How would you flash a roof against board & batten siding?

[s219]

I am adding a lean-to on the gable end of my barn, but one detail I don't have worked out is how to flash the roof up against the board & batten siding. The siding and battens are 3/4" thick pine. Any ideas?

If the lean-to was going to be left open, I'd just leave gaps where the roof meets the siding, but eventually I want to close this in completely, so I feel like the roof should be flashed weathertight up against the wall.

 

[EddieWalker]

How are you attaching your ledger board? I would cut out the board and batten siding where the ledger board attaches the the framing, then slide the flashing up behind the siding, then attache the ledger board with enough room for whatever you are using for your roof.

 

[s219]

Eddie, the barn is built using pole barn construction with roof trusses above, so I have nothing structural to attach the ledger to on that gable end wall (existing poles/footings in the corners are sized to handle the roof load from the trusses on the main roof, and not designed for anything extra from a lean-to addition).

I was going to add poles external to the barn to support what's equivalent to a ledger board up against the outside wall, and those poles would then be able to hold wall girts across the new gable end of the lean-to for its siding. It's really like a separate structure built next to the existing barn as far as support loads are concerned, but it's tied in at the roofing and siding.

So this isn't a typical scenario with stick-frame construction where a ledger is bolted up to the existing wall framing and the siding is cut. I've basically got this external roof line that runs up to the board & batten siding and needs a good way to tie in and flash in.

Here's a picture of the back of the barn. The lean-to roof would tie into the gable end wall along the red line. I'd inset the lean-to a foot from each corner to make the trim and siding look neater.

 

[PsRumors]

The siding still needs to be cut and flashed. While the support is coming from the external poles the roof will cantilever over the support poles and into the existing structure. That's the only way to ensure it is weather tight.

 

[Rustyiron]

You could run a LVL, from corner to corner (where your load will go), then flash as Eddie said.
Depending on how much snow load you can get, it won't take much to hold just the roof up, and a added single post inside (or outside) the existing end wall should work to hold your 2x8-10 ledger. What's the end wall, 20'? Not all that challenging of a distance to span. How is the inside framed to close in the wall and hold up your siding? If my 20' quess is near, even some diagonal bracing from the top center down to the corners or sheathing the interior of that wall with 5/8 or better (glued & screwed) would prolly do so that you could just attach your ledger.

 

[SSdoxie]

Your gable siding overlaps the end wall siding so cut the battens of the end wall off at the red line and discard the short/top pieces. Use wide flashing to slide up under the cable siding and overlap onto the new roof.

 

[EddieWalker]

Are the interior walls finished off? Can you add support to the interior of the wall and then attach a ledger board, or beam to the structure you create inside the wall cavity? I would try real hard to avoid going with the external post idea. The smallest amount of movement over time always leads to leaks.

If you have to go with posts, I would still cut out the siding to attach a ledger of some kind for the flashing.

In the long term, would the posts bother you, or would it be worth the effort to remove the exterior siding if you can't get to the inside of the wall from the interior?

 

[Sawyer Rob]

Here's what I did on my pole barn,

Take the siding off and add a ledger board! You can then "flash", cut the siding down and put it right back up...

I think it's the best option!

SR

 

[s219]

Thanks for all the ideas guys. One possible solution is to place posts inside the gable wall, resting on the floor slab, to support the ledger. I would then cut through the siding and bolt the ledger up like it was just another wall girt, albeit taller and able to handle load unlike the existing 2x4 girts. The inside of the wall just has house wrap under the siding, so I do have access. At that point, flashing could be placed easily.

The slab was poured with thickened edges along the back of the barn to act as a retaining wall behind the skirt boards, so the slab base fill wouldn't press against the skirts. It's at least 16" thick back there. Based on that, I think the slab could surely support the load of a few posts.

I really don't want to tie into the corner poles to support the ledger, because they are not designed/sized for additional load that the lean-to would create with snow on the roof. I know people add lean-tos onto barns all the time by tacking onto the existing poles, but knowing all that went into the design of the poles and footings to support the main roof loads with 8' spacing of poles on the eave walls, I just don't feel right about having those corner poles also support new roof loads from the lean to. It might be fine, but the numbers weren't setup for that.

 

[Gary Fowler]

Here's what I did on my pole barn,

Take the siding off and add a ledger board! You can then "flash", cut the siding down and put it right back up...

I think it's the best option!

SR

This is obviously the best way to go for esthetic reasons and best water seal.
If I were concerned that the post were not strong enough to support a very minimal extra loading of the leanto, I would also be afraid that it wouldn't support the existing shed due to the engineering not sufficiently putting in enough safety factor into the design.

I wouldn't even consider putting in additional post to support the leanto at the top edge. Just put in a good foundation for the lower side of the leanto so it (the leanto) doesn't move and you will be alright.