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Old 12-04-2006, 08:07 AM   #1
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Gambrel Attic Roof Truss


I want to build a barn with an an apartment in the attic.

I want the barn to be 40 x 60 with no poles supporting the ceiling/floor for the apartment.

First off, is this possible, or would I need to go to a smaller span?

If this is possible, where do I get the dimensional information for the truss required?

I have a little program called Easy Rafters http://www.easyrafters.com/, that calculates the truss based on span. However I need information on what size lumber would be required to span 40' with no load beaing poles, and also the center spacing of the trusses.

I'll contact a lumber yard I know that builds trusses, but was looking to see if I could find this information on the net...

Was hoping someone here could help me!

Thanks!

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Old 12-04-2006, 12:34 PM   #2
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Your trusses/joists would need to be engineered for a 40 foot span,
especially with a live load on the 2nd floor.

Steel web joists would be required for a 40 foot span, the size to be
determined by an architect or engineer.

I have used engineered wood joists spanning up to 26 feet.
If you could somehow split the span to 20 feet, these would
work for you and save the cost of engineering. Your truss
company should have items like this pre-engineered.

Splitting the span without posts would be expensive.
A 60 foot glu-lam would cost a fortune in fabrication,transportation,
and installation.

Good Luck

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Old 12-04-2006, 12:43 PM   #3
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Well, I just talked to a local truss manufacturer, explained what I wanted and they are going to send me a few options...

From the way the guy sounded on the phone, 40' span was not a big deal...

Only thing he said was a they have to be 12' or less in height to ship...

That means a pretty squatty Gambrel Roof for a 40' span...

He said they also offer a split truss & I-joist system, where I build the floor with sheeting first, then put up the slpit trusses. It's more work, but I actually like that idea better...

He's going to give me prices too...
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Old 12-04-2006, 01:51 PM   #4
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Gambrel Attic Roof Truss


I built a 36'x36' building with a 17'x36' upstairs in it. These were trusses and if I remember correctly was an 8/12 pitch. The bottom chord was 2x10, the top chords 2x6. They came flat on a truck, weighed about 400 lbs each.
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Old 12-10-2006, 10:58 PM   #5
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I have been a truss designer for the past 16 years on and off. A 40 foot Gambrel truss should pose absolutely no problems. As for the 12 foot delivery width restriction, there are a couple of different options. The trusses can be designed with a hinged top portion which is folded up after the trusses are erected. I personally dont like this option because there are too many chances for the hinge joint to be damaged in handling, unloading and durring erection. The better option would be to cap the truss. This involves designing a truss to a shipping width of 12 feet and having a second truss which sits on top of the first. Ive used this method literally hundreds of times. Talk to your truss manufacturer about this option. Hope this helps. I just wonder why they didn't suggest this solution...
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Old 12-11-2006, 05:14 AM   #6
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Well, I talked to the truss designer. He looked at using a split truss. Where the truss would come in two halves. He told me that design would not work, as the 40' span was too great for a split truss.

I came up with a solution, whereby I use a regular 5/12 pitch shed truss on top of second story walls wich are 30' apart, then frame in the lower section of the gambrel with stick & frame constructuon. The upper stud wall will sit on floor trusses that can handle the 40' span. This will also enable me to stick frame in the dormers without hacking apart any of the trusses...

You can see my design in the following picture. The purchased trusses are shown in red. I'm looking at ~$12,000 in trusses...

http://usera.imagecave.com/bhaal/Car...uss_Config.JPG
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Old 12-11-2006, 11:31 AM   #7
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I hope that price includes the floor trusses, seems high to me.
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Old 12-11-2006, 11:52 AM   #8
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Yes, the floor trusses are the expensive ones...

I need 31 of them, and they are ~$280 each...

2x8 for the cords, 2x4 for the webs...

24" tall floor trusses...

The roof trusses are $90 each, and all 2x4 construction...
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Old 12-11-2006, 01:36 PM   #9
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Gotcha, good luck.
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Old 12-26-2006, 09:39 PM   #10
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Gambrel Attic Roof Truss


Quote:
Originally Posted by ETD66SS View Post
Well, I just talked to a local truss manufacturer, explained what I wanted and they are going to send me a few options...

From the way the guy sounded on the phone, 40' span was not a big deal...

Only thing he said was a they have to be 12' or less in height to ship...

That means a pretty squatty Gambrel Roof for a 40' span...

He said they also offer a split truss & I-joist system, where I build the floor with sheeting first, then put up the slpit trusses. It's more work, but I actually like that idea better...

He's going to give me prices too...
I too am looking for information on Gambrel trusses. I have a 30 x 50 floor plan. I' m attempting to put a second floor on and I liked the idea of a split truss system that was pictured. I am trying to maximize space usage.
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Old 01-31-2007, 10:07 PM   #11
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Gambrel Attic Roof Truss


Hey,

Capping a 40' truss is not a problem, done all the time.

The hinge as stated is problematic and most contractors don't like 'em

Caution: If you do decide to go with an I-Joist or Floor Truss system make sure the point loads generated from the knee wall from the roof down to the floor system is accounted for!



Gazelle, <'/))))><
www.wwtbi.com
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Old 02-06-2007, 03:20 PM   #12
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Gambrel Attic Roof Truss


Thanks for the website. It had some pretty good information. My hope for a Gambrel style roof slipping a bit. I am try to maximize storage space on a second level so I am thinking of doing full two story with 4/12 roof top. I my change the pitch if i cannot keep the peak below 25 feet. As you can see I am somewhat flexible on the second story.

Thanks
KG
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Old 02-24-2007, 11:58 PM   #13
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Gambrel Attic Roof Truss


If you still have not sorted out the problem then check out, www.barnplans.com ,they will provide you with the plans for the complete building including engineered trusses.All you then have to do is decide the size of the building and where you want to put the walls for the rooms inside

Last edited by Wolfman51; 02-24-2007 at 11:59 PM. Reason: spelling mistakes
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Old 02-25-2007, 01:16 PM   #14
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Thanks for your response. The website is a great reference. Still in planning phases so I have not completely decided on the final plan yet. Stiil looking at 30' X 50'.
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Old 03-06-2007, 07:55 PM   #15
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Gambrel Attic Roof Truss


your plan looks like a good compromise if it passes engineering with your local loading. Make sure you specify ceiling load, dead load and live load for living space not attic storage to all be factored in along with truss, roof and snow load for those "bottom cord trusses." A design as this will be very specific with fasteners, brackets and bracing. Make sure to follow that.

Bonus... your picture looks almost identical to a garage I built last year. Im on the laptop right now but I'll post a picture tomorrow.

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