Gutters, downspouts and the ground below
Where the water goes when rain hits a Montville roof
A roof gathers more rain than the lawn beneath it ever would, and every gallon has to go somewhere. Below: the arithmetic, the places a downspout can empty, flat roofs that hold water, and what January does to gutters.
Five hundred gallons from one inch
Rutgers Cooperative Extension's water resources program gives a rule of thumb: an 800-square-foot patch of roof draining into one downspout sheds about 500 gallons in a one-inch rain. A typical rain barrel holds about 50 gallons, so a single downspout can fill ten of them in one storm. A 2014 letter on the program's page says barrel distribution was ending for lack of funding, which leaves the arithmetic as the useful part.
That is why a gutter that sags or spills at one corner matters more than it looks. The load from a whole roof section arrives at a single point, and whatever sits under that point takes it.
Down the spout, then where?
The EPA's guide to disconnecting downspouts notes that many drain onto paved surfaces, which can send water into the street. Some connect underground to the sewer or storm drain. Redirecting the outflow to a rain barrel, a lawn or a garden lets it soak into the ground, and Rutgers gives the same advice. The EPA also cautions that local rules and the water's destination deserve a look before anything is disconnected, since the idea does not suit every site. The page carries a notice that it is no longer updated.
Winter changes the picture. Montville's county hazard annex lists sump pump icing discharges as an action, because pumps that empty into streets cause icing during extreme cold. The annex is about sump pumps, but a downspout that empties onto pavement sends water across the same surface.
A flat roof that still holds water two days later
The asphalt roofing trade group draws the line at 48 hours: water still standing on a roof after two days counts as ponding. Rain, snow and runoff from rooftop equipment can collect on a low-slope roof, and debris in the drains adds to it. The group recommends a slope of at least a quarter inch per foot so the roof drains freely. It says model building codes ask for that minimum on new construction and for positive drainage when a roof is redone.
For low-slope roofs the same group recommends a professional look each spring and fall, with leaves and dirt cleared from the drains and gutters. Flat roof work covers what a roofer checks.
Gutters in a freeze
The Building America Solution Center explains an ice dam this way. Warmth from the attic melts roof snow, the water runs to the eaves, and it refreezes on the colder overhang. The growing ridge then dams the next melt and can push water back under the roofing. A University of Massachusetts building technology article makes a point many people miss. Gutters do not cause ice dams, but they gather ice at the eaves, and ice-filled gutters can bend, tear away and pull the fascia and downspouts with them.
The same article advises against heat cable, which it says wastes energy and creates a second dam just above the cable. It also advises against hacking at ice, which can hurt people and damage the roof. For the cause and the repair, see ice dam damage.
When the water keeps coming back
Stains on siding below a gutter run, soil washed out under a downspout, a gutter that pulls away from the fascia after every freeze: describe each one out loud. Gutter repair covers what a roofer can look at, and a roof inspection widens the view to the whole roof edge. Call (862) 430-2399 and tell the roofer where the water turns up.
Before you call
Keep the street address, what you noticed and the roof's age close by, then call (862) 430-2399. If you rent, your landlord decides on roof work, so that conversation comes first. Served: Montville, Towaco, Pine Brook, Boonton and Lake Hiawatha.
