by: The Great Canadian Roof Doctor

Last updated November 13, 2017

Durability is the ability to withstand wear, pressure, or damage. Durability is not covered in the warranty of any shingle manufacturer. What is covered … is the degree to which the manufacturer meets its own standards of uniformity. They warrant against “manufacturing defects”; but even then … only if your shingle has a leak, and only if it meets several other conditions.

Manufacturing shingles is a straight forward automated process that produces an extremely uniform product, that has essentially no defects caused by the manufacturing process. A manufacturing defect occurs if a shingle is manufactured outside the self-imposed limits that a manufacturer sets for its own manufacturing process.

These limits can include measurable parameters such as: the allowable deviation in shingle size from intended, or the minimum amount of granules on the shingle surface at the time of packaging, or the min/max allowable weight of a packaged bundle of shingles. With flexible enough limits, you should not expect to ever see a shingle with a “manufacturing defect”. The manufacturer does not publish its current self-imposed limits; and interestingly, it’s the manufacturer that decides whether or not your shingle has a manufacturing defect.

Durability has become the responsibility of the end user. Here’s a quote from one shingle manufacturer’s current warranty … “The Limited Lifetime Warranty does not constitute and should not be interpreted as a statement or representation as to the durability of BP shingles.”

The increased durability achieved by “Weatherproofing” (the deep cleaning, and subsequent non-toxic sealing of existing installed asphalt shingles) is covered by The Great Canadian Roof Doctor, with a warranty that guarantees no surface degradation. To accommodate the possibility of us weatherproofing shingles that have already degraded internally due to poor ventilation, choice of materials, or due to poor installation methods … we restrict our warranty to 10 years from the date of application. Our experience to date is that all of our weatherproofed roofs are currently unchanged from the condition and appearance that they had, a day after we sealed them.

We warrant that the sealed surface will not deteriorate due to the effects of sun, rain, ice, snow, salt, hail, moss, algae, or from any combination of these. We also warrant that our protective coating will adhere to the asphalt shingles, and to the granules on those shingles, and we further warrant that there will be no loss of the shingles’ protective granules.

For original or replacement roofs that we install ourselves (where we control the quality of the roofing job) and seal soon after installation, the same warranty applies … but for a period of 50 years, and with an expectation that the shingle life (durability) will extend well beyond the 50 year warranty period. If an existing roof is of the same quality that we install, then similar performance from Weatherproofing can be expected.

Properly installed (but un-sealed) shingles will break down from the outside, and will generally see an expensive “re-roofing” in about 15-20 years, with the variations in timing usually due to the local environment.


Bob Cassady, P.Eng.
District Sales Manager – Mid and North Island
The Great Canadian Roof Doctor Inc.
778.992.1922 – direct Comox Valley line
1.888.677.6310 – toll free

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