Snow and ice raise havoc with houses - or at least people think they do.
So, what to do: Shovel? Heat the attic? Make the attic cold? Insulate? Ventilate? Not necessarily any of those.It's a safe bet that 99 percent of houses in New England will hold more snow than Old Man Winter can throw at them - several feet worth, in fact. Most houses in the North are built with snow in mind, and their roofs are steep enough to hold heavy weights or to allow snow to slide off. Even a fairly gentle slope will handle snow. So will a flat roof.
After all, roofs already hold the weight of asphalt shingles or slate, which can weigh up to 30-plus pounds per square foot. And many hold two layers.
Snow weighs about 5 pounds per square foot, 12 inches deep, depending on water content. About 12 inches of snow equal 1 inch of rain; a cubic foot of water weighs 62.4 pounds; divide by 12 (1 inch) and you get a shade over 5 pounds per square foot of rain, 1 inch deep.
Five pounds per square foot is hardly anything added to a roof, considering what is already on it.
Some houses were designed in sunny California with long-spanned roofs, with little slope. In that case, it might be prudent to sweep or shovel off some of the snow. But not necessarily all of it. Trying to get down to the shingles is not necessary but is a good way to ruin the shingles.
Even a little removal may not be necessary if you don't see any signs of sagging beams or depressed areas. It is probably a good idea, however, to shovel off a dead-flat roof, or one with virtually no slope at all, or at least remove some of the snow.
Snow melting on a flat roof produces a lot of water, which is not only heavy but if the snow (or ice) blocks the drains, the water could stay longer than it should.
There is not a lot you have to do if you get ice on the roof, either. Ice will form on a roof sometimes, especially on the gutters. But there still is no problem because water will cascade over the gutters. The biggest hazard is icicles, caused by that cascading water freezing; if they are big enough to skewer an unsuspecting cat or dog when they fall (it has happened), then knock them down before they get too big.
So why are so northerners concerned about snow and ice? It has been around for centuries, without much harm.
It's the dreaded ice dam that can form under snow, backing up water to leak into attics, between windows and into the house, raising all kinds of havoc and driving insurance companies to distraction.
Yes, but those ice dams don't occur on all houses, only those where the attic is warm because it is unventilated and uninsulated. A house with a warm attic has a warm roof, and it is this warm roof that causes ice dams.
Look around your neighborhood on a pleasant day, when the snow is quite deep. Most houses will have a good mantle of snow on the roof, indicating that the attic floor is properly insulated and well ventilated. The attic is cold, and the snow stays on the roof.
Some houses, however, have bare roofs, indicating warm attics and warm roofs, which melted the snow very quickly.
It is these houses that are most likely to get ice dams. Snow builds up, and then starts to melt from the bottom up, the wrong way; a cold snap freezes this water, creating the dreaded dam, which blocks water running down the roof under the snow; this blocked water backs up and gets under shingles. You know the rest.
In that case, it is wise to shovel off any snow, until you insulate the attic floor and ventilate the attic. Snow must be cleared from the entire roof, not a pleasant task. If you clear off, say, 6 feet up, you can get the ice dam right at the snow line.
A more permanent cure is to make the roof cold. And that is done by insulating the attic floor and ventilating the attic. The little vents at the ends of the attic at the top of the gable are sometimes inadequate to vent an attic.
What is needed for good ventilation are a ridge vent and soffit vents, the vents on the underside of the overhang.
With proper venting and insulation, there will be a lot of snow, maybe, but no ice dams, no leaks, and no need to shovel the snow.
Another "cure" for ice dams is not really a cure but a way to prevent leaks from ice dams. That is a strip of rubberized material (one type is called Ice and Water Shield) 3 to 6 feet wide and placed along the eave edge of the roof, under shingles. This simply prevents dammed water from getting under the shingles and into attic, house, and between windows.
A cold roof is a better method.
If you have a furnace in the attic, your luck has just run out. Even well insulated, a furnace and ductwork will still lose heat to the attic, and you can't insulate against an open flame. The only cure is to relocate the furnace and ducts.
Another reason you might want to shovel snow from a roof is to prevent the snow from building up, then suddenly slide off in great chunks, imperiling unsuspecting passersby or yourself and loved ones.
This avalanching does not occur on roofs, even steep ones covered with asphalt shingles, because the little pebbles tend to hold the snow until it melts.
But avalanching is definitely possible on roofs with slate, barrel tiles, metal, and other hard, smooth materials. But instead of shoveling it off, you can do something that will keep the snow from avalanching.
And that something is to install snow hooks, which look like little railings and are common on slate roofs.
Vermont Slate & Copper Services of Stowe, Vt., makes and installs Snowguards (that's the company's name for the little railings).
They can be installed in new construction and retrofit projects, on virtually any kind of roof. Call 800-766-4273.