Attic trusses in a pole barn

Tscott · Feb 9, 2009

So the plan is to build a pole barn (40' by 60'). I had been planning to have a 4/12 pitch roof with scissor trusses. The wife asks last night if I will have attic space in the shop, and I realized that if I increased the pitch to a an 8/12 that I could get an attic truss with a rather large space above the shop.

Question 1: is there a problem using attic trusses in a pole barn? Extra stress on the timber connecting the posts?

Question 2: My desire was for a clear span shop to maximize space, but now I am wondering how to get up to this new room without building a set of stairs in the middle of the floor, or outside? retractable staircase maybe?

Question 3: The original trusses were scissor trusses to help with the Clarence for the lift, but the attic trusses will be flat bottom. This leaves me with just over 13' for the ceiling height. Is this enough for a lift? I would like to be able to comfortably lift my ford F250.

I have attached a few PDF prints of my CAD files below.

Let me know what you think

Tom

View attachment Shop side view 40' x 60' attic truss Model (1).pdf

View attachment Shop side view 40' x 60' attic truss Model (2).pdf

Tscott · Feb 9, 2009

Question 4: At this point would it be smarter to go with standard framing instead of trying to do a pole barn?

35mastr · Feb 9, 2009

Or a premade steel building.

mtwaterguy · Feb 9, 2009

How many trusses are you putting in? I have a double truss setup at every post. That leaves everything open between the posts, and solves all of your problems.

1320stang · Feb 9, 2009

I like the way Morton does their posts, they basically laminate three 2x8's together and alternate the ends so that they don't overlap. They use treated at the bottom and regular pine at the top. The middle board stops short of the top and the outer two boards capture the truss between them. Seems like a very strong system to me.

Tscott · Feb 9, 2009

Placing trusses only on posts would mean that I would need to set a post every 4' or so. The drawings i have attached show the posts spaced between 9' and 12' to accommodate doors. The rear wall of the building will not have doors, so the posts back there will be set at 10' OC. I estimated that the trusses would be set at 2' OC. The trusses will rest on 2 - 2x10" or 12" that will connect the tops of the posts, I plan to notch these timbers into the front and backs of the posts.

Tom

mtwaterguy · Feb 9, 2009

Tscott said:
Placing trusses only on posts would mean that I would need to set a post every 4' or so. The drawings i have attached show the posts spaced between 9' and 12' to accommodate doors. The rear wall of the building will not have doors, so the posts back there will be set at 10' OC. I estimated that the trusses would be set at 2' OC. The trusses will rest on 2 - 2x10" or 12" that will connect the tops of the posts, I plan to notch these timbers into the front and backs of the posts.

Tom

My posts are 12 feet apart running the width of my 96' pole barn. I have 9 sets of trusses to span that distance. All 4 of the pole barns I've built have been constructed in this manner.

Tscott · Feb 10, 2009

mtwaterguy said:
My posts are 12 feet apart running the width of my 96' pole barn. I have 9 sets of trusses to span that distance. All 4 of the pole barns I've built have been constructed in this manner.

If I was to go with attic trusses, I would not be able to have that kind of spacing. My guess is that the max I could have between attic trusses would be 2'. This would ensure the floor sheeting would not sag.

Tom

mtwaterguy · Feb 10, 2009

What I've done when I wanted storage space is use 2x6 on 16" between the trusses with a cdx floor. Never had a sagging problem. I'll take some pics this afternoon and see if that helps.

rcleaver · Feb 10, 2009

mtwaterguy said:
My posts are 12 feet apart running the width of my 96' pole barn. I have 9 sets of trusses to span that distance. All 4 of the pole barns I've built have been constructed in this manner.

You have trusses with a clear span of 96'? How do you do that? Do they use engineered lumber? Can you provide some pics?

rcleaver · Feb 10, 2009

mtwaterguy said:
What I've done when I wanted storage space is use 2x6 on 16" between the trusses with a cdx floor. Never had a sagging problem. I'll take some pics this afternoon and see if that helps.

