Roof Flashing for Bathroom Fans 

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An exceptional video. One tip I have is when you are in the attic driving the nail guide through the roof, lay some plastic down on top of your insulation to catch debris from the hole cutting. This easy step makes cleanup a cinch.

Thanks for the comment. I disagree with you however. If what you say is true, then tell me why the entire roof of my house doesn't leak when I have driving rain and melting snow? Regular shingles do NOT have a fat bead of caulk under the edge or at any point under the shingles. Simple gravity prevents water from backing up. Now, in the case of ice dams that BLOCK this downward movement, you can have leaks. Watch all my Ice Dam videos to see how to prevent those leaks.

I went through a couple of videos, some of which recommended removing entire roof shingles. Your video was clear and simple, and it took me no time to install two vents (one plumbing vent and one bathroom vent). Thank you for this, you are awesome!

And you shall see *many* more in-depth videos. Rest assured of that. :-> Thanks for your kind words. It means very much coming from a peer who knows the challenges of doing work in all sorts of different situations.

I just installed a Broan 634M (my first roof vent install), and so far no leaks! This video was the best of the bunch, but I was confused by the stark difference between it and the instructions that came with the Broan (they recommend tons of nails and caulk). I ended up using three metal sheeter screws along the bottom edge, since that's what I found on all the vents already installed on my roof, but I did not use any nails under the shingles. I did use caulk; I added a vertical strip on the underside of the shingles that lay on the flange, and I also added a thick bead along the top and both sides of the vent, per the Broan instructions. I was surprised to find many layers of shingles, and wasn't quite sure how many to cut through. I ended up cutting through all of them (~3) along the top edge, as this allowed me to have three of the four courses of shingles on top of the flange (this video shows 2 on top, but all my existing had 3, so I went that way). MY ONE BIG MISTAKE was that I did all my marking, and thus cutting, based on the vent sitting in the hole. The problem is that gravity pulls the vent to the lowest point of the hole, which results in your vent being pinched along the bottom edge. Unfortunately, I didn't think about this, or notice it, until I went inside and looked from the attic, at which point the vent was already screwed down and caulked. It wouldn't be such a problem if it weren't for the Broan having a VERY short collar to attach to. I'm actually going to have to careful drill and chisel out some of the wood to make my connection. It's something I never thought about, and is a lesson learned for me.

Technically not a day-to-day roofer. But I've installed more than I care to remember, and have done all the flashings, soldering, tinned box gutters, etc. I always found it fascinating to see how roofing worked to make a house watertight. That interest is what tends to make a person good at something. You then treat it as a vocation instead of a job.

looks clean. my only concern would be the metal flange is,pretty small. I would put roofing yards or caulking around the metal under the shingle to prevent leaks. especially on a 3 tab roof. an one more corse on top of the flange below the last course that is on top of the flange. other that that good install. ..

@blanknot go back to 1:54 and start watching that section again. It's all about overlap. The metal flashing is providing plenty of overlap on the lower shingles and is being overlapped plenty by the shingles above it.

I'm pretty certain in this video I did have a pilot hole. But it's been so long since I taped it, I forgot! To cut without one, hold the recip saw at a low angle to the surface. The blade might be at a 15-degree angle. Turn on the saw and slowly pivot the saw up at a steeper angle as the blade chews into the wood. Do this slowly until the blade penetrates the wood.

With regards to caulk....In 1972 (Yes long ago) I was trying to figure out why a vent on an attached rear porch was leaking--once in a while. The interior ceiling was a finished 12" acoustical tile typical for the day. I knew it had to be the roof turtle vent above the leak which had no obvious fault apparent. Learned the leak was rain driven from the east, into the side of the vent, where the narrow piece of shingle sat. The water was being driven into and escaping beyond the hidden flashing edge becoming the leak. After Blackjacking the shingle to the flashing (Underside of the shingle), it never leaked again for the remaining 5 years I lived there.

