Is adding a large lean-to roof for a large shed going to exceed the limits for the IBC definition of a shed? The shed (details below) is already at the IBC limits for shed area and height.

The lean-to would be along the long edge of the shed and be approximately 33.5 x 12 feet, no higher than 9.5', with a pitch of 2/12 to 3/12. Posts would support it on the low side.

The shed has a footprint of 28.5 x 14' (399sf). The eave height is 9.5' (IBC definition of shed as I understand it), The shed also has 3' overhangs on all sizes and a dual slope roof (7/12 and 10/3) that results in a total height of about 20'. The projection of the roof is currently 33.5 x 20.

  • What's a 10/3 slope?
    – isherwood
    Commented Jan 16, 2017 at 17:37
  • You're going to have to contact your local building department, they're the only ones that can answer this question.
    – Tester101
    Commented Jan 16, 2017 at 19:25
  • @isherwood That would be a 40/12 slope, I think?
    – Tester101
    Commented Jan 16, 2017 at 19:27
  • That's my guess, but why the weird notation? Also, that's church-steeple steep.
    – isherwood
    Commented Jan 16, 2017 at 19:30
  • 10" rise over 3" run? Yeek Commented Jan 16, 2017 at 23:04

1 Answer 1


If (as I infer) you are in an area where an "IBC Shed" is not requiring a permit, and larger things are, you either need to separate the new space (so you have two "sheds" that are not actually connected) or you need to pull a permit; unless your area restricts you to one "shed" and then you're simply going to have to pull a permit.

If memory serves, the IBC definition is based on "projected roof area" of the "shed" - so two conjoined maximum-sized "sheds" are no longer a "shed."

  • When I requested the permit, our inspector only cared about the footprint, not the roof projection - so its still a shed in our town. Any chance you could find the roof projection statement in the 'IBC'? I guess once I bring support posts down to the ground, I grow the footprint....
    – pathfinder
    Commented Jan 17, 2017 at 16:41
  • I did not bother to look it up, I'm simply going on what I recalled; could be wrong. As always, the LAHJ interprets as they like. And yes, if the posts hit the ground the footprint gets bigger.
    – Ecnerwal
    Commented Jan 17, 2017 at 16:49

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