How to Install Roof Flashing: Pipes, Penetrations, T-Top

What qualifies as roof flashing?

In this video I’m gonna show you how to install a pipe flashing or any other type of penetration flashing on a shingle roof. Whether we’re installing a pipe flashing, pipe jack or a T-top flashing, or really any other type of flashing on a shingle roof, the concept is the same: the bottom of the flashing is gonna sit on top of the shingle, then we’ll be installing shingles on top of it. Really the only difference is the size of this hole. Whether it’s two inches or eight inches, the flashing method and the steps are the same. So just for this demonstration, we’re gonna use a pipe flashing.

How to prep the flashing for installation

Now the first thing that we’re gonna wanna do and what we like doing is rounding these corners off. This does two things for us: gives us a nicer finish on the roof, as well as takes away these sharp edges. And in my opinion it looks a little nice and cleaner, but those sharp edges may be damaging to the corner of the shingles as this is almost like a razor blade, and these can easily penetrate those shingles. So we wanna cut off those corners.

Paint your flashing before installation

Now before we start the installation, we always wanna paint the flashing. You can do this later. The nice thing about painting it now is you don’t risk over-spraying on your shingles. When painting the flashing, we’re not too concerned about this top because this is gonna be covered by shingles, so we’ll actually prefer not to get paint on here to provide better adhesion. We just wanna make sure we paint this bottom as well as the collar here. We’re gonna give this a few minutes to dry and then start installing it.

How to determine where to install pipe flashing

Now that our flashing is painted, we’re ready to install it. One important thing to keep in mind is the placement of flashing, especially on a pipe flashing, is gonna be determined by wherever your pipe is coming out. Generally being that this is a demo roof, we don’t have a pipe, but on a regular roof we would have a vent pipe coming out. You wanna make sure that the bottom of your flashing at a bare minimum passes this line right here. We don’t wanna install it like this and have our nail heads exposed, nor do we wanna have this nailing strip exposed. We always wanna make sure that it’s past this line. So for example, if our pipe were to finish here, we would have to install one more row of shingles, then our pipe flashing.

You wanna be sure that when you install your next layer of shingles, this joint right here between the second and third layer needs to be past this line right here, past the pipe boot. For example, what you don’t want is for the pipe to be here and a second layer to be here. You can see now we have two layers. That’s what we don’t want. So if that were the case, we would install one more layer of shingles, then install our pipe flashing. For this demonstration, we’re gonna assume that our pipe is coming out from right here and that we’re about three to four inches past this line.

What nailing pattern should you use on pipe flashing?

Since we’re doing a demonstration right here, we’re using a used pipe boot. Generally we always recommend getting new pipe flashings without any penetrations prior.

You can see we’ve installed nails three to four inches apart on the sides. We don’t wanna install any nails down here because this is gonna be an exposed flange, so we always wanna keep our nails up here and not exposed to weather conditions.

How can you provide extra waterproofing around a pipe flashing or penetration?

Being that pipe flashing is one of the most vulnerable areas on the roof, we wanna install a secondary layer of waterproofing. This will ensure that our roof stays leak-free and will expand this flashing out. The ice and water shield is what we install in our valleys, and it’s what we like to do around our penetrations as well. This is not something that’s required, but it’s really a secondary layer of waterproofing that’s just gonna take your roof to the next level. We have this pre-cut right here and we’ll self-adhere this down. This has a self-adhered membrane, so we’ll take off this film. You can see it’s very sticky. And what this is gonna do for us is a few things. First of all, all those nails that we put in here, it covered those nails up. And if you were to get any water here, it would make sure that the water goes down on the shingles and doesn’t get under our shingles. So again, this is a small cost, it’s a small added step, but it really improves the quality of your roof and helps around the penetrations.

How to install shingles around a penetration or flashing

We’ve installed the underlayment, we’ve installed the ice and water shield, now we’re ready to start installing our shingles next to our pipe flashing.

So what we’re doing here is we flip the shingle upside down, and it’s a very easy way to get your measurement. Instead of using your measuring tape, this is a tool that roofers use, is you flip the shingle, now you’ve got your right location here. So one thing around your pipe flashing that you wanna do is leave a quarter inch gap between your pipe flashing and your shingle. What that’s gonna allow for is the water to drain around the pipe flashing as opposed to going underneath the shingle. So we’re just making our mark here and we wanna take it somewhere else to cut, and the reason for that is we don’t wanna damage the shingles underneath. So Marco’s using the floor. And you can see we’ve got our quarter-inch gap right here allowing proper drainage. The shingle on the right side, we’re gonna be installing a full piece as this is a continuation. We started from here, installed a small piece and we’re continuing this way.

Now, you might think we’re missing nails here, this is actually done intentionally. The reason we don’t put nails here is because if we have water coming in here, we don’t wanna have any penetrations right here because this is exactly the flow of water. So what we do is we nail high in these areas, and it’s only on this shingle. Any time we’ve got a pipe boot and we’re cutting around it, we don’t want nails here. That’s a little trick, and it’s very important because you’re definitely gonna get water that’s flowing around here, and we don’t want water to get under the nails.

So now that we’ve installed our second row of shingles, we’re ready for our final piece to finish the pipe flashing off. This piece is gonna be coming over, we wanna make sure it’s aligned, and we’re gonna be cutting this shingle to align with the pipe flashing.

Marco did a great job cutting around this shingle, we got a nice looking cut right here. And again one thing you wanna make sure is you leave that reveal here, quarter to three-eighths of an inch to allow for water flow around here. Again if you imagine water coming down the shingle, when it hits this pipe flashing, it’s gonna wanna move around it. If the shingle’s not snug against it, you risk water going underneath this and going in this area right here, but if you have this gap here, the water’s gonna travel on the path of least resistance. So all that’s left to do is install nails on this shingle right here.

That’s it, it’s as simple as that. Just keep in mind whether you’re installing a pipe boot or something like this, the idea is the same. You want the bottom of your flashing to be on top of your shingles, you want that cut, and always remember that trick. Never install nails right next to your pipe boot because that’s where water flows, leave that reveal, and you’re good to go.

Extend the Lifespan of Your Shingle Roof with Roof Maxx