Attach lean to on pole barn

[spotco2]

I know there are thousands of threads on attaching a lean to on a pole barn, so here's another one.

Building is 30'x30' with 10' walls. The grade on the back of the building had to be built up about 2' so I have about 12' to the soffit. The top bands around the building that support the trusses are 2x10's and are lag bolted. I knew I wanted to put a lean to on, so I added another row of 2x10's below the top bands on the outside of the building before the metal was installed.

The metal siding is standard 3/4" low rise metal panels just like everybody and their brother has used on pole barns for 20 years.

The existing roof is a 4:12 pitch and has a 12" overhang with trusses 5' OC. We are in Ga so we might see 2-4 inches of snow every few years.

I would like to get at least a 15' lean to on the back of the building and possibly even a 20' if slope allows. I will cover the lean to with metal very similar to what is on the existing roof and the walls will all be open.

Couple of questions.

What's the best way to attach the lean to against the existing wall? Hangers through nailed through the metal into the pair of 2x10's? I would like to not collapse the ribs in the outside panels.

How far to space the rafters out? What size lumber for the rafters?

Since I don't have to worry much about snow load, what is the lowest pitch I can do so that water runs off the roof?

In other words, y'all design this thing and I'll build it in a couple of months!

 

[ffjosh]

subscribe...sorry I have no idea haha

 

[Fyrme]

The way I would do it, is put a 4"W x 9"L x 3/4" plywood shim every 2' o.c. in the lows of the siding. Then temp screw up a 2x10 (or 2x12) to hang your rafters off of. Then go back and predrill and lag bolt through to the 2x10 o the back side.
If you go 20' You probably need engineered I joist, or a 2x12. I think the rule of thumb is 12'-2x8, 15'-2x10, 18'-2x12. But I could be a little off on the lengths.

 

[spotco2]

Forgot to mention that I have finished off the interior of the barn and can not access the back side of the extra 2x10 that we installed.

Thanks for the info.

 

[Fyrme]

Forgot to mention that I have finished off the interior of the barn and can not access the back side of the extra 2x10 that we installed.

Thanks for the info.

3/8"x3 1/2" lag bolts will screw into them without having to have access to the boards.

 

[ADSR]

The only way to do it right is to cut the roof back and sit the new trusses on top of the existing wall. I would use metal on the new roof so you change it to a 2/12 pitch. At around 12' at the wall, you'd be around 20' long with an 8' wall at the low end.

 

[Fyrme]

LD, I'd agree if it were going to be a heavy load bearing wall, but he's in Georgia, so typically, it will never see more than a thunderstorm and flurries. With the exception of this last winter lol. If he double lags it every 24" it will be more than sufficient for what he needs.

 

[ADSR]

LD, I'd agree if it were going to be a heavy load bearing wall, but he's in Georgia, so typically, it will never see more than a thunderstorm and flurries. With the exception of this last winter lol. If he double lags it every 24" it will be more than sufficient for what he needs.

I was more worried about hight at the other end. No 2x12 or even bigger TJI will span 20 feet legally or safely. A parachord around 24" is what will be required. So with 10 walls to start with, the bottom of thr chord is already at the 8' mark inside the building. If you put the truss on top of the wall, the size won't matter as it just moves up the roof line.

 

[gungatim]

I did just this a few years ago. I will tell you how I did it, YMMV. BTW, we had 2nd most snow in history and I did get a little sag on the 2x4's but nothing I couldn't live with.

Per your drawing, you show 3 2x10's. I have the top 2, but I added a bottom 2x6 where your bottom 2x10 is. I removed the metal siding, cut it short, installed the 2x6, then reinstalled the siding.

Next, I used joist hangers, and trimmed the 2x4x16's at an angle, nailed them to the top 2x10 so they were just under the eave. The roof is steel and is under the main eave. no water backs up, and no need to cut into the roof.
Under the joist hanger's, I nailed an extra 2x4 across the length as an extra ledger support.

The rest of the structure is 100% 20' 2x4's. Roof is approximately 16' long, with a 3:12 pitch, 10' at the high side and arond 6 ft. at the low side give or take. they are 24" OC per standard bldg practices in my area. The side walls and every 10' have 4x4 treated posts with the roof joists doubled up in those areas. Roof and endwalls have 2x4's laid flat 24" OC just like a standard polebarn.

I basically used the standard horse shed/leanto plans you see everywhere but attached the high end to my polebarn.

 

[Gibsadal]

Did you ever get this project done. Getting ready to do the same to mine. Would love to see pictures!!

 

[Pathfinders]

Will be following this. My spring project is a 16 x 24 lean to off the back of my detached garage.