Flashing a kitchen vent in vinyl siding

Old 01-07-12, 10:07 AM
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Flashing a kitchen vent in vinyl siding

I hit a stopping point in my kitchen remodel: I have the following vent:

HVACQuick - Wall Hoods Galvanized Steel

8" discharge with screen. It's nice because it makes one elbow bend and right into the vent blower.

For some reason I thought finding the right products to trim this out on my siding would be easy, but it has not. I'm familiar with the J-box stuff for putting in an outlet. Those seem pretty easy to install, but I am just not finding anything big enough for that cap. Maybe I'm searching for the wrong thing. The local HVAC shops around here are closed, but I would like to get smart before calling around on Monday (and would love to get this done tomorrow if the box stores carried the right thing).

Any advice on this? I can tell you that it is vinyl siding over sponge board (best term I can come up with for it and no house wrap -- 1978 construction.

Old 01-07-12, 10:30 AM
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I dislike those vents very much because of the way the top angles back to nothing. But if you do use a vent of that type, you have 2 options as I see it.

1). Mount a block of white PVC (like Azek or Versatex) on the house, that has a hole cut in it for your duct. Your vent will then mount on top of the mounting block, and you will be able to j-channel around the edges of the mounting block. To help waterproof the installation, you would (obviously you'd have a piece of vinyl siding removed when you do this) install a large piece of metal flashing around the penetration, and allow it to extend down over the nailing fin of the piece of siding directly below the one you have removed. Then install your mounting block and j-channel as mentioned above. When water leaks in around the j-channel and gets behind the siding it will then be directed out over the nailing flange of the siding and out to the weep holes where it can eventually escape.

2). Get yourself an appropriately sized vinyl siding mounting block (with snap ring) and use this in the same manner as described above, with the exception that you would not need j-channel because the snap ring acts like a j-channel to cover the cut siding edges.

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