Building a lean to roof

[pricefarm]

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 ?

 

[sstterry]

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.

 

[BFE]

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.

 

[JMJ Farms]

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.

 

[Dsth]

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.

 

[bird dog]

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.

 

[wbvs58]

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

 

[pricefarm]

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.

 

[JMJ Farms]

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.

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.

 

[pricefarm]

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

 

[Hoover]

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

 

[JMJ Farms]

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.

 

[pricefarm]

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.

 

[JMJ Farms]

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.

 

[BFE]

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.

 

[BigBear56]

Wow based on these responses I don't know how my barns made it this long lol. I have 2 such roofs that are hip roof add ons. Both have low slope. The first section is 36' wide by 18' deep. That one has (3) 6x6 posts with 2x12 headers on both sides. The roof beams are 2x12 that are spaced 8' apart. Low slope, central Ohio, built in 1954. With a 6' level, it's level and plumb all the way around.

The other is 30' wide by 15' deep. (4) 4x4 posts on each end with 2x10 headers. 2x6 roof beams spaced 2' apart. Built in early 2000's. I have not put a level on it but it appears fine.

I always overbuild and would use the largest lumber available to build anything. Big posts, joist hangers, hurricane clips the whole 9 yards. FWIW

I think your 2x8s on 16" centers would be fine if you had 2x12 headers with 6x6 posts to carry the load

 

[Dave]

The loafing shed I am rebuilding is over 40 years old. It had Juniper posts about 4 inches diameter on the top. Lodge pole pine about 4 inches for headers. And 14 foot long lodge pole rafters about 3 inches in diameter on one foot centers. Tin roof with about a 3/12 slope. We don't get a lot of rain or snow but some years we do. In 2016 it stood through 3 feet of snow.

 

[Hoover]

Bigbear, back in the 50s I would believe that, they had the lumber to build, the lumber these days isn't what it was, kiln dried lumber is more prone to snap as apposed to the air dried in the good old days.

 

[BigBear56]

Bigbear, back in the 50s I would believe that, they had the lumber to build, the lumber these days isn't what it was, kiln dried lumber is more prone to snap as apposed to the air dried in the good old days.

For sure. I'm pouring a concrete retaining wall on one side of this barn and the posts below grade are as good as new.

 

[Dave]

I have started working on putting a new roof on the loafing shed. Any of you construction type who think poorly of my job please hold your comments. I am in strict compliance with the Eastern Oregon Ranch Construction Manual. We do have standards you know.