Ice dams are a huge problem in the New England area, especially around the Boston Metrowest. Ice dams form when snow on the rooftop melts and then re-freezes at the colder, bottom edge of the roof.  They receive their name because they hold water like any dam does. Your roof is designed to shed, rather than hold, water. When trapped water finds its way under your shingles it can wreak havoc, potentially causing serious damage to the interior of your home. Although gutters can exacerbate the problem, ice dams can and do form without gutters.

The cold facts:

Much of the information about ice dams online leads you to believe they can be thoroughly prevented by properly ventilating your attic and installing sufficient insulation. The theory behind this is twofold: insulation will keep the heat from the rooms below from rising up and causing melting, while proper ventilation will allow cold air into the attic with the goal of equalizing the temperature of the attic with the outside temperature, again, preventing melting. While it is advisable to make sure your home is adequately ventilated and has sufficient insulation, in our experience, even homes with proper ventilation and adequate insulation can still experience terrible ice dams.

Case in point:

2010-2011 was an especially bad winter for ice dams, with many homeowners experiencing leaking. LaBelle Roofing dispatched six crews over a two-week period clearing ice dams and removing snow from roofs. We cleared hundreds of dams that year alone, and what we noticed was that, while home after home had terrible ice dams, nearly all of them also had properly installed ventilation and well-insulated attics.

What is going on?

The truth is that it is nearly impossible to equalize the temperature of the attic with the cold outside air. There will always be some warm air that escaping from the house into the attic area. Nowadays, many homes have heating ducts that run through the attic too, and this can also contribute to melting. If you look at an unheated garage, you will notice that there are no ice dams. This is because there is no heat rising up and melting the snow. The roof temperature is equal to the outside air temperature. Unless your house has windows in the attic that can be opened to sufficiently cool the attic, there is almost always some melting.

Some solutions:

Heating cables can be effective in melting channels through the ice dam so that trapped water can get out and leaks can be averted. Be sure to check the wires for wear annually and have a licensed electrician install these cables alongside a qualified roofer.

Leak barriers, more commonly known as “ice and water shield” are installed when a new roof is put on. These underlayments were designed to help prevent leaks due to ice dams. It is important to note that, while they do go a long way towards preventing leaks, they are not fail proof. Ice and water shields come in several different grades and can range in price from just $50.00 per roll on up to $160.00. When considering new roofing job estimates, take the time to compare apples to apples and get the best quality underlayments you can afford.

Closed cell foam insulation systems have been used effectively in preventing heat transfer and melting. These can be quite expensive to install.

Heated gutters/eaves systems abound and vary greatly in price and functionality.

Professional service:

Ice dams should be left alone if they are not causing leaks. We also advise not removing the snow from your roof unless it is presenting a danger due to weight. When snow is removed using a roof rake, a new ice dam can form where the roof rake reach stops. This area is where your roof has less protection because it is often beyond the reach of the ice and water shield. We strongly recommend calling in a professional as this is very dangerous work. When the dam is successfully opened in the area of the leak, the leak generally stops immediately.

Call LaBelle Roofing, servicing Wayland and the Boston Metrowest, immediately if you develop a leak from an ice dam!

written by

Rob LaBelle


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