Gable End Lean-to Plan---Critique?

[jaw22w]

Only the structure of my new 30x40x12 pole barn is up, and I am already planning a lean-to expansion. The lean-to will attach to the 30' gable end. I don't want to mess with the corners of the new building so the LT will be inset a foot from each corner. 28'x12'. The pole spacing is 10' on the end walls of the barn, so, I bought (3) 2x12x10's and had the Amish crew install them directly below the end truss at 12' as a girt directly under the siding to be used as a header beam for the LT. My thought is to use rafter hangers screwed into this 2x12 through the siding @4' centers for the 8 rafters. Rafters will be 2x8x14 with the 12' span to provide a 2' overhang. Support will be (4) 4x6 posts @ 9'-4" O.C. with 2x10's inside and out of the 4x6's.
Flashing the LT to the building I think will be the worst part. The plan at the moment is to cut the building siding at the proper elevation after the roof sheets are on the LT. The bottom chord of the building end truss will be the vertical backing for the flashing. Then remove the sheeting above the cut and install an angle flashing down over the LT sheets. I think that foam closure strips are available to close the gap between the ribs and the flashing. I know they are available for the inside of sheets.
Does this sound like a plan? Any suggestions?

 

[jack stand]

Plan (sketch/draw) this out carefully. Typically construction would have a 2x and the 1" overall thickness or "profile" of the panel not to mention the plane of the pitch against the vertical wall above the rafters.
I would cut the wall metal before framing if you have an overhand on the gables.
A few pictures would have been helpful.

 

[sjvicker]

I agree, pictures and sketches would be very helpful here.

I can't see a reason why cutting the wall metal last would be a good idea. It makes more sense to me that you'd want to cut out and expose your full header beam and build off of that then flash under your wall metal and over your roof.

 

[Brly]

As above, I would cut your steel back first, expose the header and make your rafter connections directly to the header instead of over the steel. Get the lean to up and roof on. The angled flashing piece will slip up behind the steel on the building and run out on top of your lean to roof. You should be able to do this without removing any panels on the gable. I used the foam sealing pieces on the underside of the angle flashing to seal against the lean to roof.
This is the best photo I have from when I did mine.

 

[Hooked]

What type metal are you using? Is it coming from a company like Mueller, etc? If so, they can most likely bend sheets of the siding for flashing so no foam pieces required for sealing. At least Whirlwind here in Houston has done similar for me in the past.

 

[jaw22w]

You guys are right it is hard to follow a verbal description rather than a drawing or pics.
Sorry about the sideways pics. I tried 3 times to get them rotated correctly and gave up.
I think my design will work, but this is my first pole barn and my first try at pole barn type design.
My thought on making the cut after the sheet metal is on the LT roof is it may take a while to get the rafters and roof deck on this thing as I will be working by myself except for weekends, and I do not want the inside of my soon to be insulated walls to get wet. It is only a 3/12 slope on the barn, so with the LT starting at 12' there is not much siding above the LT roof deck. Pretty sure I can make a slice slightly above the LT roof line, remove the upper sheets, install flashing, and reinstall the upper sheets in a day.
I'm not sure why installing the rafter hangers onto the sheet metal and into the 2x12 behind would be a problem as long as the hangers are installed tightly?





Anyway, this should make my plan a little more clear. Anybody got any heartburn with this plan?
Thanks

 

[trashyman]

Your plan will work imo till one of the rafter hangers layout falls on one of the ribs. Aren't the ribs every 9"? Cutting metal last is not difficult but sliding the flashing up last could be a bear.

 

[CombatNinja]

Dumb question, but is that building brand new? Why was it not just built with the lean to from the outset?

 

[jaw22w]

Your plan will work imo till one of the rafter hangers layout falls on one of the ribs. Aren't the ribs every 9"? Cutting metal last is not difficult but sliding the flashing up last could be a bear.

Yes, the ribs are every 9", But that 4' o.c. is not written in stone. I'm figuring that if I had to move one or two rafters a few inches, the 2x4 purlins would never know the difference. I will have to make sure that the two end rafters do not land on a rib.

Dumb question, but is that building brand new? Why was it not just built with the lean to from the outset?

Well, I'm 72 years old and did not want to take on the 30x40x12. I think I still have a lean- to left in me and can do it a lot cheaper than paying someone to do it. I'm figuring right at $2K in materials to finish out the lean to. I have always built my own stuff. My house, my shop, my son's house and shop, my hotrods, etc, etc,. It just about killed me to hire the building out. Just facing the reality that I can't do everything I used to could.

 

[jaw22w]

Cutting metal last is not difficult but sliding the flashing up last could be a bear.

There are 10-3' wide sheets on that end of the building. The 8 middle sheets will be cut clear off and will be removed for flashing installation, then re-installed. The end sheets will only be cut about 2/3 of the way. They will remain and I can swing the loose end out of the way to install the flashing. But yeah, I thought about it, and I don't think it could be done without removing those middle 8 sheets. The longest sheet to be removed is only 3' long.

 

[bb29510]

after you put the rafter up. run some 1x4 acros the rafters pertticler, a row about every three feet to hold your tin

1x4 are cheap