Is roof rejuvenation worth it in Victoria? What the evidence says

Rejuvenation was developed for roofs that age by drying out: years of sun bake the oils out of asphalt, the shingle turns brittle, and granules let go. That is the main way a roof fails in a hot, dry climate. It is not the main way a roof fails here. In Greater Victoria the usual story is shade, fir needles and moss holding water against the shingle through a long wet season, and a treatment that restores flexibility does nothing about moss.

We found no published price for rejuvenation in Greater Victoria, and no dealer for the best-known brand on Vancouver Island. Several local companies offer a treatment of this kind. The prices on this page come from companies in Surrey and North Vancouver, which is the nearest published evidence.

Published prices in BC are about $1 per square foot of roof from one Surrey company, and $1.24 to $2.50 per square foot by product tier from one North Vancouver company. On a typical two-storey house that puts a treatment in the low thousands of dollars. The product's maker describes it as costing up to 80% less than replacement.

That comparison is only fair if the alternative really is replacement. For a 2,000 square foot two-storey home in laminate asphalt our pricing model puts replacement at about $6,900 to $12,600 before GST. If a roof has ten good years left, the alternative to treating it is not replacing it; it is leaving it alone and keeping it clean, which costs far less than either.

The document most sellers point to is a technical report from Ohio State University with a commercial laboratory's results attached. It is worth reading in full, because it is more careful than the marketing built on it. It states that it was prepared at the request of the product's maker and the Ohio Soybean Council and funded by a grant from that council, and that discussion of a product is not an endorsement by the university.

The test used three-tab shingles taken from one 17-year-old roof in Ohio, treated and left to dry for three days. Flexibility improved, and the weight of granules knocked loose fell by 46%. But the laboratory's own tables show the treated samples still lost more granules than the standard allows, and failed the hail impact test at all six locations, the same result as the untreated samples. The fire test was the laboratory's own method, not the standard one. Nothing in the report follows a treated roof through a winter, let alone five years.

The Asphalt Roofing Manufacturers Association states that it strongly advises against the field application of any type of coating or rejuvenator over installed asphalt shingles, and says there is limited documentation of the benefits. Bear in mind who is speaking: its members sell new shingles.

On warranties, the claim you will read online is that treatment voids the warranty. The warranty texts we read are narrower than that. Owens Corning and BP exclude damage caused by coatings, and IKO excludes damage from chemicals including oils. None of them says the whole warranty ends, and none uses the word rejuvenator. The practical meaning is that if a treated roof fails, expect the manufacturer to ask whether the treatment caused it. If your shingles are still under warranty, ask the manufacturer in writing before treating them.

Taking the sellers' own conditions at face value, the treatment is meant for shingles that are intact and in good condition. That narrows the field considerably.

• It might be worth a look on a mid-life roof in full sun, with no leaks, no missing shingles and most of its granules, where the owner understands the evidence is short-term.
• It will not fix a leak. Leaks come from flashing, penetrations and damaged sections, and the seller's warranty excludes them.
• It will not replace granules that are already in the gutter, and granules are what protect the asphalt from the sun.
• It will not remove moss or stop it returning, which is the common cause of early failure in shaded Victoria roofs.
• It is not a way to put off replacing a roof that is already brittle, curling or past 20 years.

If you are considering it, these questions separate a careful company from a sales pitch.

• What exactly does the warranty cover, in writing, and who stands behind it if the company closes?
• Will you inspect the roof first and tell me if it is not a candidate?
• What field evidence do you have from roofs treated five or more years ago in a wet coastal climate?
• Has my shingle manufacturer approved this, and can I have that in writing?
• Do you carry liability insurance and WorkSafeBC coverage for work on my roof?