@bladder1010 You're most welcome. You can return the favor by telling as many people as you know about them and all the columns at my AsktheBuilder website.

@d1incharge Thanks for your comment, but I respectfully disagree. The piping of the moist air must be continuous to the exterior. You can't *hope* the air all makes it out a nearby pot vent. And with a high-quality fan, you don't hear the flapper. And as for leaks, are you serious? Installed the way I show and you'll never have a leak. That vent has withstood fierce wind-drivin rain countless times.

excellent video Tim. When it comes time to getting your roof replaced be sure to replace all your vents and flashing. I like to suggest purchasing higher quality ones so they will last and you won't have any problems with leaks down the road.

Nice video,straight to the point with no fluff!! Thank you!!

Thanks for your comment. This flashing doesn't leak. It's been in for several years through driving rain and deep snow. I went to your channel and there's nothing there. If you are an expert roofer, how about sharing your knowledge with videos? Show us your methods. The method for installing the flashing in slate or wood shakes is the same. If you disagree, then tape your own video showing us how you do it.

And I really apreciate all these helpful videos. You know, it just doesn't add up sometimes, does it? I watch your videos, I learn a lot from them, I enjoy your helpful advice, insights, and sense of humor, too. I think "Thank God for this video - just in time to help me get that job done". Meanwhile, I read the comments - often ugly! Yikes! What are those guys thinking? Thanks again, Tim, - your work is much appreciated!

Thank you for showing and explaining it so simply for those of us who are not roofers!

@d1incharge I built in the Midwest for over 20 years. :->>>> You want to find the best roofer in your area? I can do it in less than two hours. For you to do it, all you need is my Roofing Checklist. Go to my AsktheBuilder website and click the SHOP button. You'll see the Checklists. Each contains four secret videos that show you exactly what I would do if I was in *your* town and had to find the BEST contractor for any job. Guaranteed to work. Try one and see.

Thanks! What many people forget about flashings is they work just like field shingles. Think how regular shingles have no black jack under them. It is solely gravity keeping you dry. Remember too that nearly 42 percent of every average shingle is exposed. So leaving that much flashing exposed is no different than a shingle. :-)

1) Instead of nailing the bottom part and using caulk to seal them, "steel roof" screws could be used. These screws come with a rubber washer and will never leak. 2) I would also put a small patch (size of a quarter) of tar over the top nails to seal them and also to hold the shingles in case of high wind.

Indeed they are. Rock is not too bendable, unless it is heated to about 1,500 F and under maybe 50 atmospheres of pressure.

You are most welcome. More videos are in the works.

It may not be necessary, but would it do any harm by sealing with caulk just to go the extra measure and doing the best install job possible? Caulk is fairly cheap and it can aid in keeping the flashing tight to the roof in addition to the nails to provide extra hold down power. Houses with problem trees like pine trees, the caulk can help keep any debri buildup to a minimum in the event flashing lifts a bit. Also I feel caulking under shingles is a good way to ensure they stick to the new vent

thanks for the video, this will be a great help, cause the guys who, did ours, definitely didn't know what they were doing or just didn't care,. thanks a lot..

@chunge12 You call in a professional. Use my Roofing Checklist at my AsktheBuilder website to help you DISCOVER the professional in your area.

You are most welcome. Comments like yours offset the ugly ones I get from time to time....Sigh! I appreciate the time you took to comment.

good point always tuck vent flashing under shingles , as well as silicone chaulk it all. I like the nail trick for locating it, would work on pretty much any type of fan or any thing you want to mark for cutting

@d1incharge Ahhhhh! We get to the root of the problem. Glad we had this discussion. So, I'll ask you, *what* is the problem? That's a rhetorical question as I know what the issue is. The problem is a vent that allows snow to enter the house. Are there snow-proof pot, soffit, ridge vents? Well, there are some that claim to be so. Now you need a manufacturer to prove to you that they really have a vent that will not allow snow to enter. Thanks for your respectful discussion.

Same way, but you need a flashing that conforms to the tile. Sheet lead can be used.

