Roof Talk-101 No Two Gutter Systems Are The Same

Roof Talk-101   No Two Gutter Systems Are The Same

No two buildings — or gutter systems — are exactly alike. Whether it’s a shopping mall or country club, a large estate or a neighborhood home, every guttering project has specific needs. And though 5- and 6-inch gutters are industry standards, factors ranging from architecture to geography can affect decisions about proper sizing.

“Start by looking at the roof line,” advises Bruce Andrews, owner of Bruce Andrews Seamless Gutters/Gutter Helmet in Maiden Rock, Wis. “When you see the number of squares of shingles, it will tell you how many gallons of water can come off of the roof during a storm. The bigger the roof the more water it will generate.”

Since gutters exist to drain water away from buildings, then estimating the amount of water a gutter must potentially carry is a key to determining the correct size for the trough. But Dan Vitale of Vitale Seamless Gutters in Somersworth, N.H., says in addition to the size of the roof, “Slope is another important factor to consider.” His own rule of thumb is 6-inch gutters for most commercial projects and 5-inch for most residential jobs. Yet different conditions may require an adjustment in gutter size.

A third consideration is the downspouts. “You should worry more about your downspout sizes rather than your gutter size,” advises owner Doug Craig of Viking Metal Products in East Point, Ga. Happily, he points out, the first chapter of the Sheet Metal and Air Conditioning Contractors National Association (SMACNA) gutter manual “has in detail the maximum rainfall for locations around the country, so that you know how many square inches of rainfall to plan for each downspout.”

Size-specific solutions
Since Andrews’ crews perform both residential and commercial work, they must know what to look for at each jobsite. Based on the SMACNA manual’s data regarding expected rainfall, he notes, “We might see that 5-inch gutters need an extra-large downspout. In the Midwest, for example, you can have everything from a steady all-day rain to a half-inch downpour in a few minutes.”

After sizing up the gutters, Andrews continues, “When we get to a house, we make sure the drainage is right.” Even if gutters are the correct size for the project, an improperly installed gutter system can cause overflows, backups, blockages, ice damming and other problems.

Andrews has also encountered projects where the steep pitch of the roof necessitated extra downspouts. Yet the decision is not always cut-and-dried. “Whenever possible, we hide the downspouts and try to keep the aesthetics of the building in mind,” he explains. One way to balance function and appearance, he suggests, is to “maintain the look the customer wants by using colors that match as closely as possible, so that the work blends into the building.”

The demands of form and function sometimes require a combination of 5- and 6-inch gutters. “We’ve done some large sheds and used 5-inch gutter on smaller overhangs and then 6-inch for longer runs,” Andrews reports. “But since the different sizes weren’t installed close to each other, it maintained the look of the building.” Depending on the job, Bruce Andrews Seamless Gutters might use larger downspouts — or more downspouts — for the bigger gutters on a job where both 5- and 6-inch styles are used.

Whatever size gutter is needed, Andrews adds, “You must have a splash guard for every valley.”

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