So, after the recent hail, I decided to put a bunch of my metal laying around to work. I am going to add a 'lean to' sort of structure to my shop. It will be attached to the shop on one end, and attached to poles at the other for support. I am making this somewhat small at 25x25 to get a couple of vehicles under in case of hail, and it's just nice to have. I want this very simple. I will weld everything. I will use my R panel roofing on top. This is basically a pole barn with no sides. I have attached a picture. What I don't know for sure is if my spans will work. I am 99% sure they will as I saw something built in town exactly like this except with 2x4, which....didn't make me warm and fuzzy, so I decided on 2x8 C style purlin. The red or brown primed stuff.

Here is a picture. Will this span be OK? My metal shops are built with 2x4 and those spans are easily 12' unsupported, so I feel like I have gone above and beyond with 2x8. Nothing is on top of the roof, there is no snow load, just R panel. I know you farmers and ranchers have done this thing before.

Disregard the 'pole' near the barn wall. It's not there. There will only be two at the ends, open all the way around.

Just because and since you are talking 25 x 25 there will be room, I would add a support in the middle of each of the three open ends. Still can get any road legal vehicle or rv between wall and middle support and open doors, as well as between outside support and middle support. Basically 6 posts making 4 squares under the roof. No posts needed on the wall side.

Jason_InfinityRoofer said:

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Thanks for the info, folks. The purlin width seemingly determines the max span. I'll ask the metal guys and then probably test like I normally do….weld it up and then have the kids and I hang on it and do pull ups, then kick the base and bang on the side and say "that ain't going anywhere".

I think it for sure will fail if you don't do the last part.

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Sorry, but this is a HORRIBLE idea...... You're supposed to say "that ain't going NOwhere". Then it should be fine

You're right. A slight breech in protocol on my end. Details matter.

You are probably good with your purlin. 5' tributary area is typical, but check the span tables. Your "rafters" (members connected to your columns) essentially have a 12'-6" tributary area and could be deficient. Think about doubling up on either side of your columns and attach to the top flange of the rafter. Or a deeper rafter. Or reducing span.

Bridge said:

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8" c purlin can span 25'. Here's span distances I've seen for each.

4" - 15'
6" - 20'
8" - 25'
10" - 30'

You shouldn't have any issues with your layout.

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User name checks out, eh?

https://issuu.com/dorvik/docs/purlin_span#google_vignette

https://issuu.com/dorvik/docs/purlin_span

For what it's worth I looked at a job today that had a carport like you're wanting to build

It was 23x23

On 8 inch purlin it was spanning 23 ft With only post on the corners on the front and back. The left and right side which were carrying the purlin weight did have a center post at 11 1/2 feet

Thanks for the info. Do you happen to have any pics of the underside of that thing? I feel like I know what to do, but a pic would be nice for confidence. I've never actually constructed anything exactly like this.

Jason_InfinityRoofer said:

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Thanks for the info. Do you happen to have any pics of the underside of that thing? I feel like I know what to do, but a pic would be nice for confidence. I've never actually constructed anything exactly like this.

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I don't but will actually be working on a project at this house so I will take some and measure the layout and email them to you