Lean-to shed and snow loads

[Kevin B.]

I'm putting a leanto off the back of the garage. Twelve feet across, seven feet deep, roughly a four to one pitch tho I don't have that part nailed down (hah!) yet. I penciled in three 4x4 posts along the twelve foot side, with a 2x4 nailer. Now I'm thinking I'd love to delete the middle post and just have the two corner posts - will my 2x4 nailer hold up when it gets several inches of snow on it this winter? Go to a 2x6? 4x4?

I'm feeling a 2x6, but I really have no idea what I'm doing.

 

[N-Smooth]

I built a 4x8 one with all 2x's and it's been solid for several years FWIW

 

[Gravy]

I have no practical input, but I want to see pictures for ideas.

 

[Spork]

Stupid math (warning pulling numbers out of the air).
7x12 = 84 square feet
6" snow storm = (.50) = 42 cubic feet of snow
using numbers from - http://www.monroect.org/filestorage/467/469/698/750/SNOW_WEIGH_PER_CUBIC.PDF
light fluffy snow is about 7 pounds per cubic foot = 294 lbs (can get up to 20lbs per cubic foot) = 840lbs

Personally I'd be more worried about your headers than the 4x4 support posts. As you remove the center post you will need to scale up the horizontal header wild guess at least a pair of 2x8's nailed together if not a set of 2x10's.

Honestly if it were me I'd check what metal square tubing costs for your uprights so I wouldn't have to worry about the wood rotting and weld some U brackets to the top that your header would slide into and drill/bolt them in.

 

[Kevin B.]

Stupid math (warning pulling numbers out of the air).
7x12 = 84 square feet
6" snow storm = (.50) = 42 cubic feet of snow
using numbers from - http://www.monroect.org/filestorage/467/469/698/750/SNOW_WEIGH_PER_CUBIC.PDF
light fluffy snow is about 7 pounds per cubic foot = 294 lbs (can get up to 20lbs per cubic foot) = 840lbs

Personally I'd be more worried about your headers than the 4x4 support posts. As you remove the center post you will need to scale up the horizontal header wild guess at least a pair of 2x8's nailed together if not a set of 2x10's.

Honestly if it were me I'd check what metal square tubing costs for your uprights so I wouldn't have to worry about the wood rotting and weld some U brackets to the top that your header would slide into and drill/bolt them in.

Thanks for the math. I got to looking at the roof over my patio, it's 28x17 or so, with four 4x4 posts along the long side and a pair of 2x6s sandwiched together for the nailer (header? Maybe I don't know the right word). That's seven feet between those posts, but a lot more potential snow load (and less pitch than what I'm building now). I'm gonna go with a 4x4 on each corner and pair of 2x6s for my own nailer and I'm pretty sure that'll be overkill. The way it's designed it won't be difficult to add a post in the middle later if I have to.

Pics once I get it put up.

 

[Cascadia]

I frame full time. We rarely use 2x6 headers in any span over 5'. Usually an 8' spsn will take a double 2x10 header or a double 9.5 lvl header. I did whT thT picture looks like on my last house. It was about 15' wide and about 8' off the house. I used double 11 7/8 lvl header, a 4x4 on each corner and my rafters were 2x8. It was a 6/12 pitch.

 

[Kevin B.]

View attachment 106065

Is this similar to your idea? I'm trying to picture what you want.

Really close to that. Here's what it looked like before I went to bed this afternoon:

Treated 4x4 posts, stacked 2x6 for the header. It'll get 1x2s horizontally across the rafters, then corrugated galv on top of that. Once I've got the rafters on and I know the posts are still true I'm going to add some triangular bracing between the posts and the header exactly like your picture shows.

I frame full time. We rarely use 2x6 headers in any span over 5'. Usually an 8' spsn will take a double 2x10 header or a double 9.5 lvl header. I did whT thT picture looks like on my last house. It was about 15' wide and about 8' off the house. I used double 11 7/8 lvl header, a 4x4 on each corner and my rafters were 2x8. It was a 6/12 pitch.

2x8 rafters??? On effectively a 45* pitch? And you don't think that's overkill?

I've just barely started the rafters. 2x8s seem like a lot more beef than I'll need, but you're the expert and I'll change them up if you think I should.

