Pole Barn Lean-to

[Kevin in OK]

We've got a 24x36 pole barn and I want to add a simple lean-to. The lean to will be 12x36. Roof slope can't be much steeper than 2/12 because the barn sidewall is only 10 feet tall. My initial plan is telephone poles or treated posts every 12 feet, a 2x6 top plate going between the posts, and 2x6 rafters spaced every 4' tied to the barn with a ledger board. Roofing is just plain old tin.

Will this be adequate? The barn is in Central Oklahoma, if that helps you with loading. I know the barn uses power poles and 2x6 trusses on 4' centers, am I mistaken in thinking that the same would work for this lean to?

Any advice is appreciated.

Kevin

 

[David G]

I do not think the 2x6 will be anywhere near heavy enough for that span. I just built one that was engineered and it has a double LAM beam on 15" span.

 

[case441]

Me and the wife cobbled this up and it survived the winter snow and wind ok.

 

[thurlow]

Everyone who answers is gonna tell you something different; (we're all basically experts) for top plate, I'd use two 2 x 6s, nailed edge to side (think angle iron), one on top of post and other on outside of post and I'd put the rafters on 2 ft centers.

 

[Anonymous-0]

I realize you need the height, but I would do nothing less than a 2 X 8 on both the front and back side of the post. I would also try to find some with a good crown, which would help for any sagging down the road. Easier to build a little stronger in the beginning than to fix later.

 

[david - or]

Yes, you are mistaken. A truss is a much different animal than a simple rafter. The 2x6 rafters are way too light for a 12 foot span,especially for 4 feet on center.

The 2x6 "top plate" doesn't work either. You'd need a header or ledger board oriented vertically, not a "top plate" oriented flat, and a 2x6 is too small even as a ledger.

 

[Leroy]

Make a box on top of the posts with 2 x 8 both inside and out and a 2 x flat on top and go with plain rafters and with a 2 x 6 go every 16" with sheating boards on top to fasten the tin to. If yoy go wider than the 16" then you will need to go to a 2 x 8 rafter and for the 2 x 6 it would be better to go with a 12" or 14" rafter spacing.

 

[Germ]

Does your county issue a code or guide book on pole barns?

In my area, post would have to be 6x6 8 foot on center. The main girts for the rafters would be 2 - 2x12, 1 on each side of the post, bolted with 2 - 1/2" carriage bolts. Rafters for a 12' span would be 2x10, 2 foot on center as well as your header on the existing building. Minimum pitch is 4/12.

 

[Kevin in OK]

David, you are correct. A vertically oriented header is what I intended.

After reading everyone's inputs, is the structure in the link underbuilt?
Lean To

 

[charles todd]

I built a 24' x 33' "lean-to" shed off of my shipping container shop. I used 6" C channel and 6" purlins. I skinned the roof with 29 ga. ag panel. I plan to skin the sides with 29 ga. ag panel as well soon. The sides face dead north and south. The front is dead west.

With the exception of bolting the posts to the channels, the rest is welded. I welded all purlins into the channels. One day I may move this building and I will only loose about 1' of width once I cut loose from the channel. I will buy new channel pieces and it will be a 24' x 32' instead of 33'. The goats will like it for a new loafing shed!

This is what I did last year. The cost including 4x6 posts was about $1300. I figured it was not bad for 100% new materials minus the 5/8" power pole bolts, square washers, and nuts provided by my neighbor.

Good luck,

CT

 

[Leroy]

Yes, very underbuilt. And it only looks to be about 8' wide and going from 8' to 12' will more than double the strength needed. And where you are at acording to the news this past year you had a lot more snow than we had here in Ohio. My shed roof was 2.1" slope per foot and that is all I could work on, anymore is too steep for me altho you cannot get a contractor to build with less than a 3.0" per foot of slope, normall is 4" per foot so being that flat it requires bore strength in the rafters than a steeper slope for a snow load.

