Bought a house a few months ago where the roof of a one-story garage meets the wall of a two-story house, like in this image.

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Recently noticed that there is mold and a leak in the corner of the garage. Only leaks when it rains reasonably "hard". Directly above it is the roof. First home, and really just now getting into the DIY of it, but upon examining the roof (image below), I'm fairly confident the water is seeping in between the siding and roof of the garage. There doesn't appear to be any flashing, which would explain the water leak.

enter image description here

Would I be able to install flashing on over the shingles, and under the siding, like in this last picture? Assuming I can get under them once I take the 2x6 off, of course. Or, am I going to have to remove the shingles, put flashing down, and replace the shingles?

enter image description here

  • I've inserted flashing similar to your last picture and it seemed to work pretty well.
    – Hot Licks
    Commented Oct 2, 2022 at 2:47

2 Answers 2


Adding or replacing the "step shingles" (the flashings you refer to) might help but without taking off some roof shingles it is not at all a guaranteed fix. Those step shingle flashings are normally installed as you are laying the roofing and are meant to be inserted further up the roof than you will be able to get them. The fasteners that hold down the roofing (nails or staples) will be in the way of you sliding them up enough to be installed as they are intended.

Adding these step shingles without taking up some roofing along the edges may help, but as long as you are going to the trouble of removing the 2x6 I suggest removing some roofing along the edge and weaving the step shingles in properly.


Assuming that the top part of existing metal flashing that is in the picture goes under the siding, You can go ahead and install edge flashing.

Test run the first edge flashing by feeding it under that flat metal flashing and just lay it down over the roof. This gives you an idea what you are looking at. What you are envisioning is that the flashing will be going under the second layer of roofing and over the first layer. And the next one over the second layer and under the third, over the third layer and under the 4th .... and on and all the way to the top.

If the flashing looks like it didn't go far enough under the roof overlap due to nail being there, just cut the flashing so it won't hit the nail and will enable you to feed the flashing further up so it lays the right amount over the first layer.

Also you won't need to use any patch either. The roof has sufficient slope And the water won't be going anywhere except right down the roof and over the edge.

And there you have it.

Take good care.

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