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This still doesn’t explain why overlapping rooflines are actually problematic, though. I have always wondered this myself, as I actually own a house with a det

This still doesn’t explain why overlapping rooflines are actually problematic, though. I have always wondered this myself, as I actually own a house with a detached garage where the previous owner and next door neighbor put an easement on file that allowed the next door neighbor (whose ground level is about 5 feet higher via a retaining wall) to build an outbuilding very close to the property line with the roofline hanging over my garage by about 6 inches. So far, the only practical downside is that my downspout ends up getting all the water from half of his roof, which means the problem is worse if I don’t keep it clear. Not a terribly big problem in my book, since I have to keep it clear anyway. What else am I missing? (Note: there are other things that are suboptimal about my garage, namely that it was built 100 years ago right on the property line and when it was rebuilt sometime later, it was allowed to stay there despite normally having a 5 foot setback requirement. As a result, this concrete block structure itself actually serves as part of the retaining wall and has moisture seepage issues from the uphill side. I actually think having the neighbor’s outbuilding covering that patch of land and managing the rainwater via my downspout helps the matter, because the ground between them gets no rainfall at all.)

hinkley 5y ago
It’s a “this is why we can’t have nice things” situation. There’s no physics problem with overlapping that I know of, but it’s a giant loophole for people who are up to no good. It’s not so much that you shouldn’t be able to do it as that there’s no way we can do it without a permit.
- throwaway9870 5y ago
  No physics problem? I consider a fully equipment fireman carrying a person trying to squeeze between the house and the shed to be a physics problem. And yes, those situations are considered when codes are written.
  - hinkley 5y ago
    Very true. The best I could come up with was humidity control, but ingress/egress issues make fire marshals demonstrably cranky.
- hamburglar 5y ago
  So you think my garage is fine? Seeking anonymous expert-sounding internet validation :D
  - ethbr0 5y ago
    The thing to remember about building codes is that they're one solution to a problem. More often than not, one good solution. That isn't to say they're the only solution. So for new construction or reno, absolutely follow code! Why not? But for old construction that doesn't have obvious dangers and has served its purpose across decades? Why fix what ain't broke? It's entirely possibly it's a perfectly viable alternative solution.
- horsawlarway 5y ago
  The water management issue is a bigger deal in some locations. In the original post, he's sloped the new roof back towards the house - huge issue where I live (Atlanta - we got a lot of heavy rain) since that's going to cause water entry in the basement or erosion on the foundation. It can also be a fire hazard in many situations. Ex - in my area there's a mandated 10ft gap between the property line and any structure. It's there to prevent people from building right up to the property line, essentially creating townhomes, but with none of the fire/safety planning those require. All that said - I agree with you, this code is likely there to discourage people trying to skirt around inspections (and because it's easy to spot).
  - ethbr0 5y ago
    Rainfall treatment around foundations is the most bizarre "new city" difference. Previously lived on clay soil above the freeze line: everything needed substantial gutters and routing away from home. Now live in sandy soil below the freeze line: most people don't even have gutters.
- deleted 5y ago
  [deleted]
alistairSH 5y ago
In this case, the shed will have rain runoff into the house. Possibly not a problem, but generally not a good idea. Also, as mentioned, sheds don’t usually need inspected. Sheds with power that act as extensions to the home should be (should = good idea) but might not be required, depending on location. Basically, some of these rules are to prevent uninspected/unpermitted extensions to the main dwelling.
- hinkley 5y ago
  I've heard it said that frugal home improvement is a very good reason to stay on very friendly terms with an electrician. You can frame and wire a new room in the basement, but not attach it to the mains, then have them come out and tell you if you did it right before anyone dies or burns the house down. You pay them for a couple hours instead of the whole project. You could try chatting up your electrician on a simpler house call, or you might be able to chum around on a Habitat for Humanity project and get a hook-up. Most people try to avoid electrical wiring or plumbing repairs (other than faucets), because the blast radius is so high. The bravest I've gotten is rewiring a light fixture, and I went extra slow to make sure I didn't end up flying off the ladder. I taped a cup over the light switches so nobody could help, and it still felt like when you're trying to fish something out of the garbage disposal and keeping one eye on the switch to make sure nobody even looks at it.
jcrawfordor 5y ago
Fire safety is a major motivation throughout the building code, and this rule is kind of a proxy to fire risk assessment. If you join rooflines then fire can jump from one to the other. Larger structures and structures used for residence are high risks for fatalities if a fire spreads too quickly and/or without adequate ability to evacuate. Structures assembled ad-hoc over time tend to be high fire risks for several reasons, and avoiding permitting and inspection requirements avoids any check on that.

