In this video, I wanna show you how to install
torch down roofing around a cast iron drain on a flat roof.
Let's get into it.
A cast iron drain is probably one of the most difficult details
on a torch down roof.
The primary difficulty about it is you have such a small flange around here,
and unfortunately that's how these old cast iron drains are made,
that you only have an inch or two to properly overlap your roofing.
The second difficulty about it is that cast iron is a thick piece of metal which does
not get hot when you're welding, so getting a good seam between that cast iron and your
torch down is extremely difficult.
Now, we've come up with a few different techniques that we like to use with our manufacturer
rep, and these techniques really provide a solid, seamless, good waterproofing system
for our drain, so we wanna show you all those little details.
And similar to scuppers, you can watch our video on that, cast iron drains have a lot
of water flowing to one area, so even if you have a small pinhole leak, then you can have
a large problem, you can have a huge leak because you have
a large volume of water draining to one area.
So pay special attention to your drains, to those areas on the roof that you have a lot
of water draining to, and make sure you do things right.
Let's get into it.
The first thing we wanna do before we get started is make sure we're flush between
our cast iron drain and our roofing material.
Sometimes there's an offset, sometimes it's sank in, sometimes it's raised up.
This demo that we've built actually has a higher lip, so what we don't wanna do is,
we don't wanna lip this down and create a ponding area right here.
So we just wanna put some sacrificial pieces right here, lifting this up
so that when we install our final piece of torch,
we have positive drainage into the actual cast iron drain.
So this part is not too difficult.
We're gonna be using a self-adhered membrane,
and this actually plays a big part in our roofing process.
You can use this or smooth roofing material torch down.
We found that it's safer to use self-adhered on the midply, so in your mid layers, instead
of using a torch, you minimize any risk and any danger by using a self-adhered system,
and it's not as critical of an area since it's not the top layer,
so we use self-adhered midply, then a torch cap sheet.
So what we wanna do is without removing the film,
and this is just to raise up this area around the drain,
roughly center it, and we're gonna push down on these bolts
just to pop them out.
This is not perfectly square, but it's totally fine,
and we're just gonna feel out these corners and start cutting them.
So, one thing I actually wanna point out is before we started the video,
we actually already installed one layer right here,
and you can see the idea is
we want to taper them down,
we don't wanna have all two layers or three layers starting in the same location.
We wanna have one larger piece right here, and then come down to a smaller piece,
and we're gonna put a last piece smaller so that we're tapering it down,
we're stepping down so that we'll have a smoother transition.
Now, the nice thing about this material,
it has this film that gets melted off when we're torching our top player,
so that we have a real nice seam when we go down.
So we're gonna do one more just to get a smoother transition.
All right, now we are nice and level here.
So you can see if we install a piece on top, we're gonna have a smoother transition.
We have three layers that we actually installed around this, just to build this area up,
which gives us a smooth transition.
Anytime we're torching or using an asphalt-based material
on top of a metal -- cast iron, sheet metal, or anything like that,
prime it with an asphalt-based primer.
What this does is it ensures a better adhesion between the metal and any asphalt,
whether it's self-adhered or torched down.
There's really not much science behind this, you just want to give it a nice solid coat,
make sure you have full coverage on the entirety of the metal,
and you only have to prime the area that you'll be torching.
So this is a quick-dry material, within a few minutes,
it will be tacky enough, ready to start installing our material down.
So when we do our drains, we actually wanna install a target piece.
What that means is we're not necessarily doing
the roofing here along with the rest of the roof.
What we like to do and what the manufacturer recommends is installing a target piece,
a three foot by three foot area of roofing, finishing it off,
then bringing the new roofing, the rolled roofing, on top of this area.
That way when the water drains, it'll drain on top of that target piece that we have,
and our drain does not have any seams in it
because being the most vulnerable area on the roof,
you don't wanna have a seam right down the middle, you wanna make sure that
you have one piece of roofing all around.
And the only way to ensure that is to install a target piece.
So we've got this cut out already.
These rolls are 36 inches wide, actually 33,
and we're doing a rough square around it,
and we're gonna start off by roughly aligning this and poking through.
Now that we have it centered, we just lift up half of it.
most of these self-adhered membranes have a slit down the middle,
so the easiest way to do it is removing half
and leaving half on there just so you don't lose your centering.
Just want to press that down firmly.
You can use a roller or just your hand in a smaller area, it's totally fine.
And do the same thing on the other side.
All right, now that we have this done, we're ready to start cutting.
We wanna start off by cutting a circular hole,
substantially smaller than the actual opening itself.
If this is the opening, we wanna leave two to three inches here
in order for us to be able to start cutting and bending the material down.
So, regardless of the size of your bowl, you wanna find your outer edge.
And it's always better to leave more than less, because you can always shorten it later.
But we wanna cut it down to about an inch to an inch and a quarter.
We call these finger cuts.
And what this allows us to do is actually bend the membrane inside.
And we wanna have a minimum of one inch past this inner lip right here.
And we'll show you how to do that later.
We're gonna be bending this down and clamping this down.
And just make sure that you're leaving this long enough.
So depending on the size of your drain, it will determine the size of this hole right
here and the length of these pieces over here.
You just wanna make sure that the back here is anywhere between an inch to three quarters
or inch and a quarter, something like that.
And we're gonna be cutting this all the way around.
So once these are all cut, we wanna lightly form them with our hands
and start pressing these down.
You can see how we're going into the drain.
And this side should have actually been primed too.
So we didn't get enough primer on here as we should have.
But anywhere that you're installing a self-adhere or torch, again if we're going on metal,
just remember to prime all these areas.
