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-   -   2/12 pitch trusses questions... (http://www.diychatroom.com/f9/2-12-pitch-trusses-questions-129312/)

BFT 01-08-2012 09:20 PM

2/12 pitch trusses questions...
 
I have the opportunity to buy 20' 2/12 trusses for a barn. This barn will house fairly expensive sheep(show quality) and we live just south of Branson Mo.

My questions...

I want to span the 20 feet with no center posts. I also want to go 5' OC with the trusses. We don't get alot of snow but I have seen 8" on our existing barn in the 10 years we been here. The roof will be metal and I have a surplus of 7/16 OSB that I could cut and nail to both sides of each truss for added strength. I have a tendancy to overbuild and make things much more stout than they need to be. Will a 2/12 pitch work for snow loads anywhere in Mo. at 5' OC? how about if I stiffen them with the OSB? Thanks in advance

joecaption 01-08-2012 09:28 PM

I would not trust spans that far apart.

titanoman 01-08-2012 09:59 PM

I live at the Lake of the Ozarks, not far from you. Branson is a beautiful place to live.
We get snow, then it melts, re-freezes. It's the weight of the ice that brings trees and power poles down, and many a boat dock.
I've seen trusses spanned 5 or 6 feet under skip sheeting under metal, but I don't know what kind of extra laterals or whatever are required.
Call a truss company or visit your local building department.
Be good to the sheep!

Sent from a Samsung Galaxy S2

BFT 01-08-2012 10:31 PM

most barn builders in the area use 4/12 at 5' oc. My existing barn trusses are on 4' centers. Like I said this is a good deal on trusses and by adding the plywood sides would still be way cheaper than buying 4/12 trusses from truss company. Truss company says no more than 4' OC with a 4/12 truss but they are in the business of selling additional trusses. They also say nothing less than 4/12 but again, less material, less money in truss builders pocket so I am skeptical of asking the truss manufacturer for his recommendations. I see barns here in the ozarks with minimal pitch and wonder how they have been around so long. I'm pretty confident the plywood sides would greatly increase the strength of the truss but I would certainly hate to be wrong since these show sheep are my kids animals.

Missouri Bound 01-08-2012 10:44 PM

How long is the barn? Can you just buy a few more trusses and close up the spacing? And where about's south of Branson? I live south of Branson as well.

titanoman 01-08-2012 10:55 PM

Quote:

Originally Posted by BFT
most barn builders in the area use 4/12 at 5' oc. My existing barn trusses are on 4' centers. Like I said this is a good deal on trusses and by adding the plywood sides would still be way cheaper than buying 4/12 trusses from truss company. Truss company says no more than 4' OC with a 4/12 truss but they are in the business of selling additional trusses. They also say nothing less than 4/12 but again, less material, less money in truss builders pocket so I am skeptical of asking the truss manufacturer for his recommendations. I see barns here in the ozarks with minimal pitch and wonder how they have been around so long. I'm pretty confident the plywood sides would greatly increase the strength of the truss but I would certainly hate to be wrong since these show sheep are my kids animals.

I'm thinking running rat-runs and lots of laterals would be far more beneficial than sheeting the trusses, if I'm underhanding you right.
You need them anyway to keep them straight everywhere.
And some 45's or whatever you can get on either gable end and throughout.
And unless they are from the South somewhere they were made in the first place, so they must pass code somewhere.
But the frequency, I don't know.
That's why I said to call a truss company.

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Gary in WA 01-08-2012 11:18 PM

All the trusses I've installed for 37 years have had engineering paper-work attached for the liability warranty........ So it collapses on the sheep and hopefully no humans, will your H.O. Insurance cover your losses because of missing paperwork? On-center spacing, etc....

Gary

titanoman 01-08-2012 11:30 PM

Never heard of such a thing. I'm just a 25+ year California Framer, and then new homes, big huge homes, for 10 years out here in Missouri.
But that's fine.
Edit: Never mind, I think. The more times I read your post, the more confused I get.
I think I will go to bed now.

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mae-ling 01-08-2012 11:35 PM

I know of one house, new house being built, that the trusses were under built. Owner sold it rather then replace roof. Guy talks to building inspector about putting plywood on one side of each rafter, gets an engineer's stamp on it, buys the house for cheap and finished it.

