12x24 lean-to

[bigballer]

i am in the process of planning a free standing leanto addition to the end of my pole barn and need some advice. the size will be 12x24, 24 being the "long" side. one end should be open i'd like the option to enclose the long side and the back end eventually. i'd like to stick with 2x8 joists and according to the span calcs have found that spaced 16" apart 14' lengths should be fine. hemfir is the primary type of wood here. i plan to cover with metal roofing using 1x2 purlins. wondering what size posts i should use and spaced how far apart? also what size should the end beam be and how best to attach to posts? i'd like some overhang if possible.

 

[scesnick]

I wanted to do the same thing to my pole garage to put all my implements under. I did the research and decided that is would be WAY easier and cost effective to buy a metal carport and sit it right beside my garage. You can get and 18x21 carport installed for $695 in my area.

 

[Army grunt]

I would use 3- 6x6 up rights. 2- trippel 2x8 12 ft with diagonal bracing sandwiched in between the 2x8s this will cut the 12 ft span down.
Army Grunt

 

[BeezFun]

wondering what size posts i should use and spaced how far apart? also what size should the end beam be and how best to attach to posts? i'd like some overhang if possible.

You're carrying almost no weight so 4x4 posts would probably be fine from a structural standpoint, but if you have the risk of things banging into them (like horses or tractors) or eating them (like horses), you should probably go 6x6. I'd space them 12' since that works out good with a 24' side and allows you to easily make 12' stalls/garages later if you want to.

When you say "end beam" I assume you're talking about the header over the open side. How you do the attachment depends a bit on how much slope you have on the roof. If it's sloped a lot you need to do something to resist bending the header in the weak direction (toward your existing barn). And you need to attach it to the posts in a way that resists in that direction.That can be either a horizontal element attached to the back wall of the structure, or you could make truss elements with the right pitch that sit on top of the header. If the roof were flat, you could just sit the header on top of the posts and secure with a scab on two sides, or using one of the metal joist hanger type products that are made for those connections.

I'd encourage you to make a simple sketch and post it, that will make it easier for folks to comment on what you're planning. For example I assume it has sides but can't tell for sure. So you need some kind of diagonal bracing in that direction. Also if you have no back wall and no front wall, you need a LOT of diagonal bracing in the long direction. On the front side you might consider 2' wide walls on the front side, reducing the open area to 22' but that would probably provide the required diagonal bracing.

 

[bigballer]

here is a rough sketch, the back and side could eventually be enclosed but for now i just want a roof. it will be used for tractor parking along with maybe an ATV, lawnmower, etc. i would like the roof sealed on the barn side so water would not leak down into it along the barn wall. i will only be able to get into it with my tractor from the front as clearance as no room around the back side due to a retaining wall and the a ditch along the "side". the high side will be about 9' high and the low about 7-1/2'.

 

[BeezFun]

OK, picture helps. Diagonal bracing is an issue. I assume you plan to put the posts in the ground below frost line, so that helps with diagonal bracing. If they're 6x6 that's probably enough to take the lateral load under heavy wind. But you probably still want to add something in the corners if you can, like either plywood or steel cable. Make sure to use hurricane straps to hold the rafters down.

For the headers I think double 2x8 with plywood core. You could also use metal. If you put 1/2" steel plate between 2x8s (called a flitch plate), that would really be a solid header. But it's a bit of a pain to fabricate. They probably need some bracing at the midpoints in the weak direction, could use wire rope from the opposite corners with a turnbuckle for that.

I think I'd use a heavy 2x6 ledge on the 6x6 under the header, and throughbolt the header to 6x6.

I think the other poster who suggested one of those metal carports had a good idea. Not sure it will allow you the access you require though, they depend on diagonal metal bracing on the long sides. You can buy those at Menards, anchor it to the ground and you're done. Might have to add a gutter on the barn side to get the water away.

 

[bigballer]

i hadn't conisidered one of the carports but after pricing out a 12x21 with 9ft legs the cost would be comparable. the advantage being it would go up much quicker and could resell it if i ever decided to. i'll have to check around to see if anyone offers a 24' model. thanks for the replies.

 

[forgeblast]

Check ebay too, I bought one for 150.oo cheaper then I could from a local company and they worked with me on the size. It was an outfit from NC.

 

[HoustonBrama]

I did exactly what you're wanting to do. I added a 12' lean at the side of my barn (24' long). I ran a 2"x10" header along the barn side to attach the roof rafters to the barn. I put 6"x6" posts in the ground (spread 12' apart). I used (2) 2"x8" doubled up and bolted to the posts for the other end of the rafter supports. Used 2"x6" rafters spread 4' apart and 2"x4" perlins spread 4' apart. Layed down metal roof. The lean to has been there for more than 8 years and looks like it was built yesterday. It was cheap (about $500 then). I get really high winds where I live and have had no issues. Snow load here is pretty minimal so you might have to tighten the perlin and rafter measurements up. Hope it helps!

 

[Hughman]

I built a lean-to like this years ago off the side of my house to cover a boat. 28x14, one side lagged into the house, other side built of 3 4x4 posts and 4x6 beam, 2x6 rafters and metal roof. No wind or weather problems to consider so it worked well. Later tore it down to park an RV that was too tall for the lean-to.

I ended up covering the boat with a panther creek car port (available from the big orange box or sprawlmart). The car port started out as a 12x20, but I added a length kit (+5') and height kit (+1' or 2') so it ended up 12x25. Much easier to build and move later on. You can also add side walls and end wall so it is only open on one end.