What You Need to Know About Cold-Climate Flat Roofs

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Stylish, modern, and efficient—flat roofs hit a lot of items on your home bucket list. But they also come with a reputation for leaks, cracks, and collapse. While not frequent, per se, the low slope of a flat roof does make it more prone to certain problems, particularly when it interacts with the elements. Excessive rain, heavy snow, and built-up ice all pose extra challenges for flat roofed homes.

Unlike pitched roofs, low-slope buildings don’t have the benefit of gravity working in their favor to remove precipitation off the surface. Instead, flat roofed structures must rely on effective drainage systems and strong building design to keep them from leaks and other destruction. Here are all the ways weather affects your flat roof—and what you can do to prevent problems down the line.

snowy flat roof home

Your Installer’s Expertise Matters When it Comes to Leak Prevention

Because flat roofs require specialized materials and construction methods, any roofer you choose to work on yours should have a large resume of past work on flat roofs. For instance, a worker who doesn’t have a lot of experience with flat roofs may not understand how to apply waterproof sealants. Often, the end result is tiny pinhole-sized punctures in the seal, which, although small, can do a lot of damage.

In fact, a lot of the time when a flat roof starts leaking, the root of the problem is one of these tiny puncture marks. Hiring a professional who knows their stuff will save you this potential headache—good news if you live in a wet or snowy climate.

Dropped Leaves Can Clog Gutters—Leaving Water to Pool on Roof Surfaces

Every home relies on its gutters—they help funnel rainfall and melted snow away from your roof and siding, and that’s true no matter what kind of roof you have. But in flat roofed homes, they’re extra important.

Most flat roofs are essentially designed like a swimming pool, so if your drainage system isn’t functioning well, it can cause water to pool on the top of the roof. That’s a problem for a couple of reasons. For one thing, it makes you more prone to leaks. For another, it adds weight to roof surfaces—and water isn’t exactly light. A cubic inch of water weighs about 0.036 pounds. Multiply that by the surface area of your roof, and you could easily have a thousand pounds of extra weight for each inch of water. Lastly, standing water can wear down your roof’s membrane, meaning you’ll have to make repairs—or even replace your whole roof—more frequently.

This problem is best solved with an ounce of prevention. All you need to do is maintain your gutters. Clean your gutters and scuppers out with a trowel and hose at least twice a year—or even more frequently if you want, particularly after a bad storm.

You can also sweep your roof off with a broom—it will keep your drains free and clear and your home looking nicer to boot!

flat roof home

High Winds Also Create Problems

For flat roofed homes, wind is a special concern, as well. Unless your builder takes proper precautions, wind lifts can occur—that’s where the roof of your home is literally lifted off its mechanical fasteners.

This usually happens when the installer uses the wrong kind of nail or screw to attach the roof material in place—in fact, sometimes, roofers may only use staples, which is not appropriate at all. If you’re in the market to have your flat roof replaced and you live in an area with high winds, make sure to ask your installer how they plan to prevent lifts.

Ice Dams Can Form When Flat Roofs Are Not Properly Insulated

In most flat roofed homes, heated spaces are situated directly under the roof, without any buffer from an unheated attic. This can wind up causing problems with ice dams, which is what happens when heat transfer from a home’s interior melts the snow on a roof—which then refreezes as it makes its way to the outer edges of the roof’s surface, where it is colder.

Ice dams almost always indicate problems with insulation or ventilation. The good news is that if you have a flat roof, you should be able to add rigid foam insulation under the surface to prevent ice dams. Rigid foam typically insulates more effectively than fiberglass—and improves heating and cooling efficiency, as well. Another idea is to have your roofer install an ice-and-water shield during a reroofing project—that’s an impervious membrane underlayment that protects your roof from the effects of ice and rain.

Altogether, you may have to take some special care with your cold-weather flat roof, but then again, all roofs need maintenance to keep them in good shape, no matter the style or climate. So let the elements do their worst!

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