I can. I thought that video was already uploaded. If not, it will be within two weeks.

Do you have a roof flashing question? Don't want a LEAK? I can call you on the phone: shop.askthebuilder.com/products/15-Minute-Phone-Conversation-with-Tim.html

@AsktheBuilder lol. Please keep these videos coming, I love all of them

@dekonfrost7 Well, I've got news for you. The flashing is just like a shingle. You have part of a shingle exposed each course, right? That's why you can do it my way with only 20 -30 percent of the flashing exposed and they'll NEVER be a leak. You need to pay attention to how things really are built.

When I did this in NJ with a Braun vent, I use a tri polymeric roofing caulk. I applied it on the underside of the vent on the top and sides. NOT on the bottom. I also applier around the hole on the wood decking to keep the wood dry. Every nail gets a dab on the head. The existing shingle tabs get a dab on the black dots. and Press the shingle with something flat into the caulk. Dont leave a raised shingle. Not he only cuts the top shingle.

Bryce Puntenney You may be able to get the flashing at a big box store. Usually the exhaust fan manufacturers make - or offer - the vent hood. The one in this video came with the FanTech fan you saw in the attic at the beginning of the video.

Same exact procedure, but you need to use a flashing made out of lead that bends to the shape of the tile.

Soffits are bad juju. The moist air can roll under the soffit and re-enter the attic through soffit vents. You can seal the shingles to the flashing with a roofing cement if you like. No need for it if you do it the way I show. Mine have never leaked, and I've installed hundreds of them.

@nickolas233 Glad you enjoyed it. Pretty soon I'm taking off RU-vid. Others will have to pay to watch it. This giving content away for free is not working.

Thanks for the helpful videos! I have to do this exact thing to my house tomorrow morning, so I really appreciate the info! Thanks, Tim!

Is sealant only needed over the nail heads? I would think it wouldn't hurt to put some under the vent flashing where it lays over the shingles on the bottom half to prevent wind driven rain from being driven uphill to the vent hole. FYI - I do home improvements but never roof penetrations so this is a legitimate question that I'd appreciate feedback on.

Yet another wonderful and very helpful video. Thanks, Tim! One question--it looks like you know how to cut through the roof with a reciprocating saw without first drilling a starter hole. What's the trick? I can't do it without the starter hole. Again, thanks for ALL your highly informative videos--I've learned so much from you!

Thanks for posting the video. It was clear, complete and well executed. I'm replacing bathroom fans and the vents (currently soffit). This will definitely help. I found in the comments how you started the recip saw cut without a hole; I'll try that at ground level first.

Great instructional video. Thank you AsktheBuilder :-)

You need to go to a commercial building that has upper stories that look down on lower roofs. You'll see all sorts of vents popping up through flat roofs. Bottom line: Of course you can install it on a low-slope roof. In that case, I'd incorporate the ice and water membranes that flash it to the felt paper so that wind-blown rain can't enter under the shingles.

I don't comment on code issues. They are different in all areas, and even when using the UCC, the local inspectors can override sections. You ask your local inspectors.

How much time? More than 25 or 30 years? I have many vent flashings like that installed on my roof, and they have been there since day one. No leaks. I suggest that you consider there is more than one right way to do something. Keep in mind that regular shingles in the field do not leak, and each tab is not sealed as you suggest.

Probably. Check with the fan manufacturer for approved roof caps.

You can if you want, but it's not necessary. Using that line of thought, you'd caulk under every shingle. You'd caulk under every piece of step flashing. I've *never* caulked under any flashing like this - even on a low-slope 4:12 roof. I've NEVER had a leak with no caulking. But you can do what you want..... I can't see your roof from where I live. :->>>>>

This guy is awesome I wish I had half the skill he does

Not dumb at all. The answer is usually. One would hope there is an attic access panel or even a door and steps to the attic. Not all houses have this as some ceiling joist are also the roof joists.

