What is low rise flashing?
In this video, I wanna show you how to install low rise flashing. Low rise flashing is the edge metal used for torch down roofs. A low rise flashing is a piece of 90 degree bent metal. It has a kick on it. It’s similar to a drip edge. However, it’s called low rise because of this little bump right here. What this allows us to do is it’s an eighth inch high bump that allows us to install the torch down roofing up to it. And then once it’s installed, it pretty much becomes flush to the top of that torch down roofing. This does two things. First of all, it allows us to get a proper bleed out at this edge right here without the hot tar falling over. It also allows us to get a nice solid seam here, a bleed out of hot tar in order to make sure we have a nice, solid seal.
Low rise flashing presents a few different challenges. First off, it is a difference of materials. So we have a metal surface that we’re trying to bond to an asphalt surface. So we have to take a few extra steps to make sure that we have a nice, solid bond. Part of that is going to be installing a layer of smooth rolled roofing underneath it in order for us to sandwich our torch down roof on top of it. So this is essentially what we wanna see. We wanna see a layer of smooth roofing, our low rise flashing, then our torch down on top of it. We’ll get into it and we’ll show you those details that really count.
Installing one layer of smooth self-adhered base
The first step in the process is to install one layer of smooth self-adhered membrane. Again, we’re gonna be using Polyglass’s mid-ply. We found this as a great solution. You can also torch your smooth down. Essentially what we want to do is, just like any other flashing we install, we wanna sandwich it in between a piece of smooth torch down and our cap sheet. So you can see here, this is what we’ll have right here. We’ll have eight inches, six to eight inches past our flashing of the smooth membrane. Then when we install our cap sheet, we’re gonna be sandwiching in between these two layers. Of course, just like any other flashing, we’re gonna be priming our low rise before we start. But before we get into that, let’s install this smooth, then we’ll start prepping our flashing.
What we can do is roll this out while it’s laid down into place. You can just pull that film back off from underneath. If you’re working with a two-man crew, one person’s just pulling this off, the other person is just pressing this down. So one thing we found handy to use are rollers for the self-adhered portion of it. This is pretty much just a four-inch metal roller with a wood end right here. And especially on these ends right here, it’s nice to roll it down. This side of it, where we have our flashing that’s gonna be installed, is not as crucial as this end right here. So we really wanna just focus on this edge. And actually what we’ll do is cut this back right here, as a self-adhered does not adhere very well on the granulated sheet.
How to prime and prep your low-rise flashing
Now we wanna get our flashing prepped and ready to install. Similar to any other flashing, the first thing we wanna do is scuff it up using a wire brush. Now you can use a hand wire brush, but we like to use this. This is a medium to find bristle. And what we’re gonna do is essentially take off this top layer of paint. You’re not gonna completely remove it, you’re just gonna scuff it up.
You can see that this paint is decently scuffed up. The gloss of it is gone, and you have these tiny little grooves across the surface of it. Now we wanna do this on both sides, and I’ll show you why in a bit, but the same concept remains the same for all our flashings. We always wanna do both sides of it. So you can see we’ve scuffed up the back similarly. In some areas you might have that paint removed. Next thing we wanna do is use a vinegar solution. All this is is a regular white vinegar you can find at any local convenient store, grocery store. You can either use this or you can use a metal etching solution. We prefer vinegar over metal etching solution, as it’s cheaper, easier to find, and why not more organic. So you essentially just wet it down. And again, you wanna do both sides. Just for the sake of this demonstration we’re not doing the entire thing. We’re just gonna be doing a small section of it. You can wet it down, rub it down a little bit. And ideally leave it to dry by itself.
We always like to do this at the beginning of our projects, get all our metal flashing prepped, ready to install, so we scuff it, etch it, then prime it, that way during the project we’re not stopping to do one piece at a time. Get all your flashing done, all your prep work done, that way when you’re installing the roof, you have smooth sailing.
