best way to flash a vent through siding

[EricU]

we have a bottom-vented cookstove. I am redoing the basement walls under it, and it was obvious that there is water intrusion from the vent. I am filling the hole around the vent pipe with foam, but I am curious about how I should flash the hole. It has a rather large enclosure around the flapper. They didn't get the length right, it's about an inch away from the house.. Looking at youtube videos for dryer vents, people just jam them up against the siding and call it good, this doesn't appear to really solve the problem

[Mr_Mike]

Need pictures. Vent needs to be pushed back to the wall. Maybe installed behind siding. Can't flash a round pipe jutting out of a wall, but you can caulk the crap out of it.

Also, what is the construction of the wall?

[EricU]

picture a dryer vent, only super-sized. Ok, I'll post a picture tomorrow.

this vent pipe runs out the rim joist. I am in the process of insulating the rim joists as well as replacing the wall and insulation. The basement is cinder block, and the siding is aluminum. Pretty sure that the siding is sitting on top of tar paper.

[Mr_Mike]

I'm guessing a liberal application of caulk is your only answer.

My kitchen vent is supposed to be installed beneath the stucco and has a flange on 4 sides so it can be properly flashed into place. However, its a retrofit and we don't knock out 2" extra of stucco and have to re-stucco and re-color. Thus, its just caulked into place. Best thing we could do.

[EricU]

Looked at it again, it's actually stuck pretty well up against the siding. I tried to foam the opening, it's not that obvious if I got it all the way around all the way through the rim joist

IMAG0692 by unterhausen, on Flickr
IMAG0693 by unterhausen, on Flickr

IMAG0694 by unterhausen, on Flickr

[DieselDennis]

As I see it you have two options.

Option 1 involves a liberal amount of caulk and hoping that you don't live in the house when you have to replace the siding or the flapper vent.

Option 2 involves cutting the siding to where you have more of a "square" opening and mounting the rear piece of the vent into this "square opening". Then hopefully you could coax the siding back enough to screw the rain cap back on. It would then be up to you to decide if you needed to caulk it or not. Done correctly, it wouldn't need caulking, but I sure don't cut things out that well.

A professional would buy a vinyl siding "block" and give himself either something flat to mount the vent to, or something that he could trim and mate better against the siding.

Google "vinyl siding mounting block" and click on images. Should bring up some good ideas.

[crokett™]

ok that's a bit different situation than I pictured. I would try and find a vinyl siding mounting block that's big enough to cut a hole in for that pipe. the block should be 2 piece. One piece mounts to the wall under the siding. the other is a cover that snaps into place. since your vent has a cover, you may not need the cover to the mounting block. You can cut the block for a much closer fit around the pipe, then caulk that. if possible can you push that pipe back to get the mounting block in? otherwise you might have to remove some siding to get the block in. I installed a mounting block this weekend for a new exterior electrical receptacle. I was able to work the block into the hole but I didn't have that pipe to worry about.

[theeviltwinn]

Cut the siding bigger than the vent. Install J channel to flash around the siding. Install a piece of Azek in the opening. Seal the Azek to the J channel Seal the vent to the Azek.

Twinn

[Mr_Mike]

Sounds like Dave and Dennis have you covered provided you can find the compatible parts. Otherwise, the j-channel method works, but the final product will look more like a picture frame. Both methods are better than you got now.

[crokett™]

can you get the siding of the house easily? If so, the sticky rubber mebrane you might be able to flash around the pipe and the wall and cover the gap around the pipe with it, then put the siding back on.