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Installing Exhaust vents with metal roof
I have bathroom exhaust vents that vent into the attic. I need them to vent to the outside and the quickest way to get them there is through the roof. I have a metal roof though, its a standing seam. What is the proper way to do this once i cut a round hole for the vent? I don't want this to leak. With shingles you trim and put the top shingles OVER the vent base, but i can't do that with a metal roof, so whats the proper way to do it?
The best way to do it is to use a special type of pipe boot m.

This pipe boot is rubber epdm or silicone with a bendable aluminum flange around the base. This allows it to conform to the panel ribs. They come either round or square.

(see the attached drawing)

1. Cut a hole in the panel, just slightly larger than the vent pipe
2. Cut a hole in the top of the pipe boot, slightly smaller than the pipe
3. Put a butyl sealant around the underside of the pipe boot flange.
4. Install the pipe boot, forming the flexible flange to the panel ribs.
5. Put fasteners around the pipe boot, especially beside panel ribs.
6. Put a bead of sealant around the top of the pipe boot where it meets the pipe.

Note: you may be able to use a regular pipeboot by installing it in a different way. You will have to check with the manufacturer of your particular panel to see if this is possible and if so then how.
Sorry I forgot the attachment. Here it is.
Attachments: View Attachment
Nate I hate to be the bearer of bad news but you posted a vent pipe for a plumbing vent pipe. What I think the question is for is a exhuast fan. Typically we vent through the soffit if you cant do that then you can possible seal a metal one directly to the roof.
For bathroom vent fans, we use the same vent that is used for a dryer going through the roof.

Good call. I guess I misread his question. Oops...

I thought he was talking about the exhaust pipe, whereas he was actually talking about a fan vent system.
I have the same situation - a limited storage space above the ceiling (which does not extend to the eaves) so I must vent my bathroom exhaust fan up through my metal roof. Since I do not want to pull up the metal roof, I must cut a hole through it and the vent cap flashing will sit on top of the metal roof instead of underneath shingles. How do I do this so it does not leak? Thanks
FWIW, here is a URL to the photo of the roof. I intend to install the roof vent cap in the section to the right of the section where the plumbing vent is shown. Also, this is the section of roof that gets hit directly with heavy winter winds. The internal construction of the house does not permit me to vent the bathroom fan elsewhere. The debris you see on the roof are pine needles, etc. that were blown onto the roof over the winter. Those will be removed when I'm up there installing the vent.

Corrected URL:

Getting this URL to post correctly is frustrating. One more try:


Looks good. I'll try to post the reply and see if it comes through correctly.
If anyone has the same question, I have been referred to Dektite products. Haven't used it yet but looks like the answer. Re my attempts to enter a url link above, I never could get it to work. I'd carefully type in the url and it would appear incorrectly when actually posted. Who knows what is up with that.
Sorry about that ... not sure either what caused the problems.
Put the penetration in the pan of one panel,
between the seams, as close to the ridge as you can.
Then you cover the entire pan and the seams on either
side all the way up to the ridge flashing. Hem the
bottom edge and close with a zee closer and sealant
Is there a pipe boot that can go over a square bathroom vent as mentioned above?
There are square boots available in some sizes. I have had very good results in the past by using a round boot, applying urethane sealant between the tube and the top of the boot and using a stainless steel clamp to force the top of the rubber boot to conform to the shape of the tube.
Thanks Ken, sorry if these are dumb questions but I am a beginner at this. Am I better off getting the round or square base? The only square base ones I seem to find are the retrofit ones. Would these conform better to the square vent? If I'm understanding you correctly the main trick is to get the rubber to conform to the square vent, correct? When you say tube, are you referring to the square vent itself? When you say stainless steel clamp I am envisioning a round hose clamp with a screw to draw it tight. Is that correct? Would a round clamp work on a square? I hate to ask what seem like dumb questions but I am amazed at the lack of information on the internet about this. It has to be a common issue with DYI metal roof installer. The internet is loaded with pictures and instructions on how to do the round stand pipe but nothing on a square that I could find. If anyone has a photo of how they flashed their square exhaust vent on a through fastener metal roof that would be great. Thanks all.
helped me though thnks
We are having some leaking thru our exhaust fan in the upstairs bathroom. We had the flashing replaced with a rubber one, but someone told us that the pipe is copper and must be replaced with a lead sleeve -- have you ever heard of a stack that is made of copper and not PVC?


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