 

[David G]

I see a 2x4 stud wall being built inside the main poles on the pictures. That would help support the span. The constraints will vary based on the snow load, so your local building codes should be what you base the design on.

 

[Zachary Hoyt]

When I built a small barn in 2008 I had an addition on the side to hold the sawmill. I have an 18' span between posts where the mill is, and a built-up 8x12 beam spanning it. The rafters are spanning about 12-13' and are rough cut 2x8. There is a big difference between rough cut and KD planed like you get from the lumberyard. Inside to hold up the loft I used two 10" mobile home frame I beams. I'll put up a couple of pictures. For a reasonable span like 8-12' I would think 2 2x12 planed or 2x10 rough would be okay, but I am in the snowbelt in NY where we have less wind than you probably do.
Zach

 

[Chris in SK]

You need to build it heavier if you have any type of snow load. I built just about the same size lean to as you are proposing on one side of my barn last year, and plan to do the other side this year. I used posts on 8’ centers. I made the posts with three laminated 2 x 6’s nailed and glued. I used 2 x 12’s for the headers, and 2 x 6’s for the rafters on 16’’ centers. My roof slope is 2 / 12, so I doubled some of the rafters and built ½ truss type rafters off the posts. When I build the other side, I think I will go with 2 x 8 rafters. I used 1 x 4 purlins, and 2 x 4 girts, and 29 ga metal for the roof and siding.
Chris

 

[bc]

A 12' spread for telephone poles isn't a problem. They are huge. 5 posts of 3 laminated 2x6s would work. I would use 2x12s, one on both sides of your telephone poles along the side wall to support your ceiling joists with the inside one a little higher according to your roof slope. Same for a ledger board on the present side. You can put the inside one in last after the joists. Without checking, you are only dealing with wind and snow loads of 30 psf. Unlike floor joists also supporting a floor and ceiling plus live loads. 2x8's every 4 foot may work for the ceiling joists with 2x4 purlins every 2' along the roof for screwing down your roof sheeting. Purlins every 2' on the walls as well.

Best thing to do is go to your full service lumber yard where they sell these kits all the time. They have programs or already know the engineering on these. You have to get past the kids at the register first.

 

[charles todd]

Leroy, I do not know if you were replying to my post or others? If so, yes we had 8" in Natchitoches, LA this year in one day. It broke state records. Last snowfall was in 2000 and it was about 1". As for wind, I am +4 hours (200 miles) from the coast, so winds are not that bad. It looks under built, but it is much stronger than it appears. After all I am an Engineer and I would not have been on top screwing the roof sheets on something I'd fall through.

Side note, the barn pics I saw looked good. I like the board and batten style siding and that barn presents it proud!

Take care guys!

CT

 

[Leroy]

My responce was to the orignal poster in OK.

 

[Kevin in OK]

Yeah, I shoveled more snow than I ever have in my life. We had 14" of the stuff in Oklahoma City. All the outbuildings were still standing, though.

 

[Steven-Id]

If your poles on the existing building are 12' apart also, you could use something like a 2x12 on each end and 1 on each side of your center post. Then put 2x8s for your purlins between the 2x12s and just screw your metal to the 2x8. I would check with the local building dept. for loading requirements. Here we have to meet a 30# snow load so the county requires 2x8 purlins for a 12' span. You may be able to use lighter materials, but if your going to build it don't build so light that you regret it later.
Steven

 

[ChrisinMO]

I added a lean-to to our hayshed late this last
winter. The poles were 16' apart and 14' away from
the hayshed wall. We used 2x10s at the hayshed for
a ledger board and doubled 2x12s at the poles to
set the rafters on. The rafters were 2x8s spaced
2' on center. For purlins I ripped 16' 2x6s in
half and they are two feet apart. That and the
roofing were quite a bill, but the roof is almost
flat (a little less than 2:12), so I wanted to err
on the side of strength.

Not that I'm any kind of carpenter, but 2x6s
spaced 4' apart seems kind of light for such a
flat roof.

Just my 2cents.

Christopher