Guide: Repairing the cottage roof
Weather conditions can do a number on the cottage roof. Here's how to make it watertight
When it comes to the cottage roof, early signs of aging may be hard to spot. Invisible leaks can start rotting rafters long before the first drip hits your head; and an all-too-visible spring dribble from the ceiling may signal ice under the roof, not water coming through.
Inspecting for roof damage
Too many trips onto the roof can cause more damage than it prevents, so combine a regular roof inspection with chimney cleaning or the gutter sweep-out. Avoid hot summer days when asphalt shingles are soft, and cold winter days when they’re brittle. Avoid any roof when it’s slippery or when you’re alone at the cottage. Remember shoes with a good grip, ladder tied off at the eaves, insurance premiums paid-up, don’t touch the wires, yadda yadda yadda. And if that sounds like too much trouble, find a reliable local roofing contractor and a darned good pair of binoculars to inspect what you can see from the ground.
If a leak has prompted the inspection, start inside: in the attic or truss space. Follow the damp to its highest point and, roughly, identify the entry area. It’s a rough guess because the water likely took a less-than-direct route through various layers of shingle, underlay, flashing, and sheathing. From inside, you probably won’t see a hole and blue sky. However, if you know, in general, where water is coming in, once you’re on the roof you can have a closer look at the suspect area.
The most vulnerable parts aren’t the regular roof surfaces but the seams, along valleys and dormers, or wherever chimneys, guy wires, plumbing stacks, and vents break the surface. Some such interruptions may be sealed with metal or rubber flashing. Others are simply daubed with black goo that — for lack of a chemistry degree and the patience to nitpick brand distinctions — we’ll nickname tar.
You’re looking for loose or corroded flashing, and cracks or gaps where “tarred-together” seams have separated. “Water infiltration through a newer roof is probably coming through the flashing,” suggests Art Stanfield of IKO Industries, a major asphalt shingle producer based in Brampton, Ont. “I’d look at the chimney first, and then the valleys.” In most cases, flashing will be “shingled” into the roof: overlapped by roofing higher on the slope and, in turn, overlapping the regular roofing down-slope. But even a shingled flashing can fail if wind or ice dams push water up under an unsealed edge.
Stanfield’s choice of words is worth noting. “Infiltration” means water coming through the roof. Water can also condense against the underside of a cooler roof, building up in layers of frost that melt and drip through the ceiling when you heat the cottage in spring. This is not infiltration but a venting problem, something Stanfield insists is the number one cause of roof failure. It is especially critical in cottages where periodic winter visits charge the indoor air with humidity that will condense on any cool surface when you turn the heating down and leave.
Intermittent heating can also exacerbate ice damming, especially in cottages. The cold cottage collects snow on the roof. A weekend visit with a roaring fire and little insulation heats the roof and melts the snow. When the run-off reaches the eaves – which aren’t heated by inside air — the water refreezes, builds up behind this dam, and eventually rises up under the shingles and through the roof. Re-shingling alone won’t solve the problem.
All of which is to say that the roofing material itself may not be the problem. It is, however, the most visible part of any roofing system and the part where signs of aging are most easily seen.
This article was originally published on November 4, 2003