Most of the time, weather isn't too much for a roof to handle-if the roof is properly installed. You can save yourself and your homeowner clients the headache of weather-induced roof failures by following manufacturer specs and industry best practices during installation.
Here are a few tips from the field:
In hurricane-prone areas, building codes ensure that roofers take extra care to choose sturdy shingles and fasten them securely so they won't blow off when the wind whips to a forceful speed. Still, exposure to even milder wind can loosen nails and sweep debris onto shingles, which damages them over time and leaves them vulnerable to future gusts.
In any climate, roofers can prepare a house for high winds by:
- Securing the roof's edges all the way around the perimeter of the house. Mark Kelly, author of American Roofing: Roofing in America, notes that wind slams the hardest against a roof's corners, so roofers often bolster them. But wind hits with only slightly less force on the roof's edges, where it might not lift the roof, but could peel it. "You don't want to have weak detail on the edge," advises Kelly, whose consulting firm, RMX Corp., is located in Boston.
- Using enough fasteners. Joan Crowe, director of technical services for the National Roofing Contractors Association, says it would take a "hurricane or a microburst" to lift a roof off of a house-unless it isn't properly fastened. But Douglasville, Ga., roofer Joseph Vann Hamby says too many installers skimp on nails to save time and money. He shoots a minimum of four nails into each shingle and urges others to follow manufacturers' recommendations for quantity and spacing to the letter.
- Installing self-stick roofing underlayment instead of standard roofing underlayment to prevent water intrusion during a wind-driven rain.
- Nailing in the nail line. Hamby says he saw an asphalt roof "sliding off the house" after an especially fierce wind-and-rain storm last year, and he blames the installer for cranking the air pressure up too high on the nail gun. Shooting a nail too deep into a shingle can puncture its fiberglass mat so the nail isn't flush with the granules. That creates a hole that will prevent the fastener from holding onto the shingles, he says.
Ice and Snow
Last winter dumped unusually heavy snow even in areas that rarely get it, catching homeowners-and their roofs-unprepared. Tulsa, Okla., roofer Brent Toggle says installers can prevent future snow-season surprises by looking at every new roof with "the mindset that we're going to have 5 feet of snow sitting on it."
To that end, contractors can prepare for ice and snow by:
- Installing a self-sticking underlayment designed as an ice and water shield. Installed at penetrations and at eaves where melted ice and snow tend to refreeze, it adheres to the sheathing and self-seals around nails to prevent water from moving behind it.
- Adding an ice-dam protection membrane. The NRCA recommends this wherever the average January temperature is 30 degrees or lower. The membrane starts at the eaves and slopes upward 24 to 36 inches, depending on the roof's slope.
- Carefully attaching flashing at the roof's edges and corners to prevent melting snow from seeping underneath.
- Ventilating the attic and installing extra insulation on attic floors to lower attic temperatures. The closer the attic and outdoor temperatures match, the less likely ice dams will form. Building codes require attic ventilation in new homes, but Hamby says some homeowners balk at the price when they're re-roofing.
- Protecting a sloped roof with snow guards. The metal or plastic guards "stop snow from coming off the roof like an avalanche," says Jerry Lange of M&D Enterprises, a Boston-based independent sales rep for manufacturers of roofing and waterproofing products.
- Pitching a flat roof toward a drain by about 1/4 inch. Kelly notes that some Northern building codes advise against "dead" flat roofs with no pitch.
Constant exposure to sun and heat can prematurely age a roof and shorten its life. Kelly recommends that Southern pros choose products designed for the local weather. "Some products perform better in heat than others," he says.
In addition, builders and remodelers can work with roofers to slow down heat damage by:
- Choosing a membrane with additives to help it take the heat.
- Sticking with "cool" colors like off-whites or "cool" roofing systems designed to reflect heat rather than absorb it.
- Considering a flat, foam roof instead of a sloped, shingled roof. "Foam seems to be better with the heat," notes Daryl Moore, general superintendent of Lyons Roofing in Phoenix. The sprayed-on polyurethane foam is protected by an elastomeric coating that shields it from ultraviolet rays.
- Ventilate the attic to lower its summer temperature. That can cool off the roof deck, slow down aging of the roofing material, remove excess moisture from the attic, and cut the homeowner's air conditioning bills.
Leaky roofs are a homeowner's greatest roofing headache-and the contactor's, too, if the roof leaks while it's under warranty.
Roofers can prevent many leaks with special attention to flashing and sealing during installation by:
- Using a multiple-layer polypropylene/polyethylene underlayment designed as a water barrier. Many are self-adhesive and self-seal around nail holes and other penetrations, and come with manufacturer warranties. For traditional underlayment, overlapping horizontal and vertical seams will make it more leak-resistant.
- Installing drip edges. Although Hamby says "very few" Georgia roofers use drip edges on houses with pronounced overhangs, the metal devices, installed at the eaves on top of the sheathing, protect the edge of the sheathing. They also allow runoff from the roof to drip into the gutters and prevent rain from getting underneath the roofing material.
- Step-flashing where a sloped roof meets a vertical wall-at a chimney, a dormer window, or a lower roof. Water can pool there or leak through the roof into the home. Hamby says chimneys are notoriously leaky because of poor flashing. He recommends step-flashing a sloped roof with metal 5 inches up the "warm wall." Kelly recommends 8 inches.
- Inspecting flashing during and after installation. Flashing creates a watertight layer between roofing materials and the house or between intersecting parts of the roof and are blamed for many early leaks in roofs.
- Springing for high-end drains. "My pet peeve with all of the world of flat roofing is the roof drain," says Kelly. "All of the water on the roof goes to the roof drain, so you'd better put in a Cadillac roof drain. You wouldn't want to cheap out there" by skimping on flashing or poorly integrating the roof with the plumbing system.
- Following manufacturer's instructions. "It's taken them years and years to invent them and it takes a roofer sometimes five minutes to screw it up," notes Moore. "If you have any issue with the roof, you have recourse to go back to if you follow the instructions."
Sharon O'Malley is a contributing editor to Building Products magazine and ebuild.com.