Technically speaking there is more than gravity keeping those overlapping layers sealed together ”Both 3-tab asphalt shingles and laminated asphalt shingles contain a strip of factory applied adhesive that is activated by the sun's heat after installation and seals each shingle to the next course. The seal strip also provides much of a shingle's resistance to wind uplift. Shingles with factory-applied adhesive have a strip of clear polyester film applied to each shingle to prevent the sealing strips from bonding the shingles together when packaged. When the shingles are installed, the self-sealing strips will not align with the plastic film strips and will bond to adjacent shingles. For this reason, the plastic film strips do not have to be removed.” www.nrca.net/roofing/Asphalt-shingles-899

Thanks this vid is very helpfull.I need to install a roof flashing for my bathroom exhaust also.

You'll do great. Just don't miss a step.

Thank you very much, Tim! I tried it today and it worked great--appreciate the tip!

Excellent and right to the point video... well done!

Same technique. Make the slit in the metal roof half way up the flashing. The slit in the roof is exactly the same width as the flashing.

You can caulk over the exposed nail heads. Look how much of each shingle is exposed - five inches.

thanks for all these great videos, can you upload drain tile installation. You know those plastic pipes with holes in it.

Thanks this was very helpful. The instructions on theses roof vent kits seem to be written by Chinese and very confusing. This video really helped. Thank you.

Man this is a great video. Very well-explained in a short time.

No sealant. It's tough to do on a remodel like this without taking out the shingles completely. I have three of these identical flashings on the roof and no leaks in the worst wind-driven rains. The pitch is 9:12. If it was a new roof, I would not hesitate to use sealant as an additional safeguard.

Pretty good! I would use clear silicone though instead of regular caulk.

Wow -- you're a great teacher. Thanks for your clear presentation!

@d1incharge I'm stunned. The only risk you have with a penetration if you use a *loser* roofer. I've cut *thousands* of penetrations in my career. Never has there been a leak. Did you take high school Physics? Hot air does what? It rises. It doesn't go down. You put a vent pipe from a fan near or next to a pot vent and the hot air will *rise*. Some or all of the air will float past the vent and coat the roof sheathing. All you have to go is go up in an attic on a cold day and test your theory

Thank you very well done

just a lil tip you should put the next row of shingles over the vent as well... stop any leaks... time over time i have had to repair leaky vents done this why..

Hey this is great, I need to install one of these, the moron that I had install the bathroom fan just has the hose pointing towards the soffits, now I see dark spots on the wood!! Now I just need to grow the cojones to go up there and cut a 6" hole in my roof!! Thanks and I'll be coming here for more instruction!!

great video! nice job... but what type of vent cover on the roof should I use for an 8" 900 cfm kitchen exhaust ?

I used Tim's method and my roof has not leaked for well over a year now. You should go on that know it all show on Discovery channel.

In this installation, the shingles sit on the top 1/2 of the flashing. Is there any reason you cannot have the shingles sit under the top 2/3rd or have the flashing completely underneath? I ask because I have a very shallow pitched roof, a dormer that is pitched maybe 10 degrees. I think there could be a little more sideways movement of water than on a normally pitched roof.

Do we need to use any sealant underneath vent? Or do shingles do the job of keeping water out?

Great informative video! Is this installation any different with concrete tile roofs?

Great video and detailed explanation! Thanks!

Informative. Thanks! Any experience w. metal roofs? We need to replace a duct vent that vents straight up from 1st floor dryer up through 3rd floor utility closet to metal (sloped) roof. Somewhere along the length, its become disconnected and does not vent properly. We'd like to use existing roof vent cap. Is it pretty straighfwd to remove vent so we can pull out old duct and slide in new one? Concerned about keeping metal roof integrity as it was just scraped and resealed this summer. thanx!

hey builder guy, i hope you covered the top of the exhaust fan before you cut the hole in the roof.

I did as you said and I 'did' see a picture showing what appears to be the same setup you had, but nowhere could I find the brand name of the roof vent you installed. I'm also still wondering, if both bathroom fans already have exhaust fans, if a remote fan in the attic is really necessary.