That's a good idea. How did you determine the spacing of the joists? Do you use joist hangers?

rburke65 · Feb 10, 2009

I'm sure a truss mfg. co. will design, engineer. and build you a truss to your needs. 40foot clear span is not a problem.

1320stang · Feb 10, 2009

Are you trying to go on the cheap?

What are you putting in the attic of this building?

The wife asking about attic storage space in your shop looks like a bad omen.
I'd just say, "No, there will not be an attic, too costly."

If she needs more storage space, build her a lean to on one side with no access into your shop.

I put some OSB in my attic above my garage, big mistake, it's so full of stuff the drywall seams are cracking.

Tscott · Feb 10, 2009

rburke65 said:
I'm sure a truss mfg. co. will design, engineer. and build you a truss to your needs. 40' clear span is not a problem.

I think perhaps I worded my questions wrong. I will try to be a little more clear. I am not concerned with the ability of the truss to carry the load. These will be designed and engineered. A 40' span will be easy to accomplish.

My concern lies not with the 40' span between the front and rear posts, but with the 10' and 12' spans between the posts on the same side of the building. The gap between post tops is to be spanned by 2 - 2"x12" pieces of dimensional lumber. These 2"x12" will be what the trusses are resting on. So if the truss company specs the trusses to be 2' OC then a 10' span between the posts must support 5 trusses and any weight they contain.

On most pole barns, you only see standard truss designs without storage. Therefore, the spans in questions only support the weight of the roof and the trusses. If I go with an attic truss, then these spans (not the truss span, but the span between posts on the same side of the building) must support the roof materials, the truss materials, the sub floor, any **** sitting on the sub floor and my big *** walking around up there.

Will a double 2"x12" support that kind of load over a 10' or 12' span without sagging or failing?

Would traditional framing techniques be better suited to what I am considering?

Tom

mtwaterguy · Feb 10, 2009

Here's a couple pictures of my trusses. When I need added storage I frame a floor from 2"x6" on 16" centers. Then add osb or cdx for the floor. I have had absolutely no problem spanning 12'. If you are concerned, you may want to ask your truss company. Mine said this was acceptable.

[/IMG]

mtwaterguy · Feb 10, 2009

Sorry problem with second picture, but I think you can see from the one what I was trying to describe. Using the trusses at the post only leaves lots of room for storage.

Tscott · Feb 11, 2009

Alright, I have done a redesign and gone with flat bottom trusses with no attic space, I am planning to use a few pallet racking systems along the back wall as large overhead storage, so the attic was just going to be overkill. I need to remember to keep it simple.

Here are the PDF's of the new design

View attachment Shop side view 40' x 60' attic truss Model (1).pdf

View attachment Shop side view 40' x 60' attic truss Model (2).pdf

Let me know if you all see any glaring deficiencies. If these pass muster here than the next step will be the county for approval. I hope they don't make me get an engineered set of plans.

Tom

Jaxrunner · Feb 11, 2009

Be sure to size you headers based on you truss loads not some ones span chart. The 4' o/c truss could be a good idea but any larger o/c spacing will cost you a good bit of money with florida building code requirements. I see you are in Clay county, if you permit as owner builder they wil not require you to get sealed engineering but it is a good investment ($500-700 based on design). I can send you some pictures of some pole barns not built to code here in clay county that had to be torn down after a mild storm. I am not an engineer but worked for engineers the last 10 years. Let me know if i can help you out in any way...Mike

Attic trusses in a pole barn

Tscott

Well-known member

Tscott

Well-known member

35mastr

Well-known member

mtwaterguy

Well-known member

1320stang

Well-known member

Tscott

Well-known member

mtwaterguy

Well-known member

Tscott

Well-known member

mtwaterguy

Well-known member

rcleaver

Well-known member

rcleaver

Well-known member

rburke65

Well-known member

1320stang

Well-known member

Tscott

Well-known member

mtwaterguy

Well-known member

mtwaterguy

Well-known member

Tscott

Well-known member

Jaxrunner

Member