This past winter brought unusually heavy snows to many regions of the country, setting the stage for roofing callbacks. Mike Zito, general manager for DiGiorgi Roofing & Siding, Seymour, Conn., says there are three main reasons his company gets a callback. (They are, he points out, "generally unrelated to our work.") Ice damming tops the list.

Ice damming occurs where snow or ice blocks gutters and downspouts, causing water to pool or back up, and sometimes find its way inside the house.

"There might be a section we haven't worked on, and they get an ice dam and figure our new roof is the cause," Zito says. The best defense against ice damming, he points out, is to install an ice and water guard -- a self-sticking waterproof membrane running up under shingles as much as 2 feet over the heated area of the roof. "We also recommend homeowners increase insulation and ventilation to the attic area," Zito says, because escaping heat causes snow to melt.

Callbacks often also involve skylights. Proper flashing while re-roofing forestalls such complaints, except when rain leaks through the frame or around glass. Skylights are problematic, Zito says, but homeowners get used to daylight and are reluctant to remove them. Where leaks develop as a result of a worn or faulty skylight unit, DiGiorgi Roofing & Siding offers a replacement skylight.

Improperly flashed chimneys, or chimneys needing re-pointing or other masonry work, are a third major reason for callbacks. Jerry Rott, sales manager at William C. Rott & Son, Tanawanda, N.Y., recalls a roof replacement job in which company service personnel were called back "12 or 15 times" in a two-year period. The problem turned out to be a chimney that had been taken down to the roofline but never properly capped. As it turned out, Rott's brother happened to be attending a seminar in California where this very same problem was discussed. On returning to New York, company personnel capped the chimney and eliminated the leak.

But hidden leaks, Rott says, "are still our biggest problem," with most leaks the result of improper "flashing and nailing." As an example, Rott points out that nail-gun toting crew members rarely carry hammers, so an errant nail -- sticking out even a quarter inch, say -- will, after a period of time "cause the shingle over the top of that to wear."