Flat roofing has changed considerably over the years. Traditional tar and gravel roofs were once commonplace throughout Vancouver and the Lower Mainland, while newer single-ply membranes such as TPO became increasingly popular as a faster and less expensive alternative.
In fact, for a while, we recommended TPO and promoted it in an earlier version of this article.
However, our experience at Absolute Roof Solutions has led us in another direction.
For flat and low-slope roofing applications, we now prefer a two-ply torch-on modified bitumen roofing system.
Why we moved away from TPO
TPO, or thermoplastic polyolefin, is a single-ply roofing membrane. The sheets are installed over the roof, and their seams are welded together using hot air. It has many attractive characteristics, plus it is inexpensive and easy to install.
However, based on our past installation experience with TPO, we had warranty issues even on properly installed roofs, particularly involving seams. Based on that experience, we decided that torch-on modified bitumen provided the type of roofing system we would rather install for our customers.
We simply believe this is a better choice for the roofs we encounter in Greater Vancouver.
The advantage of two-ply Torch-On Roofing
Torch-on roofing uses modified bitumen membranes rather than a single sheet of thermoplastic material.
A typical two-ply system consists of a base sheet and cap sheet. During installation, heat melts the surfaces of the modified bitumen membranes, fusing them together.
That gives the roof something we particularly value: redundancy.
With a single-ply roof, one membrane provides the waterproofing layer. With a properly installed two-ply torch-on system, two layers protect the building.
Torch-on modified bitumen is also a mature roofing technology with a long track record in Canada.
For Vancouver buildings that must endure months of rain, standing water, leaves, debris and repeated wet and dry cycles, we believe that proven track record matters.
What about grease and rooftop contaminants?
Another consideration for commercial buildings is what may end up on the roof.
Grease, oils and other contaminants discharged from rooftop equipment can adversely affect some single-ply roofing membranes. This can be particularly important for restaurants and other commercial buildings with kitchen exhaust systems.
The roofing system therefore needs to be selected not simply by installation cost, but by how the building is actually used.
Better than tar and gravel
We also recommend torch-on modified bitumen when replacing an aging tar-and-gravel roof.
Traditional built-up roofs can provide long service, but installation is labour-intensive and messy. Finding leaks can also be difficult beneath layers of gravel.
Torch-on provides a cleaner, modern membrane roofing system while retaining the advantages of a durable bituminous roof.
Our Choice Is Based on Experience
Many roofing products are on the market, and manufacturers understandably promote the advantages of their particular systems.
Our recommendations come from something different: installing roofs and then seeing how they perform years later.
Based on that experience, Absolute Roof Solutions prefers two-ply torch-on modified bitumen roofing for many flat and low-slope roofs in Greater Vancouver.
So if your tar and gravel, TPO or other flat roof needs replacement, contact Absolute Roof Solutions for an assessment and recommendation based on your particular building.
