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Discussion Starter · #1 ·
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Sometime in the past a contractor installed this flashing between the siding and the concrete stoop. He sealed it with tar and then concreted over, which, of course, failed and has been leaking water under the flashing. The stoop gets a lot of water coming off a valley just above the brick column where I am going to install either diverters or capless gutters and is exposed to the elements, getting rain and south Mississippi morning sun. I’ve removed the concrete he used to cover the flashing and fixed all the water damage from the inside. The flashing goes between the subwall (tongue & groove heart pine) and the outside siding so the outside siding wasn't damaged, just the subwall.

Any ideas on the best way to seal the flashing to the concrete, especially considering it is exposed? No problems in caulking the top part of the flashing where it meets the siding, but not sure what to use to seal the flashing to the concrete. I’ve thought about using some type of urethane adhesive and then covering with something like a strip of EPDM single adhesive roofing repair/joint tape (but I don't know whether that would bond to concrete or how it would look). I don’t think flashing tape is a good choice because of the exposure. Whatever I come up with, what would be the best way to prepare the concrete for a good bond?
I have been hesitant in removing any of the siding because if I damage it I will have to have it remilled since it is not a standard profile. I am willing to remove it someone knows of a better way to flash this.

I know this is a bad design and the best solution would be to tear out the stoop but that is not an option at this time.
 

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Discussion Starter · #3 ·
Yes. Got no responses here but did get responses over at roofing.com. I ended up removing the siding, tar paper and flashing and replaced all the rotten wood. You probaby won't have to deal with this but I had to grind down a lot of concrete on the stoop at the back next to the wall to level it for new flashing. Someone had poured a crap load of concrete in the opening and on the stoop over the flashing trying to seal it sometime in the past. Anyway, new wood, tar paper, and I reflashed with a piece of vinyl coated trim coil, about 5" on the stoop and 7-8" up against the wall.

What made this work was using a water stop butyl rubber caulking to seal the flashing to the concrete. There are various butyl rubber water stops out there but I used the Firestone S-20, made for this purpose. It is made to be used with compression. I ran a couple/few beads of the caulking on the concrete first and then placed the flashing over it and rolled it with pressure. It rolled flat and I didn't have to secure with any concrete fasteners. And there won't be any water getting under there. It is pretty sticky and nasty to work with, so make sure you have mineral spirits handy and rags. If you want you can practice with a concrete block and a small piece of flashing to see what it's like to work with.

I chose trim coil over the standard zinc plated flashing because it's a little thicker and will roll out better without kinking or rippling. Hope this helps.
 
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