Understand options before choosing a roof
Sometimes the hardest part of getting a new roof is making sense of all the details different contractors recommend. And while it’s true that there’s more than one way to get a rainproof roof, a little knowledge helps a lot when it comes to assessing the many options.
The first thing to understand is the value of a durable roof underlay, though this is often forgotten or under-appreciated. There’s nothing new about how this flexible sheet material is often used to make roofs more reliable in leak-prone areas such as eaves, but there’s more.
The best roofers also install some kind of membrane over the entire roof these days. “That’s overkill,” some contractors will tell you. Well, not when you look at the big picture.
Weather is getting more extreme, even here in Canada. More frequent hurricanes, tornadoes and ice storms are even prompting insurance companies to push for higher technical standards, including those for roof construction. And there’s no better way to build a bulletproof roof than by installing a waterproof layer before your shingles go down. You’ll be glad you did when the next weather event tears off half the shingles in your neighbourhood.
If you’re installing asphalt shingles, understand the value of zinc as a moss preventive. Rooftop growth shortens shingle life significantly, but you can stop it before it starts using strips of sheet zinc installed near the ridge. Just a couple of inches of exposed metal releases tiny amounts of non-toxic zinc oxide into rooftop run-off — enough to keep six metres of roof surface clean, even in shaded, north-facing, forested locations.
Zinc roofing strips used to be hard to find, but not anymore. Most building supply outlets carry it. Contractors don’t benefit personally from a roof that lasts 40 years instead of 30, so you really can’t expect them to suggest zinc on their own.
You should also understand that every roofing option fits into one of three categories: shingles, sheets or tiles.
Simplifying a universe of options into a trio of broad categories isn’t going to help you choose between granite grey and sierra brown, but it will help you settle on a roofing system that makes sense for the house you’ve got.
Shingles are made to fasten to wood sheathing and a metal roof is best anchored to strapping. Authentic tiles need a much beefier roof frame than normal to support the extra weight.
Besides these options, perhaps the biggest roofing decision you have to make involves the rivalry between organic asphalt shingles and fibreglass shingles. Both look the same on a roof, though there are significant differences behind the scenes.
Organic shingles are the traditional choice in Canada. They use a felt substrate to support the tar and gravel that forms a weatherproof layer. Fiberglass shingles, on the other hand, originally worked their way up from the United States because they offer several advantages. They use similar tar-and gravel coatings, though these are made over a fibreglass substrate instead of felt.
Fiberglass shingles are also physically thinner than asphalt and more heat resistant.
If you’re shingling a cathedral ceiling or any other roof without enough ventilation to keep the surface from getting super-hot, then fibreglass is definitely the way to go.
The first waves of fibreglass shingles to arrive in Canada more than a decade ago were ill designed for our cold climate and failed prematurely.
This created a bad reputation that’s outlived the reality. Today’s best fibreglass shingles offer 40-year, 50-year and even lifetime warranties and carry the highest fire-resistance ratings.
Based on experience, fibreglass shingles are my first choice for a new asphalt roof.
While there’s no perfect roof, there is one thing that’s universal. Most of the cost of a new roof is labour, so the longer you can make it last, the more economical your new roof will be.