MM&D MAGAZINE, MAY/JUNE 2011:
In my last column I identified warehouse sectors that would be affected in an oil price shock like that of a few decades ago. In this column we look at how to protect those sectors.
Last time, I noted the main areas affected by such a shock would be asphalt and conventional tar and pea gravel flat roofing. Asphalt is produced from petroleum and tar and pea gravel roofing also has a significant petroleum component.
All types of roofing are exposed to aging due to chemical and physical stresses. Smaller isolated problems like abuse, stress concentration, and quality of workmanship can shorten the life of a normal flat commercial roof. Without a maintenance plan, these problems usually go undetected or ignored and that escalates the the damage and price of repairs.
Both asphalt and pea gravel have replacement and new construction cycle elements, with lifespans of around 25 years. Proper design and inspection, maintenance and repair can increase the life of both. Roof warranty programs usually require at least an annual inspection.
Given the wide climate variation within Canada, I recommend at least a twice-a-year (preferably quarterly) roof inspection. This inspection may not require a professional other then your normal building maintenance person. If the inspection reveals problems, a roofing professional can be called to examine further and do repairs.
A full roofing inspection by a qualified professional includes roof membrane, flashings, roof deck, sheet metal flashings, masonry parapet copings and traffic walkways. These components are interdependent when waterproofing a building.
One of the important areas to look at is roof drains and flashing. Drains are critical to proper drainage on a flat roof. They ensure water doesn’t accumulate and cause ponding. In winter, deep snow covers the roof drains so water can’t drain. Even when it does, the freeze-thaw cycle means some water freezes in the drain so even if the water can get into the roof drain, the roof drain is then plugged.
With a lot of flat roofs, eventually that load gets to be too much. It far exceeds the roof’s design conditions, because the roof was made using the principle that the roof drains are free flowing. Some newer buildings have incorporated heated roof drains to help combat this problem.
Detect problems before failure
Even with an ongoing maintenance program a roof will fail over time. The entire roof doesn’t fail at once and advanced inspection techniques can detect problems before they are apparent. The life of older roofs can be extended by a thermographic inspection. Thermography can detect areas that look fine but are leaking. If caught early, these areas can be isolated and patched, extending the roof’s life.
Likewise for asphalt, maintaining it by sealing lengthens its life. Why bother? As water permeates cracks in the material and settles down at the base, its strength is compromised, resulting in potholes. With cold winters, cracks filled with water are also an open invitation to freezing damage. Even at warm times of the year, grass can grow through cracks on the edges of the surface.
If the asphalt has deteriorated so that potholes have formed, the surrounding surfaces should be cleaned with air compressors to remove all debris. Once the area is dry, apply an asphalt bonding agent (glue). This will help ensure new asphalt sticks evenly without separating.
Next, fill the potholes and patch pave any low areas. Once it’s even, resurface the area with hot mix asphalt to the proper grade and slope. This maintenance should last betwen two and four years.
With age, asphalt gets damaged from ultraviolet rays and oil and gas spills. Sealing is effective to renew asphalt surfaces that have become dry and brittle, to seal small surface cracks and surface voids, and to inhibit loss of surface aggregate. Sealing should be done as soon as any of these problems are noted.
Standard oil base sealant will last up to a year. Higher-priced sealants usually add more durability and a longer life. Some suppliers recommend new asphalt is sealed the following spring.
As asphalt becomes older and more used, it loses oil and begins to deteriorate. You can see this as it turns grey. A spray machine puts that oil back into the asphalt and gives it a longer life.
Dave Luton (email@example.com) is a consultant in the greater Toronto area.