How to prevent ice dams and roof leaks

Here we are in the middle of another cold Massachusetts winter and like every winter here in New England many homeowners will have major problems with ice dams causing roof leaks and shingle damage.

Although ice dams may seem like an unstoppable force of nature, they are actually quite preventable. Attics and vaulted or cathedral ceiling areas that have been properly incorporated into the general building envelope have no problem with ice dams and icicles in cold seasons. By using proper insulation and ventilation techniques, ice dams can be stopped dead in their tracks (pun intended).

Here is a typical scenario for ice dam formation:

1. A house has a buildup of snow on the roof.
2. The outside temperature is below zero.
3. The temperature inside the attic is above freezing, which raises the roof temperature above freezing.
4. Due to the warm roof, the snow on top begins to melt from the bottom up.
5. This melted snow water tries to run down and out of the roof.
6. As soon as the water reaches the edge of the roof, it is exposed to the freezing air.
7. Water refreezes as ice instead of snow in gutters, if any, and along roof edges.
8. As more and more meltwater continues to fall through the roof, it continues to freeze behind and on top of the previously frozen runoff, forming an ever-larger ice dam.

So how do ice dams cause roof leaks?

Melted snowwater no longer freezes immediately after the ice dam has begun to take shape. Once the ice dam has built up a bit, it literally creates a dam that traps the rest of the water that tries to escape from the roof behind it. While this trapped water will eventually freeze, it can take a while and during that time a portion of the shingles on this roof, behind the ice dam, are basically submerged in water.

Now, of course, your roof shingles are supposed to protect your home from the weather, namely rain and snow. However, most roofing materials are not meant to have a pond or river on top of it.

So what can you do to prevent ice dams?

First of all, you need to recognize that proper insulation and ventilation is the key (see image to the right). If we’re talking about an attic area, this usually means that the insulation should go up the walls of your house and then over the attic floor joists forming an ideal insulation envelope. In the attic scenario, only the attic floor should be insulated, not the bottom of the roof!

Adequate ventilation is also required. Outside air must be able to enter the attic for the the attic temperature is the same as the outside temperature. This ventilation is accomplished through the use of gable vents, soffit vents, and a roof ridge vent.

On roof systems with attic areas below them, it’s fairly easy to have a contractor who knows what he’s doing to correct any issues with proper insulation and ventilation. However, ceiling systems with a cathedral ceiling below them that have these issues are much more of a project to correct, but they can be corrected.

In order to have a properly ventilated and insulated cathedral ceiling, the contractor must install baffles inside each bay prior to installing the insulation. These baffles allow air to flow between the soffit vents and the ridge vent, keeping the underside of the roof at the same temperature as the outside. If these baffles are not installed in your cathedral ceiling, then the contractor will need to remove the existing drywall and insulation from your ceiling to properly ventilate the area. This type of project will be more expensive than an attic project.

In addition to the ice dam problem, if your attic is warmer than the outside temperature, you’re also wasting a lot of money heating that space. So basically you are paying extra money on your heating bill for the privilege of making huge ice dams and icicles that cause roof leaks and destroy your roof. It makes it even worse when you think about it that way, doesn’t it?

What can be done with existing ice dams?

If it’s the middle of winter and you have ice clumps or, from past experience, you think they will form soon, there are a few steps you can take. First of all, if you don’t have experience climbing a roof in winter, especially snow, don’t do it! Call a professional. What you can do is go to your local hardware store and buy a snow rake that has an extendable handle designed to remove snow from the first few feet of the roof and try to remove some of that snow from the ground before it falls. has a chance of melting and freezing along the edges of the roof. You can also do this once the ice dam has formed and keep it from growing any further and give it a chance to melt, hopefully.

Additionally, many roofing contractors, including us, work through the winter and often provide roof snow removal services in addition to your typical roofing services. This is a service that we are happy to provide to our customers here in Massachusetts, for example. Again, don’t try to do this yourself. Between icy stairs and slippery roofs, it’s a recipe for disaster for the inexperienced.

There are also some products on the market that can help prevent ice dams before they form and melt ice dams if they have already formed. You should be able to find a home improvement store in your area that sells a product that is basically a heated, sheathed wire that you clamp along the edges of the roof, then plug it in when conditions are right for levees to form. of ice (see image to the right). These actually work quite well, however they are not solving the real problem which of course is ventilation and insulation issues. However, they may be suitable for some homes in some circumstances.

Most home improvement and hardware stores also sell pellets or tablets that are designed to be dropped from the ground onto the ceiling. These tablets will supposedly melt the ice on the roof as they dissolve in the water that runs across the roof towards the ice dam. I have no experience with these products, so I can’t say for sure if they work as designed or not. However, some people say that they have worked for their ice dam problems. A couple of things I would be concerned about as a roofing contractor are possible damage to shingles from the chemicals these tablets are made of (salt is not good for asphalt shingles), as well as staining the roof. with those same chemicals. And even in a base case situation, this product is still just a band-aid for a bigger problem.

Roofing techniques suitable for cold climates

In addition to making sure the roof has proper ventilation and attic insulation, there is an added level of security against roof leaking and ice dam issues that all responsible and ethical roofing contractors should take cold weather concerns with. regarding sloped roofs with asphalt shingles. . When a new roof is installed these days, an extra layer of protection called an ice and water membrane must be installed from the edge to at least 3 feet above the roof.

This added layer of protection will help prevent leaks if ice dams form along the edges of the roof. The Ice and Water Membrane will not prevent ice dams, it is simply added security to help protect the plywood sheathing under your asphalt shingles and prevent leaks in the event of ice dams.