How to Install Pipe Flashing on a Torch Down Roof

In this video, I wanna show you how to properly install flashing around a pipe or penetration on a torch down roofing system. Let’s get into it.

Intro on Roofing Penetrations

Regardless of what type of roof you’re working on, almost every type of roof has some type of flashings or penetrations that are going on. Whether you have a T-top installed or a pipe where you can install a pipe flashing, these details are pretty much the same. Similar to any drip edge, low rise, scupper flashing, we want to make sure we take a few extra steps to ensure that we have a good bond between our sheet metal and our asphalt surfaces. Let’s get into it and I’ll show you how to properly install penetrations and flashings around them.

Step One: Install Target Patch

Alright, we’re ready to install the pipe flashing. Now, the first thing we wanna do is install our target patch of smooth roofing. Again, we’re gonna be using Polyglass’s self adhered mid-ply, we found this as a great solution. Instead of torching our smooth layers on we’re gonna be using self-adhered. It gives us the same quality, which is faster to install and safer since we’re not using a torch for our mid-ply.

The size of our target smooth is gonna be determined by the size of our flashing. Essentially we want a minimum of four inches around each side. So we’ve got this cut out already. We’re just gonna cut a hole in the center here to fit it in here.

An easy and cool trick to find the center of any square piece is essentially just folding it down, making a crease right here, and folding it down in the opposite direction and making another crease. Not sure if you can see it here, but we have this cross section here, which points out the middle of our patch. That way we can cut a hole and get it installed. This doesn’t necessarily need to be a perfect cut, it doesn’t need to be perfectly tight. As long as it’s about a half an inch or an inch away from the pipe, we’re good. Sometimes if the pipe is a hot pipe, you wanna keep it further away, but generally speaking, half an inch or inch gap is good, doesn’t need to be perfectly tight. There’s two ways of installing this, either we can put it down and remove the film, or if you have two people, you can just remove the entirety of the back film. (Watch the above video at 2:14 to see installation of the target piece.)

Now, what this gives us is a solid piece, so when we install our pipe flashing, it’s gonna allow us to go from edge to edge solid on one piece, instead of going over a joint. Now, before we install the pipe flashing, we wanna make sure we prep it, etch it, and prime it to make sure we have the best adhesion possible. Let’s get going, let me show you how.

How to Prep Pipe Flashing for Installation: Scuff, Etch, Priming

Alright, this is pretty much the same process as any flashing installed on the roof. If you watched our other videos, you’ve seen us do this time and time again, whether it’s for a scupper, edge metal, pipe flashing or T-top, the steps are pretty much the same. Anytime we’re bonding an asphalt-based material to a sheet metal or metal product, we wanna make sure we scuff it up, etch it, prime it, and cut the corners off.

So the first thing we’re gonna do is round these corners. This is a step recommended by our manufacturer. What this does is prevents these sharp corners from puncturing through the roofing membrane throughout the years. Doesn’t need to be perfect or doesn’t need to be uniform. Just take those sharp corners off. The second step in the process is to use a wire bristle brush. We have this installed on our drill. This makes the process faster, easier, and does a thorough project. You can also do this by hand. It’s just a lot faster using the drill attachment. What we wanna do is take this top layer of shine off. We wanna make sure that we get this edge nice and scuffed up. This is really the most important section of roofing to get as this is gonna be our primary area of waterproofing. Now we wanna do the front side as well as the back side here. And I’ll show you why later, but it’s just as important.

After we have our flashing scuffed, what we wanna do is use our vinegar solution. You can use this or a metal etching solution. We prefer vinegar as it’s easier to find and less expensive. You wanna make sure you soak the entire thing, the front as well as the back. And you can just spread it with a towel that’s already saturated with the vinegar and allow this to dry. You wanna put it on one side, let it dry before you prime it. Alright, now that our flashing is dry and etched, we’re ready to prime it. This is just an asphalt primer. Generally, we recommend to use the same manufacturer as you do your torch down roofing. However, all asphalt primers work the same. We wanna give a nice solid coat on both the front side, as well as the back. So you wanna get a good coverage and you want your flashing to look something like this. You wanna prime the back similarly, and I’ll show you why later, but this gives you an additional layer of waterproofing and protection so that you’re not only relying on the front, but you’ve also adhered the back just as properly.

How to Install and Nail Down the Flashing

Alright, now that we’ve got our flashing prime, prepped and ready to go, we can go ahead and start installing it. We’re just gonna slide this on.

We’re gonna be installing it using electro-dip, galvanized nails. These are inch and a quarter long. These have a round head and just for the speed of the process, we’re going to install it using a roofing coil gun. What we wanna do, similar to all our flashings really, is install it in a 3-inch on center, staggered pattern. So, we’ve got our outside edge, nailed every 3 inches on center, then we want to come in about an inch or two and nail again, every 3 inches on center offset from this outer strip. So you have really every inch and a half in a staggered pattern nailed. That’s gonna help a nice tight flashing installation and gonna prevent extensive expansion and contraction making sure that we have a good bond for years to come.

The reason why we primed the bottom side of our flashing is to make sure that we have a bond. Now, you can see that this layer of smooth that we installed has this film on top of it. When this flashing gets heated up, what it’s gonna do is actually melt this membrane underneath it and create a permanent bond between this smooth membrane and this flashing right here.

Cut and Install the Torch Down Cap Sheet

All right, now that we’ve got our flashing installed, we can go ahead and line up our torch down to start installing it. We’ve already cut a smaller hole right here. Pretty much once you roll it out, you wanna cut a relatively similar sized hole on the membrane itself. However, you wanna make sure that the hole that you cut is smaller than the actual opening. Once it goes over, now you can use this as a template to cut around it. So, now we’re gonna cut around it. You wanna leave an eighth to quarter inch gap between the membrane and the flashing itself. So this gap that you see here is really not a problem, and it’s actually preferred to have a little bit of space, and similar to any other area in torch, when we burn this area, we wanna have a proper bleed-out to fill this gap up with that hot tar. (Watch the above video at 7:56 to see how we use a torch to install the torch down cap sheet.)

Final step: Polyflash 1C Coating

The last thing we wanna do to wrap this pipe flashing up is put a coat of PolyFlash 1C. Now we wanna put that both around the pipe-to-flashing joint as well as this membrane to flashing joint as well. Even though this is completely sealed and waterproof right now, we have a nice puddle of melted tar here, we wanna put a second layer of PolyFlash 1C on there just to protect it a step further. Now you don’t necessarily have to use this PolyFlash 1C, you can use any white mastic or Silicon caulking. However, we prefer the PolyFlash 1C as it works great with the system. You don’t have to go too heavy on here. Really just wanna cover that gap up. That’s it. This pipe is gonna be waterproof and stay nice and tight for years to come.