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I've recently started smelling a musty smell in my upstairs bedroom. The bedroom closet just happens to be where the downspout from the main roof drains onto the roof for my garage and creates a kind of corner in the roof. As I have been looking into it, how the downspout has been configured feels completely wrong.

Is there any way this makes sense? Why angle to downspout into/up the slope of the shingles as opposed to out and across the slope/away from the siding?

downspout angle downspout angle 2

philmonroe
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    Once you have or even before you have that downspout directed away from there, check to make sure that corner is sealed tight or have the sealing redone. That corner might hold onto water and cause leaks into the house. – crip659 Mar 19 '23 at 21:49
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    I’ve got the company that installed the gutters and redid the roof coming this week for a warranty repair. I plan on having them reassess the flashing and siding as well. The wood siding definitely needs to be replaced as I t falls apart just by touching it with my finger. – philmonroe Mar 19 '23 at 23:45
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    @philmonroe I'd be getting them to remove the shingles, check and repair if necessary, the probably rotten substrate, as well. – SiHa Mar 20 '23 at 07:21
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    Why install like that? Most likely because that was the last elbow they had on the truck and it was easier to put that on there than it was to go to back to the shop to pick up the right part. – FreeMan Mar 20 '23 at 15:59
  • The intention MAY have been to stop a large flow overtopping the lower edge. If so, a solid sheet on top of the shingles would have stopped water being driven up and under them. – Russell McMahon Mar 21 '23 at 12:44
  • @FreeMan An alternative explanation: it's for cosmetic reasons, since this way it's not visible from the front of the house (is the impression I'm getting). But I still think it's completely wrong. – Героям слава Mar 21 '23 at 13:41
  • Please see: [answer to: "How to prevent heavy rainwater from jumping the gutter?"](https://diy.stackexchange.com/a/71591/27397) for an explanation of what's best when routing a downspout from one level down to the next with a picture of an implementation – Makyen Mar 22 '23 at 03:23

3 Answers3

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It's completely wrong!

The shingles overlap each other. This ensures that water running from top down doesn't enter under them.

When you flush water against the overlapping sections, they are not water proof. Water may enter under the top shingle.

You should ensure that water flows from shingle on top to shingle under it.

vidarlo
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Get it out of that corner and have the water flow downwards not upwards under the shingles guaranteed to leak.

You just need one more part.

Downspout Side Elbow

elbow

Loves

Ruskes
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    There are [Type A and Type B](https://www.gutterworks.com/tips-and-resources/a-vs-b-styles) elbows, and this has the wrong one. But even with the correct type, you'll still need at least one more elbow and an extender section to ensure that the outflow is directed downward and not across the shingles. (Across isn't as bad as upward, as it is now, but it's still wrong.) It that's hard to set up, you might consider a [Flexible Downspout Extension](https://www.lowes.ca/product/downspout-components/amerimax-flex-a-spout-255-in-downspout-extension-20111). – Ray Butterworth Mar 20 '23 at 02:42
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    I might argue that the OP needs *two* elbows—a B elbow attached to the downspout, and an A elbow attached to the B elbow, to turn the water more downslope than across slope. – Huesmann Mar 20 '23 at 12:18
  • OP already has the A elbow - I think this answer implies it's to be re-used below the added B elbow, but it could make that clearer. – Toby Speight Mar 23 '23 at 16:35
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That down spout is the termination point for ALL the rain water on that side of the roof! All that water is being directed to a small area and shot against the overlap of the shingles.

Do yourself a favor and remove all the gutters and downspouts on the second floor. Let the roof shed the rain as it was designed to do and let the lower roof collect the rain. You then don't have all that water concentrated in one small area.

RMDman
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    To clarify: there are other downspouts from the primary/second story roof as well. Some go to the other side of the lower garage roof, while others go all the way to the ground. I would estimate that this downspout gets 1/8 to 1/6 of the rain off the primary roof. It’s still quite a bit of water though… – philmonroe Mar 20 '23 at 01:05