How to Install Torch Down Cap Sheet

Explanation & Prep

In this video, we’re gonna be installing a roll of Polyglass torch down roofing. What I always recommend is make sure that you install the entire system properly.  So not only the torch down cap, but your base layers, your flashings, follow the manufacturer recommendations. We like working with Polyglass and we use their base layer, their mid-ply, as well as their torch cap sheet. Anytime that you are torching, please make sure to work safely, have a fire extinguisher close by. In the field of the torch down, it’s important to properly burn the back of the roll to get good adhesion, as well as getting a nice bleed-out of all your seams. Let’s get into it.

Setting up to torch the first roll on your field

Alright, we’re ready to get the field installed. So in this video, I wanna show you essentially how to install just a simple roll of roofing. We’re not gonna be doing penetrations or any details, flashings or things like that. Just how to install the middle of the roof, what we call the field of the roof. The way we install it is a two-step method. We first burn the middle of the roll, then we go back and do the seams. You can do it both ways. However, we found that we get the best results for our seams if we do it in a two-step method, that way we can really focus on the seams and getting a nice bleed-out, as the middle of the roof is really not as critical as the seams.

The first thing we do is we lay out our roll of roofing. Now, for this example, I don’t wanna go all the way because I do wanna show you how it is to terminate and start a new roll of roofing ’cause on the field on regular-sized roofs, you’re gonna have that quite a bit. You’re not gonna have your rolls go all the way from one side of the roof to the other. So we’re gonna assume that the roll ends here and then we’re gonna continue another lap here.

Side laps: explanation and purpose

Torch down rolls have a side lap, which is this right here. These rolls have 3 inches along the length of the roll that’s made to burn and adhere one to the other. This really allows us to get a good, solid joint when we’re burning here. Now keep in mind, this roof is made for a demo so generally we wouldn’t have areas like this. You don’t wanna have this exposed to the sun. Really in this video, we’re showing you two things: install the field of the roof, and how to do your joints. So we just wanna make sure that the edges are aligned, start rolling it back, then we’re gonna start torching.

Start installing the torch down cap sheet

Now, one thing that we’d like to do a little bit differently than how some other people do it and how some manufacturers suggest is, we like to burn and kick the roll out in front of us, as opposed to standing on the backside and using a J hook to pull that back. The reason is for safety purposes. We never like to walk backwards on a roof. You always wanna walk forward and see what’s ahead of you because it’s very easy to step off the edge if you’re not looking. So we’ll actually stand on the field itself on the roll, burn it and kick it out.

When we’re burning it, we wanna get this film burnt and melted. Now we’re staying back 6 inches from each side as these seams we’re gonna do separately. And really, you wanna have the majority of the flame here and 30% of the flame on the base itself.

When you’re installing your field, if you ever see this top become brown from heating up the bottom side, that means you’ve overheated it and you don’t want to do that. You can burn through the membrane and also if you heat it up too much, you can permanently damage it, which will cause premature failure.

How to dog-ear the corners of the cap sheet

So we’ve burned our field down and the next thing we wanna do is start burning the seam. Now before we do that, these ends right here, what we wanna do is cut it at a 45-degree angle. And what that’s gonna allow us to do is, when we have the new roll that’s coming on top of it, it’s gonna allow for a good bond right here. If we were not to cut this off, we would have a double layered system right here which would essentially allow water to possibly seep in through here. By cutting this at a 45-degree angle will allow us to get a good bond right here at this vulnerable corner.

Now, as this is heated up, he’s pushing it down with the trowel and he is achieving that quarter to half-inch of bleed-out that we’re looking for. So this is a perfect looking seam right here.

How to torch a new roll at the joint of the previous roll

So we’ve got this first area done. As I mentioned, we cut this short to simulate an end lap. So end lap occurs when you have one roll ending and another roll starting. You wanna have 6 inches of overlap
between the new roll and the old roll. Keep in mind, this corner here should always be cut at a 45-degree angle, and what that’s gonna allow us to do is this new roll will bond to this base and still have a 3-inch overlap. So this is about 3 inches right here and our new roll is gonna extend about 3 inches past this.

Now at this end lap here, we have some special precautions that we have to take because the field is not prepped, these side laps have this overlap area where it has a film that burns off, the end laps do not have that. So in order to prep this for a proper bonding, we’re gonna heat this up to remove the granules, then adhere the new roll onto the existing. The way we wanna do it is, lay this over and using our trowel here we’re gonna make a light mark across the entire thing. That way we have a light indentation. You don’t wanna go too deep. You don’t wanna cut into the material, but you have that guide for us.

Now we’re able to heat it up and embed the granules. So you can see, what we did here was embed all those granules into the asphalt. That way, when we flop this over, we’re not burning this new material onto granules, which is not gonna bond as well as it is right now. Right now, when we have all those granules gone, we’re gonna have a real smooth and tight clean finish.

You can see what Ronal was doing before, he was using his trowel as a guide not to overheat this area of the roof, as opposed to just keeping the heat on the left side where we wanna get rid of those granules. So, now we’re ready to flop this over, burn this, and get a nice tight seal on both the end lap and the side lap here.

Alright, now we have our end lap done. You can see we’ve got a quarter-inch bleed-out all the way across, which is exactly what we’re looking for. We have our last side lap to do here.

How to install granules over seams

I’m gonna show you one last detail that’s really, in our opinion, an optional detail, and that’s to granulate the seams. You can buy these at any roofing supply. They’re essentially the same granules that
are on top of your roofing membrane. In talking to our roofing manufacturer and our manufacturer representative, this is really an aesthetic option as opposed to a water-proofing requirement. So, really, if you wanna make your roof look seamless, you can install these. The nice thing about letting the bleed outs stay, is that you can see the bleed out, and the proper bleed out that you’re supposed to have.

So, I’m gonna show you how to apply this. Really, as someone’s doing the seams, one person needs to go behind them and spread the granules out. It’s not rocket science, you just throw them on there, and they’ll stick on top of that hot asphalt.

So, we have an excess of granules here. That’s always gonna happen when you’re granulating your seams. Once this roof is cooled down and the asphalt has hardened, you can brush away or blow off the excess granules.

So, as you can see, this is what a granulated seam looks like, and this is what an un-granulated seam looks like. And it really, in our opinion, talking to all our manufacture reps, both of them will perform the same, it’s just a matter of aesthetics. You can see which one you like better.

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