Hello from Montana! Pole Barn w/ attic question?

[suavilica]

Hi there,

I am new to GJ!

I would like to build a pole barn with a attic bonus room. My builder thinks it is possible with triple glued attic trusses on 8' OC. Building will be 40' Long, 30' Wide, 14' Walls with 8/12 pitch roof. South side of the roof will have 36 solar panels. Bonus room will be used for my computer business. It will be insulated and heated. Builder will erect the building and I will do the rest of the work on building the office room in the attic.

My first question is how would I build the floor in this room. Run 8' 2x4 between trusses with joist hangers?

Second question any idea what would be the weight limit with triple trusses on each pole on every 8'.

Any suggestions apricated!

Thanks!

 

[22george]

welcome

 

[930dreamer]

Welcome to the GJ,I'll move your post to the General Garage discussion if you want= more topic related.

 

[suavilica]

Will do. Thanks!

 

[gearhead1]

Re: Pole Barn Attic Trusses...

I’d recommend talking to a truss designer or civil (structural) engineer. I ordered standard attic trusses (24” O.C.) and the loading is clearly stated on the drawing.

 

[Ecreps]

Re: Pole Barn Attic Trusses...

I think you would find this easier, and possibly cheaper to do if you just used standard 2x6 stick building on 24" centers.

 

[383]

Re: Pole Barn Attic Trusses...

The truss manufacturer will design the trusses for the specs that you request. If it takes a two, three, or four ply truss for any particular situation is up to their engineering. They will also design it for the floor loading required. Here it is 50 lbs/sqft for residential, if you are using it for business it would be considered commercial and require at least 75 lbs/sqft.

A 2x4 is never enough for a floor system, you will probably need to match whatever the truss manufacturer uses for the bottom chord of the truss.

 

[MikeF2316]

Welcome.

I'm not a structural engineer but I do know this: 8 feet is too long a span for 2x4s unless you want a springy floor. And trusses are designed for loads at certain points, make sure yours are designed to support a floor where and how you want it.

 

[fourbyford]

I agree with the above comment... 2 x 4's would not be adequate... may be borderline dangerous. 2 x 6's would be the minimum... 16" o/c would give you an acceptable floor... depending on the loading.
As far as capacity of the trusses...
The folks that build your trusses will have to answer that. I'm sure your builder will be very specific when ordering them. When he specifies attic trusses... tripled on 8' centers, they will design the bottom chord to do the job. The more info you can provide on loading will be helpful in achieving the best design.
Good luck with your project!
...D

 

[fourbyford]

Just had another thought... do you plan to extend the floor the full width of the building?? Some builds do that to use the space under the roof pitch for storage. If that's your plan, the truss designer should know that as well... along with how much weight may eventually land there.
...D

 

[matt_i]

Re: Pole Barn Attic Trusses...

I worked (as a helper) with my neighbor who did similar build with ganging up the attic trusses into packs of 4 and then bridging across with joist hangers and 2x8s (??) Same dimension as the bottom chord of the floor for insulation reasons. He had previously worked this all out with the truss company.

However, you see the potential for concentrating a lot of load on the posts. His build was a stick framed with a full concrete foundation to bear the loads. And, as the building goes higher, his was 12' interior, there is a lot of potential for side loading, where the ply/osb sheathing is adding up shear resistance. Its not there in a post frame and you'd be well served to think about some metal X-bracing all over, wherever it could be installed.

One other thing worth noting, in an already tall first floor and having an attic 2nd floor, the trusses were extremely tall and long. We had access to a telehandler/shooting boom rough terrain forklift but the geometry had it maxed out and barely able to set the trusses down before the boom would touch the top of the wall. A game of inches holding ~1500# seemingly a mile out there. It was successful though and is being finished on the interior.

 

[theoldwizard1]

i would like to build a pole barn with a attic bonus room. My builder thinks ...
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.
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Second question any idea what would be the weight limit with triple trusses on each pole on every 8'.

You need engineered drawings !

 

[NUTTSGT]

Welcome, I see 930 moved your original thread but you started a second one.

I've merged both thread and deleted the second double post.

 

[speed bump]

Assuming your pole building manufacturer knows how this is going to be built your upstairs should be good for 40 lb PSF. I'm under motivated to do the calculations to tell you roughly what size the post needs to be but i'm going to guess somewhere in 5-7 laminated 2x6 range.

A quick look at the span tables says a doug fir 2x6 (typically this is what you will get if you buy number #1 construction lumber in MT) spaced 24 OC will do 8' 8" on a 40 PSF floor load.

All things considered, if you don't know how to spec out the floor joists have your builder take care of it. Unless you have a pile of equipment and love hand nailing joist hangers and handling 4x8" sheets of sub flooring they will do in a day what takes you 2+weeks of work to do.

 

[gearhead1]

Re: Pole Barn Attic Trusses...

I think you would find this easier, and possibly cheaper to do if you just used standard 2x6 stick building on 24" centers.

Yes, exactly. Precisely why I ended up doing a regular stick built instead of pole barn style. Mine is 36x50 with a 12’ wall to accommodate a lift later. The walls were spec’d to be 2x6. Blocking every 4’ where the OSB edges are. Attic trusses make a 16’ x 50’ upstairs for a total of 800 sq ft of storage. Truss bottom chords are 2x12’s and are 24” on center.

However, you see the potential for concentrating a lot of load on the posts. His build was a stick framed with a full concrete foundation to bear the loads. And, as the building goes higher, his was 12' interior, there is a lot of potential for side loading, where the ply/osb sheathing is adding up shear resistance. Its not there in a post frame and you'd be well served to think about some metal X-bracing all over, wherever it could be installed.

One other thing worth noting, in an already tall first floor and having an attic 2nd floor, the trusses were extremely tall and long. We had access to a telehandler/shooting boom rough terrain forklift but the geometry had it maxed out and barely able to set the trusses down before the boom would touch the top of the wall. A game of inches holding ~1500# seemingly a mile out there. It was successful though and is being finished on the interior.

That’s exactly what happens - all the load goes to the posts. The Civil Engineer has to calculate that load to ensure the post (column) doesn’t fail (probably using the Euler formula). The greater the load, the more likely a long column will buckle. This is another reason for the blocking on the stud walls in a traditionally framed structure. Think of each stud as a column, they start to twist under load before buckling. The blocking between studs gives the OSB edge something to nail to for shear, but also helps prevent twisting.

 

[climb.on]

I’d recommend talking to a truss designer or civil (structural) engineer. I ordered standard attic trusses (24” O.C.) and the loading is clearly stated on the drawing.

Exactly what I did with my 36x48x12 shop. 2' eves all around.

 

[rburke65]

Just use attic trusses that are designed for this purpose and use trusses every 24” or every 16”. Why would you use trusses every 8’ for God sake then try to figure out a way to patch in supports for a floor?

 

[Chaz]

Montana????? You mean people actually LIVE there?

( Sorry, But I get that a lot.)

 

[theoldwizard1]

Why would you use trusses every 8’ ...

Properly engineered with purlins it is acceptable. I wouldn't do it !

 

[dcg9381]

There are span tables and truss calculators for spans and specific loads.. I can maybe send you a link, but they are a bit technical.

One little "hint" - often the companies that provide framing materials have an engineering department. You send them the design of what you're trying to do and part of their job in providing materials is doing the engineering necessary to get you the right lumber.... ProBuilt comes to mind down here.

 

[Moose97]

As many others have stated, you need to either get with an engineer to design what you will need or the truss manufacturer will be able to design it. Considering your location you don't want to go cheap here and design this yourself.

 

[suavilica]

LOL