Ledger over hard foam

[Mancelona Man]

Good Afternoon

I’m adding a lean to on my post frame building.

Couple of questions:

Can I bolt the ledger board direct through the metal and 1” hard foam to the existing 4x6 post or should I remove the layer of metal and foam and have wood to wood?

I’m in the snowbelt of Northern MI. We have a 60/70 psf snow load:

Will I be ok with 2x10-24oc or should I go 2x12-24oc with a 12 foot span (2 or 3 pitch).

I would prefer 2x8 but I think those will be a little thin with the snow loads

Thx

JR

 

[firebirdparts]

You don't get to put a ledger board at all on a post frame building. There's nothing there to hold the weight of the roof up. You'll have to consider that a beam sufficient to hold the roof up. I mean "ledger" assumes there's something like planet earth behind it. I apologize if you already knew that.

I am not really professionally qualified to say no to the attachment over hard foam, but I certainly would not do it.

 

[Mancelona Man]

You don't get to put a ledger board at all on a post frame building. There's nothing there to hold the weight of the roof up. You'll have to consider that a beam sufficient to hold the roof up. I mean "ledger" assumes there's something like planet earth behind it. I apologize if you already knew that.

I am not really professionally qualified to say no to the attachment over hard foam, but I certainly would not do it.

There are existing 2x12’s attached to the 4x6 post that I would attach the ledger to.

 

[Mancelona Man]

This is the inside of the building

 

[jack stand]

Has this building been through a winter?
I don't mean to derail the question but I don't see much of anything substantial fastening that inside portion of the 2x12 "beam" to the post or the truss blocking.
I like to have at least 10-12" of drop between the existing soffit and the new roof. You need room to properly flash the new roof and install closure strips. Disregard this if you only have a fascia board and no overhang.
You didn't mention how long of a span you're rafters will have as your "ledger" will be supporting half of the snow load and it needs to be considered in your design.
You can do what you're proposing, but you're support may involve engineered lumber to support it.

 

[manwithtools]

Will I be ok with 2x10-24oc or should I go 2x12-24oc with a 12 foot span

You didn't mention how long of a span you're rafters will have

Looks like OP said 12' span...

 

[Mancelona Man]

Has this building been through a winter?
I don't mean to derail the question but I don't see much of anything substantial fastening that inside portion of the 2x12 "beam" to the post or the truss blocking.
I like to have at least 10-12" of drop between the existing soffit and the new roof. You need room to properly flash the new roof and install closure strips. Disregard this if you only have a fascia board and no overhang.
You didn't mention how long of a span you're rafters will have as your "ledger" will be supporting half of the snow load and it needs to be considered in your design.
You can do what you're proposing, but you're support may involve engineered lumber to support it.

It has been through over 25 winters. She has no problems holding snow. I do clear it off a few times each winter

Theres a 1 ft overhang on all sides

 

[manwithtools]

I think wood to wood is best. It would also allow proper flashing to avoid water leaks. It's more work for sure, but in the long run likely the best approach. I'd think 2x10's on 16" center would hold such snow loads, but I haven't looked at any span tables to be sure.

 

[manwithtools]

Quick question, are the rafters spanning 12 feet from the wall to the outside support beam, or is that their total length?

 

[Mancelona Man]

Quick question, are the rafters spanning 12 feet from the wall to the outside support beam, or is that their total length?

Total length.

 

[manwithtools]

So how far from the building wall to the support beam?

 

[Mancelona Man]

So how far from the building wall to the support beam?

11 feet

 

[Shoester]

This sort of thing is done all the time. Proper method is to remove the metal and insulation and attach your new 'ledger' board directly (wood to wood) to the existing structure with some lag bolts through the existing posts, then tuck some flashing behind the metal at the top of your cut.

As for sizing of the rafters for the lean-to, you can google span charts for that sort of thing pretty easily.

Rafter Span Tables

Rafter Span Tables - Use these tables to determine maximum rafter length.

www.mycarpentry.com