16x24 lean-to on back of pole building

[bigballer]

i am in the design stage for a covered storage area off the back of my pole building. i wanted to run this by the group to see if my design makes sense. the lean-to will be built on the back of the building the existing bldg is 24x40 so my plan is to extend the lean-to another 16' and keep the 24' width. i originally planned to attach one side of this to the existing bldg using a ledger board and connecting to the existing framing through the metal siding but now i think planting posts right next to the building will be a better idea. the existing bldg is over 20yrs old and i don't want to compromise it in any way.

so the plan is to set 4x6 posts 8' apart along the bldg and another set of 4 at the 15'6" mark at the outside. i will then use 8' lengths of 4x6 (on edge) to span over the top of the posts to make the beams (on both ends) connecting them to the posts using the T and L ties. for the rafters I will use 16' 2x8's (or 2x10's) 16" OC setting them on edge on top of the beam and connect them to the beams using hurricane ties or some other simpson connector (exact connector tbd). this will give me 6" of overhang on the outside edge and a few inches of overhang on the bldg side. to allow me to lay the metal roofing down, i will then attach 1x4's to the rafters so i have enough points to screw the roofing down. i will then seal the gap between new roof and existing siding with flashing and silicone.

How does this sound? if you have built something similar and can post pictures of it, that would be great!

 

[rural2]

Just did something similar (10'X22'). Didn't attach to existing through the siding though and beefed up an existing girt to make a header (10'-9" span) instead of adding new posts at the existing bldg. The new header is is just another 2X6 on edge below the existing girt with 3/4" plywood laminated on both sides to tie it together and minimize vertical deflection. Used hangers to attack the joists to the header. Sorry no pics.

 

[bigballer]

my reason for not wanting to attach to the building is that the truss is actually on the outside of the post, thus no real beam to attach to. Is this a "normal" design for a pole bldg or was this done by a DIY'er? In order to connect my ledger for the lean-to, what would be the best way to secure it?

You can see in the pic's what I am talking about:

Wide Angle end of inside of bldg. my lean-to will be on the other side of this wall.


End of Truss, supported on Post by way of a 2x6 block:


Middle of Truss, no blocking, attached directly to center post:

 

[rural2]

Looks to be typical "kit style" pole barn construction... You could use either method, however unless the addition is solidly attached to existing you may see connection issues from movement down the road and silicone is almost always a bad idea. There are several ways to do it w/either shed or pitched roof. I assumed from the original post you want a shed roof??? Since you already have an existing 1/2 truss (very good thing) on the gable end, IMHO it's overkill adding additional posts and beams for the connection, especially when your keeping the center post.
Personally, (for a shed roof) I would remove the existing siding, establish a height for the new roof that works with existing roof height and pitch, head it off by incorporating the bottom chord of the existing half truss as already described or similar for the connection, use the post and beam method or a double 2X8 assembly for the new beam, set the new roof joists at the connection in hangers and skip sheet, hurricane clip, etc. as you already described, plug the existing gable end w/the top part of the siding you removed, flash under that and over the new roof (skip the silicone), should be able to use the remaining siding you removed to side the new wall if wanted. Install new girts, remainder of new metal siding and trim. Wala, new addition! Access the new area however you planned.

 

[bigballer]

my plan was to do something like this: http://www.tractorbynet.com/forums/...1068525224-adding-lean-337373-lean-framed.jpg

I had considered doing the way you describe (extending the roof line, etc) but that end of the bldg is taken up by 2 horse stalls that I can't move. The lean-to plan seemed much simpler, I know the look isn't as "clean" but it's off the back sort of out of the way and it's ok to be seperated from the rest of the bldg.

 

[rural2]

Nothing wrong w/a shed roof, thats what I just did as a matter of fact.
In that pic it appears to be a single 2X8 nailed to the posts for a header instead of a 2X8 w/corbles on each side of the posts, also no mid-span blocking (maybe these were added later???). I don't know how he is making that ledger connection to existing solid without crushing the ribs of the siding either. Also not sure how that particular connection could be effectively flashed. Here on the rainy side of Oregon that connection leaking every time it rained would be a problem (about five or six months out of the year anyway). I also prefer more pitch to a metal roof, 3:12 or better seems to be pretty standard for metal roofing. Gotta remember there are a lot of exposed screws holding the metal down and a person doesn't want any puddling around them.
Again and JMHO, for the few x-tra hours labor I would remove the existing siding... But that's just me