Roof Torch Down
We began weatherproofing the roof this week, despite a continued beatdown from Mother Nature. The sky has been perpetually grey and in between the snow and rain, we’ve been rolling out and torching down a SBS modified bitumen membrane (I know you want to say that 5 times fast).
We’re using a product called TorchFlex, which is described as:
A strong reinforcing mat (polyester or fiberglass) which is coated with SBS modified bitumen. Styrene-Butadiene-Styrene (SBS) is a rubber-based chemical that endows the asphalt with some amazing qualities: superior elasticity, excellent moisture resistance, and exceptional cold weather flexibility. The end result is a long-lasting, durable membrane which can be applied to a wide variety of surfaces on roofs of almost any shape or design.
Installation seems pretty straightforward—The roof was first sprayed with an asphalt primer and then covered with sheets of fire-retardant protector board. Two layers of the TouchFlex were then rolled out and affixed by “heat-welding the membrane, fusing it to the protector board and using the same process to seal the seams.” Once that’s all complete, all of the aluminum flashing will be installed and everything will be caulked.
For aesthetic reasons, we’ve also foregone traditional eavestroughs in favour of a parapet with hoppers (or flow control roof drains). These have built-in strainers that will prevent large debris from clogging them, further reducing the likelihood of a leak. The rear downspouts will be connected to a rainwater tank (probably a Rainwater HOG) which will be used for irrigation in the backyard, and the other downspouts will direct their runoff to an underground drainage pit. This pit is also connected to our weeping tile, with the sole purpose of capturing the excess rainwater and allowing it to naturally dissipate into the soil (as opposed to, oh, running back into our house… which has happened to a few or our neighbours). Apparently we have incredibly dense soil that doesn’t absorb water particularly well.
We had also considered a green roof early on, however it was FAR more expensive than we expected. Beyond the plants themselves, you also have to account for the added waterproofing requirements, plus the increased structural demands (waterproofing and drainage layers, plus the soil, plus the plants, plus the water they hold). And let’s not forget that the plants need to be watered on a semi-regular basis, which meant we needed roof access. There are a few lower maintenance solutions, but they were all something we simply couldn’t swing (read: afford).
Post Tags: drainage, green, roofing, torch, waterproofing
Feel free to file this under “things heard from people who have never built a house before” (me), but everybody I’ve talked to has said to avoid torch down roofs at all cost if you live in a climate that gets any precipitation whatsoever. Apparently, they have the highest rate of failure among most popular roof options. My neighbors to the north of where I’m about to start building even said they had theirs re-done three times over ten years before finally ripping the whole thing out and going with the white single-ply membrane stuff, which apparently has worked out perfectly.
Thoughts? Were there advantages to torch down that other options couldn’t provide?
— posted on December 11, 2008From what I understand, there are actually 2 different kinds of “torch down” techniques. The SBS modified bitumen products we’re using are apparently quite good because it’s essentially a rubber membrane that’s “heat welded” at the seams. A similar product can also be applied with an adhesive, but I’m not sure if one installation is better than the other.
There are other types of non-SBS asphalt products that apparently breakdown quickly and don’t perform well in comparison (which is what I’m going to assume is what you’re referring to… or at least I hope it is).
I hadn’t actually looked much into the roofing options prior to writing this post, mainly because our architects simply said “you’ll want a torch down”. I’ve watched enough Holmes on Homes over the years and he’s always used a torch-down product for roofs like ours. Only when I started doing research did I come across sites that said “stay away from torch-down”, which scared the shit out of me. We were already half done at this point, so there wasn’t any turning back. I kept digging and that’s when I discovered the two different methods and thankfully realized we were using the better of the two.
That said, ask me again when we’ve finally moved in and had our first rainstorm.
— posted on December 11, 2008Jeremy: You are probably right about that. I have no idea. Another thing I didn’t like about the torch down method is that it’s black so it absorbs a lot of heat in the summer time when you least want it. Then again, maybe if you live in a climate that is really cold and sunny in the winter, that could be a good thing.
— posted on December 11, 2008One thing you could do to help minimize unwanted summer heat absorption is to apply a liquid rubber coating that’s white in colour to your existing roofing substrate to help reflect heat, not to mention increasing your waterproofing capability as it’ll provide an additional rubber coat on top of your primary membrane. There’s a lot of liquid rubber coating companies out there that say their product can adhere to virtually any type of roofing substrate and can easily be applied with a roller. Sounds like a potential DIY job.
— posted on March 8, 2009