hinkley 5y ago

It’s a “this is why we can’t have nice things” situation. There’s no physics problem with overlapping that I know of, but it’s a giant loophole for people who are up to no good. It’s not so much that you shouldn’t be able to do it as that there’s no way we can do it without a permit.

throwaway9870 5y ago
No physics problem? I consider a fully equipment fireman carrying a person trying to squeeze between the house and the shed to be a physics problem. And yes, those situations are considered when codes are written.
- hinkley 5y ago
  Very true. The best I could come up with was humidity control, but ingress/egress issues make fire marshals demonstrably cranky.
hamburglar 5y ago
So you think my garage is fine? Seeking anonymous expert-sounding internet validation :D
- ethbr0 5y ago
  The thing to remember about building codes is that they're one solution to a problem. More often than not, one good solution. That isn't to say they're the only solution. So for new construction or reno, absolutely follow code! Why not? But for old construction that doesn't have obvious dangers and has served its purpose across decades? Why fix what ain't broke? It's entirely possibly it's a perfectly viable alternative solution.
horsawlarway 5y ago
The water management issue is a bigger deal in some locations. In the original post, he's sloped the new roof back towards the house - huge issue where I live (Atlanta - we got a lot of heavy rain) since that's going to cause water entry in the basement or erosion on the foundation. It can also be a fire hazard in many situations. Ex - in my area there's a mandated 10ft gap between the property line and any structure. It's there to prevent people from building right up to the property line, essentially creating townhomes, but with none of the fire/safety planning those require. All that said - I agree with you, this code is likely there to discourage people trying to skirt around inspections (and because it's easy to spot).
- ethbr0 5y ago
  Rainfall treatment around foundations is the most bizarre "new city" difference. Previously lived on clay soil above the freeze line: everything needed substantial gutters and routing away from home. Now live in sandy soil below the freeze line: most people don't even have gutters.
deleted 5y ago
[deleted]

alistairSH 5y ago

In this case, the shed will have rain runoff into the house. Possibly not a problem, but generally not a good idea. Also, as mentioned, sheds don’t usually need inspected. Sheds with power that act as extensions to the home should be (should = good idea) but might not be required, depending on location. Basically, some of these rules are to prevent uninspected/unpermitted extensions to the main dwelling.

hinkley 5y ago
I've heard it said that frugal home improvement is a very good reason to stay on very friendly terms with an electrician. You can frame and wire a new room in the basement, but not attach it to the mains, then have them come out and tell you if you did it right before anyone dies or burns the house down. You pay them for a couple hours instead of the whole project. You could try chatting up your electrician on a simpler house call, or you might be able to chum around on a Habitat for Humanity project and get a hook-up. Most people try to avoid electrical wiring or plumbing repairs (other than faucets), because the blast radius is so high. The bravest I've gotten is rewiring a light fixture, and I went extra slow to make sure I didn't end up flying off the ladder. I taped a cup over the light switches so nobody could help, and it still felt like when you're trying to fish something out of the garbage disposal and keeping one eye on the switch to make sure nobody even looks at it.

jcrawfordor 5y ago

Fire safety is a major motivation throughout the building code, and this rule is kind of a proxy to fire risk assessment. If you join rooflines then fire can jump from one to the other. Larger structures and structures used for residence are high risks for fatalities if a fire spreads too quickly and/or without adequate ability to evacuate. Structures assembled ad-hoc over time tend to be high fire risks for several reasons, and avoiding permitting and inspection requirements avoids any check on that.