loads.

In my area structural steel beams used in a garage are required to provide fire protection for the beam as steel is a thermoplastic and will expand when heated pushing out at either end or bending in the center and failing.

You may be able to have a structural ridge designed and have your I-beam a separate non-structural component used in your lift.

Like the idea though ......
Hmmm... Very interesting. I'll check into that. Thanks!

Yeah, I was thinking the I-beam could be treated sepately, if needed. Support the I-beam by columns and use traditional construction methods for the cathedral roof with rafters and a ridge beam/board, treating them as two separate structures independent of eachother. I would think tying the columns into the wall structure for lateral support would be worth while, though. Maybe not...

Keep the info coming guys! THANKS!
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Old 08-15-2012, 06:30 AM   #5
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Roof Framing help - Cathedral Garage Roof with Trolley


New day... any other thoughts, framing folks??
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Old 08-15-2012, 07:23 AM   #6
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Roof Framing help - Cathedral Garage Roof with Trolley


I like your setup, that would be nice. One thing I am concerned about is using the ridge beam to support the steel girder. It actually should be the other way around. No extra load should be placed on the ridge beam. It is very questionable using 2X12s on a 20 span to start with. I personally wouldn't try that, although you could use 3/4 inch plywood and more than two 2X12s and bolted together but then your inspector may have something to say about that.

If it were mine I would go with a steel ridge beam or an engineered wooden beam designed to handle that kind of span. I would not allow the steel girder for the trolly to place any stress on the ridge beam at all, I would use the posts that support the trolly girder to help support the trolly girder and the ridge beam. JMHO
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Old 08-15-2012, 08:23 AM   #7
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Roof Framing help - Cathedral Garage Roof with Trolley


Quote:
Originally Posted by jiju1943 View Post
I like your setup, that would be nice. One thing I am concerned about is using the ridge beam to support the steel girder. It actually should be the other way around. No extra load should be placed on the ridge beam. It is very questionable using 2X12s on a 20 span to start with. I personally wouldn't try that, although you could use 3/4 inch plywood and more than two 2X12s and bolted together but then your inspector may have something to say about that.

If it were mine I would go with a steel ridge beam or an engineered wooden beam designed to handle that kind of span. I would not allow the steel girder for the trolly to place any stress on the ridge beam at all, I would use the posts that support the trolly girder to help support the trolly girder and the ridge beam. JMHO
Yeah, I'm beginning to think this is also the correct solution. Isolate the I-beam from the Ridge Beam and treat it as a seperate load model and on it's own support posts/columns.

So, let's treat it like that for a minute. Two seperate structures.

Any thoughts on the supporting columns for the I-beam being tied to the wall structure for lateral support while also being bolted to the floor?

Leaving the I beam out of the equation for the roof itself, what would be the ideal rafter size and ridge beam design? With a 12-12 pitch on the roof, that will make the effected loading covering about a 17-foot roof face, give or take. And the cathedral portion would span over a 24 foot section (give or take). Bang for the buck vs. structure, does an engineered ridge beam just make the most sense in this case? Should this ridge beam also be supported by it's own posts/columns? The ridge beam would probably span the full width of the garage (36 feet +), but could be supported at 24 feet where the cathedral portion ends.

Great input! Keep it coming! Thanks!

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