sorry I need advice on leanto build!

[BryanM]

Planning on building a leanto on the the back of my barn for some extra hay storage(gable end). The walls are 12ft. high and I want to make my leanto the width of the barn which is 32ft and go out 18ft. My question:

1. what size posts planned on 6x6every 10ft
2. what size rafters for that span? or should I look into truss?
3. what would you think the best pitch would be? the barn is 4/12?


I plan on all steel siding and may be a couple big doors depending on headers and how wide I can make the doors, havent worked that out yet.

I live in northwest ohio we do get some snow put not sure on where to find the average snow load.

I know some of you have built leantos on their barn so I thought I would ask
what you would recommend? thanks

 

[EddieWalker]

With a 12 foot wall, the pitch of the roof is going to put you well under 8 feet long before you get 18 feet out. From what little I know about snow, but more pitch you have, the better your odds are of it sliding off. The flatter the pitch, the more you will accumulate.

If it was me, I would reconsider your demensions. At 12 feet wide, you will have a 4:12 pitch to the roof with your wall height and have an 8 foot wall height. With posts on ten foot centers, you can double up some 2x10's for a header/beam and have a little over 7 feet clearance to get under the header.

If you went out farther, your pitch would be flatter to keep that same opening under the header.

What pitch do you need? What pitch is common in your area?

Here's a link to a span table that you can use to figure out what size lumber and spacing to use for the roof. http://www.wclib.org/pdfs/SimpSpanTbls.pdf

6x6 posts are more then strong enough.

Eddie

 

[BryanM]

I dont think I have too have a 4/12 pitch. As far as everyone else it ranges from 2/12 to 6/12 pitch. For me to do this I have to have at least 16ft ( I should say to make it worth my hassle I have to gain enough storage to do it so anything less than 16ft probably is not going to gain me enough.)

I can say I have not had much snow build up on my barn roof.

 

[radioman]

12/2 pitch is ABSOLUTE minumum for shed water. In the snow country- its not the pitch that matters, its the ability to handle the snowload. Everytime you have a huge snowfall and then the sun comes out, the snow gets heavy. Your 10ft post sounds a little too far apart. 6 feet max is something I rather do. I just built a "lean-to" to back of my garage and its 15ft out. I used nothing but I joists 8 inches deep for my roof. With 12/2.5 pitch and need to span onto the old garage roof, I used 22 ft spanned joists then cut up 2 by 12's into sloping angles that added the roof to over 28 ft long.

Going with trusses is one way, or just build custom joists so you have more headroom like I did.

 

[BungeeII]

I think you're going to want to maintain a 3.5 minimum. You could stretch it at 3/12.

You can place the posts however far apart you want, just plan on using taller headers at greater distances.

 

[bp fick]

Just built similar this summer. I am well north of you, but still NW Ohio is not the banana belt. I would never go lower pitch than 5/12. 6/12 even better. Lots of reasons. Snow load, water shedding qualities, shingles last a bit longer, more loft space, etc. Cost difference is minimal.

rough span length of rafters (from memory)

2x6 to 10-12' building width
2x8 to 14-16' building width
2x10 18-24' building width

These are for flat applications. With a 6/12 pitch, 2x8 would be just fine.

Cheaper than manufactured trusses. On a lean to, simple to do.

 

[deepNdirt]

Have you considered a hip type shed roof? this way you could go up higher on the barn wall, and ahve plenty of roof pitch, You would start aout just as you would with a regular leanto setting the post out the distance you want
(16 ft) at the 32 ft span, but insted of starting the roof from edge of barn to edge you would step back in off each side ( example 8-10ft. ) then set your king rafters to start at these ponts then down to the corner post, well the beam on the corner post at the higth you desire, and then level back to the barn with the beam, and rafter up to the area where you pull back 8-10 ft, ................ have I confused you yet? I can draw out things better then explaining them, the drawing is of a hip roof I found on a google search,
along with a picture of a building that has a hip roof, just imagine this building larger and push up to the barn you are wanting to build onto,
this will give you an idea of what I'm trying to describe,

 

[BryanM]

Never even thought of that. Great idea! I am going to have to investigate and do some home work on that idea. Thanks!

 

[BungeeII]

Never even thought of that. Great idea! I am going to have to investigate and do some home work on that idea. Thanks!

My guess is adding new trusses and simply extending your barn will be as cheap to cheaper than adding the hip roof. Unless, of course, you're the one cutting in the rafters for the hip roof. I could be wrong though, so your homework will certainly give you a chance to prove it.

 

[Charlesaf3]

If I went under 4/12 I'd treat it as a flat roof and cover it with EPDM. Ideally you wouldn't go under 4/12. I don't think your posts are big enough, or close enough together. And you want that roof sized for a decent snow load - ask your local inspector

Not sure if its in eddies link, but roof pitch affects what your rafters can carry. Steeper carries more.