How to Prevent Ice Dams and Winterize Historic Homes

Photo: Brian Clark Howard

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Historic homes are distinguished survivors, having sheltered generations of occupants through harsh elements year after year. As hardy as these homes are, it is important to make sure they are ready for winter weather.

Here are some tips for winterizing your home while keeping its historic materials in mind:

De-icing walkways and driveways:
Negotiating icy paths is a big winter concern. Owners of houses with traditional paving may wonder, what's the best way to manage de-icing a walkway, driveway or front stoop to make it less treacherous after a winter storm? It is important to note that frequent use of chemical de-icers can damage historic brick paving, and even more durable surfaces like slate and granite will suffer if de-icers are overused.

The trick here is to use de-icers sparingly, perhaps only de-icing the access to the one entrance you use most frequently. For less used pathways, consider using sand or sawdust for traction. And shoveling early and often is a good way to prevent historic masonry paths and drives from developing an accumulation of snow and ice.

Preventing ice dams:
Ice dams, accumulations of ice at the roof line or in gutters, form when heated air escapes into the attic and warms the roof sheathing, melting any snow that sits on top. Melted snow runs down the roof and re-freezes when it contacts an overhanging, unheated eave line. The weight of an ice dams can pull gutter and trim woodwork off the house. Check for the likelihood of ice dams on your roof by inspecting the roof during the first light snowfall or a heavy frost. Look for an uninterrupted blanket of snow on the roof. If you don't see this, follow the tips below.

To keep ice dams from forming, keep the attic cold. Homeowners should make sure that the attic floor is well insulated and that any gaps to heated areas below are sealed off. Penetrations into the attic from plumbing vents or electrical work should be sealed with caulk, expanding foam, or foam and backer rod. Replacing old, damp, or compressed insulation with new loose-fill or dense-pack cellulose or fiberglass insulation helps to combat ice dams and also keeps down the costs of winter heating and summer cooling. Once the floor is air-sealed and insulated, make sure the attic is vented to move warm air outside before it can heat the roof.

Roof snow and ice removal:
Homeowners have only a few options in removing ice and snow from the roof of their historic home. Where ice dams recur, homeowners can install de-icing tape or cables along the bottom of the gutter, through downspouts and into drain pipes, or at problematic roof valleys or overhanging eaves. These cables carry a heating element through an insulated wire to warm targeted areas. Homeowners can use a long-handled roof rake to reduce the volume of snow. However, this is only recommended for low-pitched roofs, and can be dangerous to attempt on a two-story building.

Chemical de-icers should never be used on roofs since they can discolor shingles and corrode drains, and chopping at ice can damage roof shingles or siding, so it is best to stick to the above recommended methods.

Keep melting snow out:
The last thing a homeowner wants is for an ice dam to force melt water into the house. To prevent recurring ice dams, it may be necessary, when the house is re-roofed, to add an impervious roofing underlayment to a width of at least three feet along the eave line. These installations may not completely eliminate the dreaded ice dams from forming, but can help reduce the damage caused from heavy accumulations of ice.

Sally Zimmerman is the Manager of Historic Preservation Services at Historic New England. For more information on how Historic New England can help you care for a historic home, go to www.historicnewengland.org.

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