Who to contact to deal with ice-dam grief?
Removing snow from roof is remedial action, but underlying source of problem must be fixed

Sun Mar 4 2007


QUESTION — I had a problem last winter with my kitchen ceiling leaking. I have a one-and-a-half-storey house and had a major ice dam problem in that area.

While I understand to some degree what the mechanics of the causes are, my problem is that I do not have any idea what kind of tradesperson to contact to fix it. A “handyman” I used at one time added some insulation to my attic, which is one potential problem. I also had new eavestroughs installed a while ago that apparently slopes to the north to drain, while my house slants to the south, so in fact the eavestrough is level and water doesn’t drain from that area.

Both of these events occurred a number of years ago, but with last winter’s heavy snowfall, which I failed to remove from the roof, disaster struck. I dithered all last summer wondering if I should call a roofer or an insulation person or who to fix the problem. I appreciate any advice you can offer!

— Susan, e-mail

ANSWER — Water leakage into a building may happen at any time of the year, but is often most prevalent when the cold winter weather turns mild, as has happened recently. I will try to provide an explanation of the main probable cause for the source of the leaks in your home.

We must be careful not to confuse one symptom of the malady affecting your home with the cause. The ice dams may be the source of the moisture leaking into your kitchen, but they are not the root cause. Also, the poor slope of the eavestroughs may cause some difficulties in the warm seasons but will make little difference when filled with winter ice. Proper roof repairs may also help prevent leakage of water from melting ice dams but will not be a complete solution unless the interior problems are dealt with, also. That is probably why your recent roofing upgrades have not made the problems disappear.

The problem originates in the design of your older home, but may occur in newer ones, as well. One-and-a half-storey homes typically have several small attics, often three or four, which may create a challenge when it comes to proper insulation and ventilation. This is often compounded by a steep pitched roof and dormers that interrupt the normal flow of air through the attics. What likely is occurring is air and heat loss through these lower, knee-wall attics, and the sloped sections of the ceiling in the upper floor of the home.

When warm air leaks into these areas, because they are not adequately air-sealed, it will cause the winter snow to melt on the roof. This melted snow will freeze as it runs down to the cold eaves, especially at night, creating the ice dams. This may occur for many days or weeks, often leading to long, dangerous icicles overhanging the eaves.

While the remedial work on your home may not be practical until the weather warms, there may be one action that can help in the meantime. Clearing the roof of excess snow may make a difference in the rate of seepage. If there is little snow for the warmer weather and sun to melt, there is less chance of major leakage.

However, the real solution to your problem is to fix the main cause of the ice dams, which will subsequently prevent the melted ice from leaking into your home.

To accomplish this, you must gain access to these problem knee-wall areas, if none already exist, and to air-seal, insulate and ventilate them. The short knee-walls and floor joists inside these attic areas will have to be insulated and some form of air-vapour barrier installed. If insulation is installed between the rafters on the sloped ceilings in the knee-wall attics it must be removed to prevent trapping moisture and condensation from warm air leakage. Once complete, a combination of roof and gable vents may be required to finish the job.

There are two main methods to complete the job mentioned above. Both will help prevent the ice damming, but your choice will depend on several factors. The design of your home, the degree of moisture damage already experienced, the access to the knee-wall areas, and budget restrictions must all be taken into account.

If these areas are already cold attic spaces with decent-sized access hatches and room to work, the conventional method may be sufficient. This is done by installation of polyethylene sheathing for an air-vapour barrier and conventional insulation similar to the walls and attic in any modern home. If the areas have limited access and room for ventilation then spray-in-place foam insulation will be a better solution. The second method could also be applied to almost any situation, but will often be more costly to properly complete.

For the main repair, you should be careful that the contractor hired has extensive knowledge of modern air-sealing techniques. This may be an insulation contractor, roofing contractor, building envelope specialist or general contractor. Ask lots of questions about the contractor’s training and knowledge of air leakage and building envelope issues.

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