Structural design of loft in barn ?
Expresso
| Posted in Construction Techniques on
We are constructing a 36×48 barn which will have lofts running the full length of both sides (12 x48)
We are proposing to frame the loft by facenailing 2×10 ledgers against the posts (8x8s) or by lagbolting the ledgers to the posts. Can we rely on the sheer strength of the steel to hold the loft up? The loft floor joists will be 2×10, 16″ oc with 4/4 or 5/4 decking
Considering that we will be putting considerable weight in the loft (many hundreds of bales of hay at ~50 lb/bale, do we really need to have jack stud/posts under the ledgers?
Framing material is eastern Hemlock.
How do most pole barn builders deal with this? Any engineer types out there?
Thanks, Chris
Replies
No way would I go with bolting to hold up a loft - Unless it were pretty danged small.
Hay can weight up to 10# per cubic foot. Multiply that out by how high you can stack it and you've got your load per square foot of floor area. Then add about 10 PSF for dead load. Then you can start figuring out how much load you have on each post and/or beam.
I think you need to put in special posts and footings for this, along with a serious floor system. This isn't like a typical residental floor.
Someone said that Bill Clinton deserves a lot of credit for creating 10 million new jobs. Who knew they'd all be special counsels? [Rep. Henry J. Hyde]
How do most pole barn builders deal with this?
They hire and structural engineer to run the numbers.
For you look on your plans that you have for your pole barn. If you don't have any plans you do what the builders of pole barns do and hire a structural engineer.
I agree with the other responses. There's a number of things to consider, one of which obviously is the load from the bales. I'm assuming you're trying to avoid having supports beneath the loft, which is probably how most lofts are constructed. It may be possible to do that but there's not enough detail in your post to determine how you intend to frame things. For instance, you mention a ledger along the barn wall. I assume this will support one end of the loft. How is the other end of the loft (the end that is farthest away from the wall of the barn) going to be supported? I would think you'd need supports under it.
Regarding the use of bolts, that's really more of a detail that no one here can intelligently reply to because we don't have the framing plans in front of us. I wouldn't categorically say that bolts won't work. Steel is mighty strong and there's a wide range of bolt diameters to pick from out there. The adequacy of your framing design can only be assessed by someone looking at the whole framing plan and who knows what they're doing.
As an engineer, I suggest you hire one. The engineer will assess the existing structure which depends on the size and spacing of the posts (and the foundation). My guess is that unless the original structure was designed with the intention of having a loft added, it will not be sufficient to carry the additional loads. I suspect a separate, independent structural system will have to be designed for your loft.
Your local building department will require you to hire one anyways.
Sure man, just be sure and use 3"dia, grade 8 aircraft rated bolts with fender washers 16" OC.
SamT
thanks for all your feedback
chris