So what we wanna do right now is actually install our ring clamp,
and this is gonna be a temporary installation.
And the reason for it is it actually helps us mold this base layer
and form it down to this groove right here.
Having a good bond between our membrane and cast iron is near impossible.
So we really wanna rely on this mechanical fastening system, clamping it down, creating
essentially a little channel here that doesn't allow the water to come back up.
We actually wanna fasten this evenly on all three sides, similar to like a tire.
Once you get the drain clamped down nice and tight,
you wanna wait generally about 5 to 10 minutes, especially on a hotter day.
It'll form nice and fast.
You can use this time to get any of the other tasks done on the roof
and prep to install the final target patch.
But you just wanna leave this on here.
It's gonna help it form and give you a nice tight seal.
Now that we've waited a few minutes for our clamp to kinda tighten down that self-adhered
mid ply, we're gonna remove it and start installing our last piece of torch.
You can see that has given us a nice tight crease right here, created a nice tight seal
and when we install the last layer of torch,
we're gonna have the same thing done even better.
So we already have our target patch cut out,
and similar to the mid ply, we wanna align this.
We wanna have this roughly three feet by three feet or three feet by 30 inches is fine.
Remember, we're gonna bring our field membrane on top of this, and we wanna make sure we
have about a six inch gap between our drain edge right here
and the field membrane that comes on top.
So you can do a little bit bigger, a little bit smaller.
You're totally fine.
So what we wanna do is we wanna align it, center it,
and start poking the same bolts through.
And now that we have this done, we're gonna start torching.
The way we are gonna start torching is lifting up half, similarly, torching this half down.
We are not yet going to cut the center hole or do our finger cuts.
We're gonna burn and adhere the sides, then start working on the middle.
Just like any time we're working on torch, keep safety in mind.
Make sure you have a fire extinguisher close by.
You wanna have it anywhere from 5 to 10 feet away from you
so you can quickly access it if needed.
Now that we've got the rest of the field of this target patch
torched down and installed already, what we're gonna do is
we're gonna do the same thing that we did on our mid ply.
We're gonna cut a small circle out from the middle,
leaving about two inches from the edge of this drain.
That's gonna allow us to cut those fingers out and bend them in.
And ideally we wanna get those opposite or kind of staggered from our mid ply
so that we're kind of interlocking those.
And we'll see how that works right now.
Again, the size of this hole is really gonna be determined by the opening of your drain.
So a larger drain is gonna require a larger hole,
whereas the smaller drain will require a smaller cut.
So once we have this cut out, we're gonna start by cutting the three angles at the bolts,
then start cutting those at again about an inch to inch and a quarter widths,
which is gonna allow us to fold these down.
Alright, now that we've got our hole cut out and our finger joints cut as well,
we're ready to start actually torching these down and adhering these one by one.
Again, we wanna stagger these as much as possible
so that when you're cutting, you wanna make sure that they're offset.
So if your mid-ply is this, you wanna make sure your cap sheet is this
so that you have good coverage.
One thing that we like to use in these small areas is a plumber's torch.
This really helps in making an easy and controllable flame
for us to work in these tight and confined areas
instead of using a big open flame.
This is a lot easier, safer, and allows to do controlled work.
So we're gonna start slowly one by one, torching these down.
Alright, now, that we've got all these individual tabs torched down,
what we wanna do is, we're getting close to the end,
is just clamp this down again while it's still hot.
It's important to do this while it's still hot in order to be able to get
a nice form on these, and really mold that into the cast iron shape.
This is something that we actually used to not do right away.
We used to do this at the end of the job,
but we recently learned the importance of doing this right away.
So that while the membrane is still hot, we're able to get a nice form on this.
Again, you wanna make sure to tighten these evenly without tightening one side too much.
Once you have this tight, you wanna have it sit for at least 5-10 minutes, if not more.
Really just let it sit for as long as you can until the membrane cools.
That way, it'll really hold that form and keep that shape after it's done cooling off.
The last step or second to the last step is removing this ring
and putting a coat of sealant all around it.
We've already waited 5-10 minutes, let it cool down.
Remove it and get ready to finish this off.
Any time you are on a roof, make sure you don't lose these bolts
because they're going to be difficult to find later.
So what we're gonna be doing is applying a coat of PolyFlash 1C.
Now, we like to use this because we are using the Polyglass system,
and this is a sealer of choice for us.
You can use any other type of white mastic.
However, this is what we prefer, and really recommend.
We've had great success with it.
The way we like to apply it is using either two or three inch.
Just one of these cheaper brushes from Home Depot
or your local hardware store will work.
You wanna put a solid coat, but be careful from over-applying it.
You definitely don't wanna put it on too thick.
And make sure you don't get it on these bolts themselves.
You also wanna make sure that you are applying it here on the inside,
on each one of these notches and grooves.
Now that we've applied the final coat of PolyFlash 1C around this drain,
we wanna wait for that to fully dry and cure before we install our ring clamp on
and call it a day.
Now that we've got our sealant applied, it's nice and dry, we're ready to install the clamp.
Similarly to the rest of the times we've installed it, we wanna make sure that the drain clamp
is installed evenly, that all three bolts are tightened uniformly.
You wanna get nice tight pressure on there, as this drain clamp is gonna help keep that
membrane nice and tight and stuck to the roof.
So you do wanna make sure it's tight.
Install this drainer cap.
And we're good to go.
This drain is gonna be nice and waterproof for years to come.
Guys, thanks for watching.
We have a lot of other videos on this channel about torch down roofing.
If there's anything that you like to do different, let us know below.
We'd love to hear from you.
Give us a like, subscribe, and we'll see you in the next one.