BFT 01-09-2012 12:21 AM

I am just outside Harrison Ar on Bull Shoals lake. The trusses are about 80 miles north of me. I just wondered if 2/12 trusses would work, we get one or two snows a year. Usually no more than 4" but have seen up to 8". We don't have inspections where I live other than leach lines. I moved here from Pheonix area where we were overwhelmed with inspections. My opinion on inspections is probably right in the middle of Phoenix and where I live now. Too much sucks, not enough sucks. I wouldn't even question if this were possible if it were for a home, but since its for a barn and the question is wether the 1-3 snow falls we MIGHT get a year would if we get could be withstood by some 2/12 trusses with some glued and screwed plywood to the sides of the trusses. Its no big deal, I can wait on some other trusses to show up. I just wondered how much plywood sides would stiffen up the trusses, kinda like I-joists. I guess they are cheap enough to buy and plywood the sides and drive my tractor over the trusses and see if they hold the weight of that or how much flex there is. If they hold, I could use them, if not then I sell the remaining trusses to someone else that will come here looking for advice on 2/12 trusses.

Since these are listed on craigslist and are used, there is likely no spec sheet with them. And I wouldn't need them here.

Daniel Holzman 01-09-2012 08:07 AM

There are three ways I can think of to know the load capacity of a truss. The best method is to get a calculation sheet from the manufacturer. Since these are Craigs list trusses, that may not be possible.

Method two is to compute the load capacity. This is almost certainly not a DIY exercise, unless you happen to be a structural engineer. Load capacity is a function of the geometry of the truss, the size of the members, and the strength of the joints, all factors that would be taken into account by a professional engineer you hired to evaluate the strength of your trusses.

Method three is to guess, which is all you can possibly get from an internet chat forum, unless someone on here is willing to perform truss analysis over the internet free on a truss they have never seen. Now that would be unprofessional, and if I were to be so stupid as to do that, I could lose my engineering license, so neither I, not any other professional engineer on this forum, would consider it. However, there may be someone on here willing to offer an opinion as to the strength of the truss. So, are you feeling lucky today?

My recommendation is to check out the trusses in person, take some photos, and attempt to determine who built them. If they were home built, you absolutely will need professional analysis to know the load capacity of the trusses.

titanoman 01-09-2012 09:58 AM

Quote:

Originally Posted by BFT
I am just outside Harrison Ar on Bull Shoals lake. The trusses are about 80 miles north of me. I just wondered if 2/12 trusses would work, we get one or two snows a year. Usually no more than 4" but have seen up to 8". We don't have inspections where I live other than leach lines. I moved here from Pheonix area where we were overwhelmed with inspections. My opinion on inspections is probably right in the middle of Phoenix and where I live now. Too much sucks, not enough sucks. I wouldn't even question if this were possible if it were for a home, but since its for a barn and the question is wether the 1-3 snow falls we MIGHT get a year would if we get could be withstood by some 2/12 trusses with some glued and screwed plywood to the sides of the trusses. Its no big deal, I can wait on some other trusses to show up. I just wondered how much plywood sides would stiffen up the trusses, kinda like I-joists. I guess they are cheap enough to buy and plywood the sides and drive my tractor over the trusses and see if they hold the weight of that or how much flex there is. If they hold, I could use them, if not then I sell the remaining trusses to someone else that will come here looking for advice on 2/12 trusses.

Since these are listed on craigslist and are used, there is likely no spec sheet with them. And I wouldn't need them here.

I don't think any truss manufacturer calls for a giant gusset covering the whole truss.
You guys do weird things in Phoenix.
But you are in the Ozarks now, might as well start building like an Ozarkian.

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mae-ling 01-09-2012 12:40 PM

Quote:

Originally Posted by titanoman (Post 817355)
I don't think any truss manufacturer calls for a giant gusset covering the whole truss.

Sent from a Samsung Galaxy S2

We have seen this spec'd for girder trusses.

titanoman 01-09-2012 02:21 PM

Quote:

Originally Posted by mae-ling

We have seen this spec'd for girder trusses.

Girder trusses, yes.
You don't usually have to get strongbacks or laterals through girders.

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abracaboom 01-10-2012 04:05 AM

If those trusses are the typical ones made out of 2x4s, I wouldn't space them over 2 feet apart.

The only way I would space trusses 5 feet apart is they they were much more solid than 2x4s and had purlins or 2x6 sheathing on top. Especially if I'm going to be doing the roofing!


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