Now that the vinegar is dry, we’re ready to prime. We’re gonna be just using really any asphalt primer. This is a quick dry method. It’s gonna help adhesion tremendously, but make sure to prep the metal before priming. You wanna get a good solid coat of primer now on both sides. Something like this is good, good, decent coverage. And again, you wanna make sure you get the backside done too. And I’m gonna show you why here shortly. Once this is all primed and dry, we’re ready to install. For the sake of our demonstration we have a piece ready to go.
How to nail the flashing in place
Alright, we’ve got our low rise flashing primed, prepped, ready to go. We wanna start installing this. We’re gonna be using electro galvanized nails. You always wanna make sure to use the same metal and not use corrosive metals when installing this flashing. So electro galvanized works with aluminum and galvanized. These are inch and a quarter nails. They’re round head. Now you can use hand nails or just for this demonstration purposes, for us to install faster, we’re gonna be using a roofing gun, a coil gun. Now you want to install this with nails every three inches on the center in a staggered pattern. So you can see here, we’ve got three inches here and we wanna do… And so we have three inches here, three inches, and that’s how we’re gonna install the entirety of the…
This may seem again like a lot of nails, but what this is gonna help us do is to minimize the expansion and contraction of this flashing, as metal expands and contracts faster than asphalt does, so you wanna nail it down nice and securely so that expansion and contraction doesn’t cause separation.
How to adhere two joints of flashing that overlap
Now, for this demonstration, what I wanna to do is show you what we would do conventionally at a joint. We could have done this in one piece, but I wanna show you at this overlap what we need to do. This is a very important critical area of the roof, these tend to fail as when the new roofing gets installed, there’s a little gap right here. You can imagine once this is installed, you still have this vulnerable corner right here. What we used to do in these areas was install mastic underneath here, but what we’ve learned recently is mastic is actually counter-intuitive as when it heats up, when using the torch, it actually loses all adhesive components and essentially fails pretty soon, so what we’ve done now is use the back side of this torch down, we melt this tar, and we use this as an adhesive between these two metals. So we found this the best adhesive and really the only solution to use in between these joints. Let me show you how to do that.
What we’ve just done is sandwiched these two pieces of flashing in between the hot tar that you saw was scraped off the back roll of that torch down, essentially creating a seamless piece of flashing. This is really the only effective way we found to make these joints, and it’s a small step, but it ensures the longevity of the roof and a solid seamless finish.
Installing torch down cap sheet over the edge metal
Alright, now that we’ve got our flashing fully installed, what we wanna do is install the top layer of the cap sheet of this roof. The way we wanna do that is first off, roll it out. Now for this demonstration purposes, we cut the roll down to half width. We wanna roll it out and align it. Once we have it properly aligned what we wanna do is roll half of it back, that way, giving us a manageable section to torch with. So now we’ve got half of it rolled back. We can torch this half, then roll this half back and torch that side.
So for this demonstration, what we did was actually install the torch down cap sheet a little too close to the edge. What we wanna do is always have a quarter inch gap between the edge of our roofing and the edge of this low rise flashing; that way we have enough distance there to get a good bleed-out and for tar to fill up that location. So if you do that, what you can do is just cut out a small strip of torch down here, allowing enough space for there.
Torch the seams of the roof perimeter
Another thing that we found as a best practice and the easiest technique for us, a lot of people to do this differently, is burn our seams after we burn the middle and the field of our roof, that way we can really pay close attention and focus on these areas that matter the most. Some people like doing it all in one shot. That’s totally fine. We’ve just found that for us it’s easiest practice and we get the best quality results when doing the field separately and burning the edges separately. So we did the field already. What we wanna do next, and to finish this roof off, is to burn this seam right here and get a nice, solid bleed out along the sides.
You can see here, this is really what we’re looking for, about a quarter inch of bleed-out along the seams, filling up that edge between the low rise flashing and the roof itself, creating a nice seamless roofing project right here.