Q&A / 

Roof Flashing for Bathroom Fans Video

First, if you are not comfortable working on the roof, do not attempt this project. Falls resulting in injuries or death are possible.

From inside the attic, locate the hole where the vent will go through the roof. It must be located between two roof joists. Once located, drive a large nail up through the roof from the attic.

Once back on the roof, you can locate the center of the hole from the nail. There should not be any chimneys, other vents or other objects within two feet of the center of the hole.

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Mark the hole on the shingles with any marker you can see on the roof shingles. Make the hole slightly larger then the diameter of the vent tube.

Use a reciprocating saw to make the cut in the roof. You can cut right through the shingles at the same time you are cutting the roof sheathing.

Shingles are overlapped so the rain will run off the roof. The upper shingle is always on top of the lower one with part of the lower shingle underneath the one above it.

The flashing on the bathroom fan vent works like a shingle. If it just laid on the roof, the flashing with be above all the shingles and the roof will leak. The top edge of the flashing has to go under some shingles.

To do this, some nails have to be removed from the shingles. The nails should be located directly above the slit in the shingle. Lift the shingle and located the nail. Use the flashing to determine which shingles are affected.

Use a flat pry bar to remove the nail(s). If the part of the vent is not round, some of the shingles will have to be cut to match the vent. Put the flashing in the hole and outline the flashing edges.

Cut the shingles so they are about 1/2" inside the edge of the flashing markings. A razor knife can be used to cut the shingles.

Once cut, slide the upper part of the bathroom fan vent flashing under the shingles at the top. The vent flashing will sit on top of the shingles on the down roof side. Nail the roof flashing in position.

Apply caulk over any nail head that is not under a shingle. This will keep that nail hole from leaking.

Done properly, your roof vent will not leak.

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13 Responses to Roof Flashing for Bathroom Fans Video

  1. Thanks for the video, I changed from old soffit vent to a roof cap vent while upgrading bath fan. Had new roof put on 3 yrs ago and was nervous about making a new hole in it, video was helpful to keep me from over thinking it. Also saved me money by keeping me from dumping 20 lbs of sealant around the area to get a warm and fuzzy about no leaks like I would have in the past.

  2. We had a contractor install a vent through the roof for our bathroom. It has leaked every since when it is windy and raining very hard. The contractor insists it is our roof not his installation of the vent. It NEVER leaked before this. He insists this without coming out to look at it.
    Any thoughts?

    • Paula,

      You want my thoughts? You've got a LOSER contractor. He, or his roofer, is a rookie. Did you watch the video? I'm sure if I had YOU up on the roof with a few tools, YOU could install the flashing so it wouldn't leak. This is roofing 101. Threaten him with BAD REVIEWS on all the social platforms and online contractor referral networks.

      • HaHa...Thanks...I have been thinking the very same thing. If he does not fix it to my satisfaction, meaning FREE, then I am going to tell Angie's list and the BBB all about it. I was VERY happy with all the other work they did for me. Including the installation of ANOTHER vent in our other bathroom, which does not leak. Our bathroom remodel looks awesome, but this leak is very annoying and like you said, I probably could fix it myself if I could get up on the roof, which I will not do on a two story house.

  3. I installed a roof vent like the one in the video (boy, I wish I'd seen your video before I did it) but here in the Boston area, it's caused problems. The issue is that when I've got a foot or more of snow on the roof, the vent sends hot air over the roof, melting the snow, and ultimately causing ice dams on that area of the roof.

    I noticed that some other vents are just pipes that go straight up a few feet, but I haven't been able to find anything that looked like the right size to change this.

    What parts do you use for vents on snowy roofs?

      • THANK YOU for replying.

        Your videos show exactly what's happening, but it only happens where the bathroom vents warms and melts the snow so it flows down and makes the dam.

        Elsewhere, the insulation prevents the snow melt and the dams. I'm pretty happy that I keep snow on my roof longer than my neighbors—proof of my insulation. When we put in the insulation, we left an air gap between the insulation and the roof, so the air flow flow from the soffit keeps the roof cold.. Except where the bathroom vent blows warm air directly onto it.

        Is there a bathroom vent duct that extends 3 or 4 feet above the roof? I see them for the plumbing, but not for the vent.

  4. Hi,
    We're in South Florida & have a metal roof. Currently we don't have any ventilation fan in our bathroom (1947 house) & would like to install one, preferably an in-line type. I am very leery of cutting a hole in the metal roof (and not sure the vent would meet hurricane code) You are opposed to venting through the soffits, but in this case, do you have any other suggestions?

    Thank you for your expertise.

    • If your house has a gable end, exhaust it out the gable. You can install a leak-free flashing in metal roofing. Contact the manufacturer of your metal roof and they should have a step-by-step guide. I've done it countless times. You need a pro installer and the manufacturer may know the BEST one in your area.

  5. Hi, do you have any videos or links to installing a weathertight vent on a corrugated iron roof? Tiles aren't so common here. Thanks

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