Building a lean to roof

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pricefarm
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Building a lean to roof

Post by pricefarm » Wed Aug 12, 2020 10:18 pm

Iam wanting to build a lean to shed over part of my corral where we work cows. Wanting to go 20 ft long and 18-20 feet wide. I don’t want any post in the middle. On the ends post will be on 10 ft centers. What size lumber should I use for the rafter? Would a 2x8 span 18 ft if I put them on 16” centers ?



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Re: Building a lean to roof

Post by sstterry » Thu Aug 13, 2020 4:31 am

What kind of snow load will you expect? I may be mistaken, but for some reason I have in my mind that you get more snow in your area than most of the other upper South.

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Re: Building a lean to roof

Post by BFE » Thu Aug 13, 2020 6:01 am

My dad's machine shed has 20' lean to's with the posts spaced 20' apart so we can pull large equipment in and out for the sides as well as the ends. It's built with 12-14" laminate rafters, I'll have to look to tell you spacing and the rafter size for sure.

I'm going to say that 2x8 lumber spanning that distance is not sufficient. The old rule of thumb is 1" of 2x lumber per foot of unsupported span, so 2x10 for 10' span, 2x12 for 12' span and so on.

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Re: Building a lean to roof

Post by JMJ Farms » Thu Aug 13, 2020 7:05 am

If you just want (4) posts total then 2x8s will work for a little while BUT are not sufficient. I would recommend (4) 6x6 posts and either a doubled 2x12 band on front and back, with the outside band notched into the post, with 2x12 rafters on 24” centers (OR) LVL OR TJI bands and 2x12 rafters. I AM NOT accounting for any snow load. That’s just rain. Whatever you do make sure you bolt, screw, and hurricane strap everything you can. A shelter is a giant kite.
Until we remember that the left wing and the right wing belong to the same bird and we come together as a nation then this country is in for more turmoil - Jogeephus

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Re: Building a lean to roof

Post by Dsth » Thu Aug 13, 2020 9:20 am

I built a 36 foot long by 14 foot wide lean to a few years ago with 6x6 post 10' apart and 2x10s for rafters with 24" centers. mine was attached to the side of an existing building and enclosed on the other three sides so flying like a kite was not a concern for me. my local lumber yard drew up the plans since I consider them as much more knowledgably than me. We do get a considerable amount of snow here also.

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Re: Building a lean to roof

Post by bird dog » Thu Aug 13, 2020 2:58 pm

What you use for roofing will also matter. Get a good lumber yard to size up the members for your area. It might be cheaper (and better) to go with steel.

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Re: Building a lean to roof

Post by wbvs58 » Thu Aug 13, 2020 7:16 pm

Light weight steel C section like 200x75 (8"x3") will do it easy and is much lighter than what you would need in timber.

Ken

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Re: Building a lean to roof

Post by pricefarm » Thu Aug 13, 2020 8:32 pm

JMJ Farms wrote:
Thu Aug 13, 2020 7:05 am
If you just want (4) posts total then 2x8s will work for a little while BUT are not sufficient. I would recommend (4) 6x6 posts and either a doubled 2x12 band on front and back, with the outside band notched into the post, with 2x12 rafters on 24” centers (OR) LVL OR TJI bands and 2x12 rafters. I AM NOT accounting for any snow load. That’s just rain. Whatever you do make sure you bolt, screw, and hurricane strap everything you can. A shelter is a giant kite.
I don’t think I explained myself right. Here is what Iam wanting to do.


Image

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Re: Building a lean to roof

Post by JMJ Farms » Thu Aug 13, 2020 8:45 pm

pricefarm wrote:
Thu Aug 13, 2020 8:32 pm
JMJ Farms wrote:
Thu Aug 13, 2020 7:05 am
If you just want (4) posts total then 2x8s will work for a little while BUT are not sufficient. I would recommend (4) 6x6 posts and either a doubled 2x12 band on front and back, with the outside band notched into the post, with 2x12 rafters on 24” centers (OR) LVL OR TJI bands and 2x12 rafters. I AM NOT accounting for any snow load. That’s just rain. Whatever you do make sure you bolt, screw, and hurricane strap everything you can. A shelter is a giant kite.
I don’t think I explained myself right. Here is what Iam wanting to do.


Image
6 posts simplifies things. A double 2x10 band on the front and back, with the posts notched to accept the outside band, will carry to load. 2x8s would probably be sufficient but I tend to overframe, especially when I’m building pole barns or shelters. 2x12 rafters on 24”, 36”, or 48” will work. Depending on snow, a 24” may be preferable. I don’t have to deal with snow in GA so I don’t have any experience there. 2x4 lathes on 24” or 30” centers is the norm here. Most important component is two wind braces screwed on the bottoms of the lathes running on opposite diagonals from front center to rear corners. Nails may be sufficient but screws are better. Straps and bolts anywhere you can get them and you should be good. Hope this helps.
Until we remember that the left wing and the right wing belong to the same bird and we come together as a nation then this country is in for more turmoil - Jogeephus

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Re: Building a lean to roof

Post by pricefarm » Thu Aug 13, 2020 8:54 pm

Ok I was going to go 16” centers on the rafters using 2x8s and then 2x4 laths on 24” centers. Think that will work ?

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Re: Building a lean to roof

Post by Hoover » Thu Aug 13, 2020 9:02 pm

I build for a living here in southeast Kansas, I’m not sure where you are but there’s a couple questions that need answered.
1. Location and snow amounts
2. Roofing material, I assume metal
3. Projected roof pitch, the flatter the roof the more deflection in the members.
If you was in my area and wanted me to build this, let’s say you want minimal pitch, 2/12.
I would knotch in a 2x12 split only on the post, then double it up between post. I would then use 2x10s with zero cracks and very few knots as rafters, 2x4 perlins and metal it. But that’s here

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Re: Building a lean to roof

Post by JMJ Farms » Thu Aug 13, 2020 9:10 pm

pricefarm wrote:
Thu Aug 13, 2020 8:54 pm
Ok I was going to go 16” centers on the rafters using 2x8s and then 2x4 laths on 24” centers. Think that will work ?
2x8s will work for rain if you put them on at least a 3/12. But they will sag.
Until we remember that the left wing and the right wing belong to the same bird and we come together as a nation then this country is in for more turmoil - Jogeephus

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Re: Building a lean to roof

Post by pricefarm » Thu Aug 13, 2020 9:18 pm

So better go with 2x12 rafters then. We get some snow but usually not to much 6-8” would be a blizzard here. Usually on a couple inches at a time.

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Re: Building a lean to roof

Post by JMJ Farms » Thu Aug 13, 2020 9:26 pm

pricefarm wrote:
Thu Aug 13, 2020 9:18 pm
So better go with 2x12 rafters then. We get some snow but usually not to much 6-8” would be a blizzard here. Usually on a couple inches at a time.
I think you’ll be much more satisfied. 2x10s minimum.
Until we remember that the left wing and the right wing belong to the same bird and we come together as a nation then this country is in for more turmoil - Jogeephus

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Re: Building a lean to roof

Post by BFE » Mon Aug 17, 2020 6:43 am

Image
20 ft lean to 6” posts on 20’ centers. 2x6 purlins on 2’ centers. Rafters are 12” laminate. Header is a 2x12 and a 2x16 laminate. We are along I64 so we probably have similar snow load. We get big snow about every 3-4 years but most years very little.
Edit rafters are 5’ spacing.
Image

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