 

[Cascadia]

45* pitch? 6/12 pitch means for every 12' out it goes up 6'. A 45* pitch would be a 12/12 roof. I wouldn't ever run 2x4 rafters which is what the pic looks like. I think it would sag after 1 winter. But that's just me. I think you would be ok with 2x6 rafters. 2x8 is possibly overkill but it's what I had around. For your 2x6 header, I'm thinking that will sag 1/4-1/2" just from putting the rafters and other materials on. I'm no engineer though, just going off experience.

 

[Kevin B.]

45* pitch? 6/12 pitch means for every 12' out it goes up 6'.

Thanks. I cannot math.

I'll take your advice and switch to 2x6 rafters, and watch the header to see if I need to add another post in the middle. Appreciate the input!

 

[rholbrook]

There is a post base in the picture. If you use that you should be fine with the 2x6 header. Are you shingling it? Roof it in metal so the snow slides off. I have no idea how much more it would be in metal.

 

[johngottfredson]

I have a hay barn, stables, and tool shed all with metal roofing - slow slides off pretty quick, so as long as you don't space your rafters too far apart I wouldn't worry about doing them out of 2x4's, and leaving those headers. Of course, I always oversize because I never want to worry about it...so prolly good to go 2x6's on general principles...

 

[Rock Taco]

Thread Hi Jack

Cascadia, do you have any crews available to to a house or 2? haha

Thread Hi Jack off

2x6 is more better. Spaced 16-20" on center. I would probably do at least a double 2" x 10" header.

What are your posts sitting on? is it the concrete blocks in the picture?

 

[Cascadia]

Thread Hi Jack

Cascadia, do you have any crews available to to a house or 2? haha

Thread Hi Jack off

Pm or text me. 801735264zero

Depends when it is. We have 2 years of framing but can squeeze something in here and there.

 

[Kevin B.]

There is a post base in the picture. If you use that you should be fine with the 2x6 header. Are you shingling it? Roof it in metal so the snow slides off. I have no idea how much more it would be in metal.

Metal roofing for sure, it cost a little more but I didn't want to mess with shingles.

I'm curious, what does the post base have to do with the header size?

Triple S has decent deals on metal roofing especially if you don't care about color. They have ads in the KSL classifieds often, too.

I agree about the span of the header regarding it being too small. There are some variables to figure the size. What are the specs of the lean-to?

As well, the rafter spacing and length are something that you can find tables on for the DIYer. A 2x6 at 24" spacing is recommended to 10'-11" max. 13'-5" at 16" and 14'-9" for 12" on centers. Source: wwpa.org

Thanks for the link, that's helpful. The shed is 12x7, the rafters are 8 foot. I was planning on 24" spacing for the rafters, so I'll upgrade to 2x6 and that should be about right.

2x6 is more better. Spaced 16-20" on center. I would probably do at least a double 2" x 10" header.

What are your posts sitting on? is it the concrete blocks in the picture?

Yeah, concrete piers.

The header is what it is at this point. I'll put the middle post back in if I have to.

 

[rholbrook]

With the extra post base it looks like you may have been putting a post in the middle is all I was asking. If you stick with two posts then you may need to go with 2x8 header

 

[Cascadia]

If you end up needing s bigger header you could always just nail a single 2x8 to the back side of the 2x6. It's not the ideal solution but it could work somewhat.

 

[Kevin B.]

With the extra post base it looks like you may have been putting a post in the middle is all I was asking. If you stick with two posts then you may need to go with 2x8 header

Copy. I originally intended one, but it presents logistical challenges. I may have to do it anyway.

If you end up needing s bigger header you could always just nail a single 2x8 to the back side of the 2x6. It's not the ideal solution but it could work somewhat.

For a given definition of "somewhat".

 

[Kevin B.]

Solution! Maybe? With 300 pounds of point load hanging in the middle it deflects about a quarter of an inch. I think it'll do.

 

[rholbrook]

That looks nice and stout.

 

[Kevin B.]

That storm was what i was waiting for. No deflection at all under however much that was, six to eight inches I guess. I appreciate all the tips, I think I would have underbuilt it without the input.