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Flashing at concrete deck

Chris_River's picture

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I have a question about how the flashing/waterproofing should be done between the rim joist and the concrete deck that will be poured. The deck will be 12 feet wide, poured in a pan, and rests on a full height block wall on the outside and the 4" brickledge on the house side. There are two bays on the house, but other than that it's just a straight run. Since there will be a narrow (3') roof it seems that this will be the most likely place for rot to begin. I'd like to know if anyone has either good or bad experiences in how they protected this area, and what kind of seal/caulk to use (knowing that caulk is 'temporary' in the long haul). There will be vinyl siding in that area for the time being, but will be replaced with brick sometime in the future.
My thanks to anyone who can give me any tips or suggestions!

(post #171926, reply #2 of 5)

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I flashed on a concrete deck once, was arrested. It was a deck attached to a bar in downtown San Antonio. Did two days in the city pokey.

(post #171926, reply #3 of 5)

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Thanks for the advice. Actually the fellow is putting a piece of aluminum (flashing, I presume) down against the band joist, and it is fine if it continutes down under the deck because it's not a finished floor under there. I figured caulking the joint between the aluminum and the concrete, and then flashing on top of the deck to direct water away from the house. For the time being there will be siding in that area. I've heard so many conflicting things about caulks, I appreciate the comment about using urethane.

(post #171926, reply #5 of 5)

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I have a question about how the flashing/waterproofing should be done between the rim joist and the concrete deck that will be poured. The deck will be 12 feet wide, poured in a pan, and rests on a full height block wall on the outside and the 4" brickledge on the house side. There are two bays on the house, but other than that it's just a straight run. Since there will be a narrow (3') roof it seems that this will be the most likely place for rot to begin. I'd like to know if anyone has either good or bad experiences in how they protected this area, and what kind of seal/caulk to use (knowing that caulk is 'temporary' in the long haul). There will be vinyl siding in that area for the time being, but will be replaced with brick sometime in the future.
My thanks to anyone who can give me any tips or suggestions!

(post #171926, reply #1 of 5)

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Do not pour against the band. Do not pour against a pc of alum. kick that goes down below the slab but does not deal with water dispersal. You'll have to figure the detail to be both appealing till you get it bricked up and useful in getting the water away from the joint.

When you get to it, Urethane caulk is in my opinion the only way to go for sealing mas. to mas., metal to mas. or anything to anything for that matter. It's not easy to use but will tool nice with a wet finger. Surfaces must be clean and dry for a good seal. Cleans up with thinner. Read the directions and cautions. Best of luck.

(post #171926, reply #4 of 5)

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I'm pretty sure the alkaline concrete will corrode the aluminum, especially if it's mill finish. I think you can assume water will get in there, even if the joint is sheltered, because of flooding, debris, wind-driven rain, etc, so drainage should be provided. Technically the concrete/wood interface is an "expansion joint" where you'd expect movement. It's a joint that's going to be damp much of the time.

I have a concrete stair against my band joist, and yes it led to rot, and I haven't yet come up with a solution I like except perhaps flashing from under the siding, down then over the stairs, ending in a caulked groove in the stair ... like chimneys are done, but in reverse.

PL makes a good polyurethane masonry/metal/wood caulk (in white, gray, and black -- I suspect they are all the same thing in different colors). Vulkem makes a similar masonry caulk some like, but the smell I find REALLY nauseating! Mineral spirits are good for tooling too. The stuff will stick to anything clean, especially you! The "big stretch" caulk looks worth considering too, very tough and stretchable.