A roofer gave you a price. An applicator gave you another, five times lower. Both sounded sincere. Here is how to sort it out without relying on either one's word.
What each option actually costs
Start with public numbers, because that is the only solid ground.
| Option | Cost per sq ft | Typical single-family home |
|---|---|---|
| Replacement, asphalt shingle | $6 – $12 | $9,500 – $16,500 |
| Replacement, metal roof | $15 – $30 | $22,000 – $45,000 |
| Replacement, elastomeric membrane | $11 – $21 | Varies |
| Surface treatment | Quoted on inspection |
Those prices include tear-off, disposal, materials and the labour of a roofing contractor. Add $75 to $120 per sheet if the decking needs replacing, and $250 to $500 per roof vent.
The calculation nobody runs: percentage of your home's value
The average single-family home in Saguenay–Lac-Saint-Jean was worth $243,516 in 2024. A $9,500–$16,500 replacement therefore represents 4% to 7% of your property's value.
The same job on a $600,000 Montreal home is 2% to 3%. Same dollars, very different weight in a household budget. That is precisely why the question "can we buy time?" carries more urgency here than elsewhere.
Three cases where you replace, no hesitation
- The decking is compromised. If the plywood under the shingles is soft, buckled or rotten, no surface treatment on earth changes anything. The problem is structural.
- It already leaks. Active water intrusion signals a mechanical failure: lifted flashing, punctured valley, backed-out nail. It has to be opened and repaired. A treatment applied over a leak is money thrown away.
- The shingles are brittle or lifting. Take a shingle corner and bend it gently. If it snaps instead of flexing, the asphalt has lost its oils past the point of return.
Three cases where treatment makes sense
- Your roof is 8 to 22 years old and still watertight. That is the window. You may see granules in the gutters, some moss on the north face, uneven fading, but nothing is getting in.
- You have a 5-to-10-year horizon in the house. Pushing a $14,000 expense back several years has real financial value, especially if you plan to sell.
- Your insurer is starting to ask questions. A maintained, documented roof defends itself far better than one nobody has climbed in fifteen years.
The question is never "treatment or replacement" in the abstract. It is "where is this specific roof, today". An honest diagnosis beats any brochure.
How to assess your own roof in ten minutes
- Look in your gutters. A heavy build-up of granules signals advanced shingle wear.
- Look at the south face. It takes the most UV. If corners are curling, the clock is running.
- Look at the shaded areas. Moss and lichen settle where moisture lingers, usually under trees or on the north face.
- Look in your attic. Staining on the wood, a damp smell, compressed insulation: more reliable signals than anything visible from the ground.
- Find the installation date. Deed of sale, an invoice, a pre-purchase inspection. Exact age changes the entire reading.
The warranty question
It deserves a straight answer. Several shingle manufacturers explicitly exclude products applied after installation. BP excludes "any exposure to paint, inadequate cleaning solutions, coatings, chemicals". IKO excludes the effects of chemical reactions with the shingles. The Asphalt Roofing Manufacturers Association formally advises against applying coatings over installed shingles.
In parallel, the legal warranty under Quebec's Consumer Protection Act applies independently of any contractual warranty, and requires that goods serve their normal use for a reasonable time. Some applicators conclude from this that a manufacturer can void nothing in Quebec. That is an optimistic reading: to our knowledge, no published ruling confirms it.
Our position: if your roof is still under an active manufacturer warranty that has real value to you, that conversation belongs before the work, not after.
In short
Replacing a roof resets the clock to zero, the only option once the structure is compromised, and entirely legitimate. Treating a roof buys time on a still-sound asset at a fraction of the cost. Both are defensible. What is not defensible is choosing without anyone having climbed up to look.