Scoping a leanto addition to my pole building

[zuren]

I have a 20x24' pole building in the backyard that is getting a little tight. I acquired a small fishing boat last fall that I stored inside for the winter, and it became apparent immediately that I will need a different storage solution if I also hope to be able to work in that same space. I'm trying to get my head around how I should approach this so I can begin to lay out a budget:

Freestanding vs. Ledger board on barn
I know that traditional builds would have a ledger board bolted to the barn to support that edge of the leanto. Would there be anything wrong with sinking posts next to the barn, to make the leanto free-standing (supported by 8 posts rather than ledger board + 4 posts)? My dream is to tear down the existing barn and build a nicer, bigger barn in its place. If the leanto were freestanding, the barn could come down and the leanto could stay. Or is this thinking foolish? Bolt the leanto to the barn, and if funds allow us to build a nicer barn, just eat the the cost it will take to build the leanto and be okay with that loss if it needs to be demoed? Frankly, I'm not sure if a new barn will happen in my lifetime with all the other projects we have...but a boy can dream.

Posts
The footprint of the leanto would be roughly 8' by 24'. I can't make it much wider due to a tree. Due to our wet, clay soil, I'm planning to use Sonotubes with concrete and brackets to keep the posts away from the ground (some posts of the barn are carpenter ant damaged). I will be speaking with the building authority in the area, but should I be thinking about 4x4s or 6x6s? I tend to overbuild, so I'm leaning 6x6 and making everything beefy for snow load or a tree limb coming down.

In the pictures, the terra cotta dish you see in the grass is roughly 8' from the barn. As you can see, I have a few items that would do well being under cover.

Thanks!

 

[Pluribus]

For several reasons, I'd ledger board it.

1. You only have 8' of space. Putting posts in close to (even if they're almost against) the existing barn will eat up width.
2. If/when you decide to do something different, you can always just put posts under the upper side of the roof rather than demo-ing the whole thing.
3. Who knows, it might make more sense to just fix the barn posts vs. tearing that down as well.
4. Depending on how you space two separate structures, you might have water running down between them, unless you do some gutters/flashing.

Some food for thought, I'm sure others will chime in with other considerations.

 

[bczygan]

First check the zoning rules.

To get the most height, I prefer continuing the existing roof slope.

Bill

 

[matt_i]

I think you should investigate the UC4 or UC5 rating for treated timbers and buy one of those and bury it in the earth a couple of feet, set on concrete cookie or pour your own footer.

My understanding of Sonotube is that its a piling and not necessarily a moment-bearing foot like a Perma Column would be unless you stick the post in the sonotube prior to the pour.....see also the treated timber ratings....don't just buy whatever's laying in piles at the box store.

I don't see an issue with making it independent, it just adds the expense of a couple more posts rather than sharing the ones already in the main building. Just make sure your posts are all moment-bearing.

I'd also advise devising a gutter system, the splash from all that stormwater running off the edge of the roof can get your stuff wet several feet back in. And lastly, whatever you do I would advise some sort of enclosure for the underside of the rafters to exclude birds and other animals which might want to live under-roof.

 

[ezover]

only 8 feet wide, 4x4 should be fine. I went 15' and did 6x4 in the corners only because I had them on hand, I also did 2x6 for the rafters?- it was over kill, but again I had them on hand from a different project that never got going.

also I would do the ledger board, it's easy and gets the project done instead of dragging it out.

 

[mikegt4]

First check your local codes. I was surprised to learn that my neighbor was told by the building dept. that a leanto addition (ledger board) did not require a building permit while a stand alone leanto did. A pleasant surprise for them.

Will your future larger barn occupy some or all of the projected leanto space, if so there is no need to sink double the posts, just use a ledger board.