Always like your videos. Two things I like to ask, Those nails driven right through the shingles? That seems kind of odd to me. A potential leak in the future with rusting out? And so much flashing exposed? Shouldn't the shingles cover more of the sides?

but is it easy enough to take cap off and then replace? we don't have to cut a new hole as there is already one there. thanks much. p.s. we are doing this today, so hope to see a response! :)

Awesome video, thanks. I guess once the hole is cut you're committed! LOL

The row underneath the flange should also be over top the flange like the top shingle, if you do it like that you should definitely run a bead of sealant on the exposed edge of both sides of the flange..

Nope, this video was taped in the heart of the Midwest in Cincinnati, OH. I'm always sort of amused when fellow RU-vidrs suggest to me what video to tape next. The thought that crosses my mind is, " ... well, heck, they have a RU-vid channel of their own, why don't they tape the video? After all, it's a community." So your video can start out with a wide shot of the old folks clambering up their ladders and crawling across their roofs. Then get into the meat of the topic.

I have two bathrooms that are basically next to each other. One has an exhaust, the other does not. When installing the new exhaust fan, can I just "T" into the existing vent that is vented outside of the house or will I need to have two seperate vents??

I would have put that third row over the metal . any time you have a full exposure of a row it is to go on top of the flange wether it be a b- vent, air vent, plumbing stack, sky light,chimney(step flashing)think about driving rain blowing in the side were your hole is cut. then you could nail the side of the flashing down and have your shingle cover the nail. In B.C. where we see lots of rain.ive had to fix afew flashings that were installed that way. 23 yrs in this trade.

dekonfrost7 I hate to disagree and agree at the same time as I thought you were right but I looked at my GAF spec book (2006) and on page 112 it shows the installation for a SSB960 slant back Master Flow vent installed as he did it. He did face nail and caulk the heads which NOBODY does which should be done, but he did it by a manufactures book.

great video, can i use that type of vent for an under the cabinet hood vent?

No sealant or tar underneath the bent’s flashing? Is that because this is 13 years ago or is it unnecessary? Which would I use, asphalt roof. There are so many options

you are lucky you have such pliable shingles! I have slate shingles on my house, a real PITA to work with.

Why did you not use roofing caulk to seal the upper and side flange?

@AsktheBuilder I take it you are in a colder coastal climate? Ever seen the "roof vent covers" for sale at Home Depot? You should make a video about the risks of using those. We surely both agree roof vent covers to "hold in the heat" are not only going to void your OSB warranties, but will do more harm than good. Every year I see my old retired neighbors crawling up their roofs to put those on, yikes.

@pashastookie Thanks. I wear a superhero costume under that blue shirt. :->>>>

Just wondered if you know of a remote exhaust fan that has a built-in humidity sensor?

Would you full install this vent and then run your round duct up to meet it? Could I use a roof tar (tube) for added protection before laying down the vent on the shingles?

Realize this is an older video. It’s good, but really should have addressed how and where to seal the shingles to the flashing to prevent leaks. I think that is the most important step of the job.

Great Video. I'm going to be installing a vent during the spring. My dad wants to vent it through the soffits because hes worried about the roof leaking. Since I'm installing it, I find it easier and more efficient to go through the roof. Is there any advantage/disadvantage venting through the soffits? Should if I do vent it through the roof should I apply some tar to seal between the top of the vent and the shingles?

Will the design of this addition reduce , preferably greatly reduce noise of flapping exhauset vents to inside bathrooms ? It’s maddening! We live on a hill and catch so much wind

I answer questions like that using my phone consult service.

No need for that product. Watch the video again. I used no caulk or roofing cement as part of the flashing process. I *did* put a small dab of caulk on the visible nail heads on the exposed base of the flashing. Nails in that location keep the flashing from blowing/bending up in vicious windstorms.

we don't have a kind of roof like that, in my country!!! but nice video

Only under the top layer!