Possible Pole/Monitor Barn Build Idea

jclaudii · Nov 9, 2015

I am thinking of building a barn or shed soon and would love to have one that was pleasing to the eye as well instead of a metal box. I live in AR so snow loads are very little, but either way I think I will be more than adequate as many a similar pole barns have stood for decades. There are a few similar barns built this way on this site and other popular forums for DIY garages and projects like this but I have changed a few things. I am thinking about a 35 x 30 foot with a height to top of center poles of 17 feet (total height to top of ridge is about 20 feet). Center bay height to bottom of beam is 9 foot and side sheds are 7.5 feet tall. I am not fixed on 9 feet for the center yet as I could always raise it up a bit if I wanted more height before I start. Center is 13' 6" wide and side sheds are 9.5' wide. Each "bent" is roughly 9.25' apart for a total of 5 bents.

Now here is the kicker where I am completely over my head and may have to scrap this idea, but I wanted to leave one section of supports out to make a clear span on one end of about 20 feet. This would allow room for a lift(someday) and a lot nicer working area in one section. So as you can see in the image, I did not use regular lumber here, but put a beam in, could be a wood lam beam or an steel I beam, I am not sure here. If this idea would be too costly or need to get an engineer then I may scrap it and just live with it. there would also be no floor above this section, just open to the ceiling or a smaller storage area that is built up close to the ceiling for junk (think attic).

I mainly wanted to show the structure of the barn, only thing not shown on here are purlins. I was thinking of pouring 8-12 inch tall footings dug out a few feet instead of burying these poles. I am thinking of utilizing local wood that I can saw up roughly with a chainsaw mill Main center supports here show to be an 8x8 actual dimension with 4x4 actual dimension for the side shed uprights. Plan is to utilize gravel bottom until we make more for a concrete slab.

I am seeking feedback on this way before I ever get around to cutting or building anything so please chime in

Thanks,
Jclaudii!

KennyG · Nov 9, 2015

I see what you are trying to do and I think it's possible, but you will need to do some calculations for those beams. My guess is they are going to be very large, probably engineered timbers to pick up all that roof load. You're outside the normal configuration here and you will have to sum up the structure loads that are going into the beams and then use beam tables to size them. For a 20 foot span, I'm guessing you won't have to go to steel, but it might be an attractive option. You will also need to look at the posts and make sure you have plenty of margin.

It's been a while since I looked a structure like this, but you might look at making the second story a stud wall structure. That would distribute the load over the beams more and avoid putting the entire load at the center point on the beam. Calculationally it doesn't make a difference and the beam stress would be the same, but I would rather not have the point load, especially using wood.

jclaudii · Nov 10, 2015

Perhaps I could put a regular support on one side and just use a structural ibeam / versa-lam (never priced but I'm sure it's super expensive for one beam), or have an engineered beam specked out and make my own. If I do just one bay it would give me a 25x20 open work area and still have enough room for a lift if I needed it.

Just calculating some numbers under each end of the 20 foot span I would have to have at min 30"x30"x12" footer for the post and possibly a piece of pipe for extra support.

Now I've read some timber framing, enough to be dangerous, and I will include the 45 degree bracing to help here as well.

Jim Timber · Nov 14, 2015

What about using plywood (glued and screwed) to brace the bottom section of the wall across the clear span? You'd effectively make a large beam but you could build it in place.

ultrarunner · Nov 15, 2015

Could you make the center bay wider and not have to engineer?

The monitor style is my favorite style and I have played around with different configurations...

For my site I was going to go with a 16 or 18' wide center with 12' lean tos...

Barnbuilder · Nov 15, 2015

I built one several years similar to that. Had a partial loft in center. It was 20' wide with 12' sheds. I think I had to use triple 16" LVLs. Would be happy to check when I get home. I have pics also.