Guide: Repairing the cottage roof
Weather conditions can do a number on the cottage roof. Here's how to make it watertight
Asphalt shingles still dominate 85–90 per cent of the residential market, according to Art Stanfield. He doesn’t hesitate to credit cost advantage for that success. A “square” of economy asphalt shingles, or three bundles, starts at about $50. And application is straightforward enough to invite DIY installation, which is where the real savings come in. It may be false economy if the weekender doesn’t follow instruction to the letter, or drops the ball on the more complicated and more critical business of working around chimneys, valleys, and flashing, but that will be the case with every kind of roof covering.
The basic shingle is a felt mat, saturated with asphalt and coated with granules of crushed rock. The granules are given a coloured ceramic coating before they go on the asphalt. The wide palette of colours gave asphalt an edge in times past when the competition was limited to cedar’s brown turning grey with age, and steel’s grey turning brown with rust.
Asphalt options include a fibreglass mat, tougher than felt but impervious to asphalt. In other words, it can be coated but not impregnated with the stuff. Laminating two mats together can sandwich more weathering asphalt into the shingle, but it costs more and it’s heavier. At the top end are the so-called “architectural” shingles, fat enough to cast shadows at the edges (or have faux shadows coloured along the edges) in order to look more like shakes. In general, the thicker the shingle the more it costs and the longer it lasts.
Longevity is where it gets tricky. First, much depends on roof conditions. As we’ve seen, water retention advances weathering. Where they’re well-shaded and gathering moss, shingles won’t last as long as they might on the sunny, airy side of the roof. A special copper-granulated shingle discourages moss and algae growth, or you can retrofit zinc strips to the roof. It works: Though neither metal will remove existing moss and algae, both will stop further growth.
Then there’s the weather. Philip Steiner had “25-year” shingles installed on his Georgian Bay cottage seven years ago and already finds five or six ripped away each spring. Steiner blames the wind, but his case illustrates the potential gulf between manufacturer, installer, and cottager. The tarred strips across the face of each shingle are hidden under the tabs on the next shingle above. The strips are designed to soften in the sun and seal the two layers together. First, Steiner had his roof installed in October, which might have been too cool for the sun to do its sealing. Secondly, in high-wind areas and cold-weather installations, IKO advises installers to hand-seal each tab with a dab of cement. In high-wind areas, they also call for six nails in each shingle instead of four. And these extra precautions have to be taken during installation, not the next spring when the shingles are flapping in the wind. When installers don’t follow the manufacturers’ advice, any warranty on the materials may be void. The cottager is left to fight it out with the installer.
Ice dams are of particular concern with asphalt. “It’s the biggest complaint in cottage country,” Stanfield acknowledges. The rough surface holds ice on the roof. And if the slope is steep enough to let the ice slide off, it will certainly take some of the protective granules along for the ride. To stop the dam leaks, installers used to apply an impervious ice-and-water shield as an underlay, extending from the eave to 12 inches past the interior wall. Now, six feet is more common, according to Stanfield, and covering the entire roof would be even better. The premium underlay is a bitumen membrane that seals itself to the sheathing and seals around any nails.
This article was originally published on November 4, 2003