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Created: Monday April 2nd, 2012 | Last Updated: Friday April 6th, 2012
During the harsh winter months your roof takes more of a beating than you might expect. Especially in the gutters, eaves and valleys. In this article I'll explain ice dams - how they cause roof leaks, how to repair them and how to prevent them.

I've repaired many different roof leaks that have formed from ice dams.  Ice dams are usually formed at the base of your roof where your gutters are located (also known as the eave) see this diagram.  They can also form anywhere else that snow melts and freezes.  Although ice dams can cause water to back up and cause immediate leaks, this is not always the case.  Ice dams can also start leaking after the snow has melted, and still sometimes they won't leak at all.  If you have an ice dam, it's usually not a reason to worry unless it's causing interior damage.  Otherwise I'd recommend leaving it alone.

Understanding ice damming will help you hire a contractor that knows what he's doing when it needs repaired.  If you're feeling confident, you can try to fix the problem yourself, but it may take a while depending on the size of your leak and its location on your roof.  Whatever you do, do not attempt to fix the leak on a snow covered or icy roof – leave that to roofing professionals.

How Ice Dams Occur

Everyone likes icicles in the winter, but they may not be as pleasant as they appear.  If icicles are forming on your gutters, it's a warning sign of a growing or present ice dam.  When snow covers your roof, it's only a matter of time before it melts.  The most common reason for icicles forming is heat escaping from a poorly insulated roof.  When heat escapes, it melts the snow and turns it to water.  As the water runs down your roof it remains warm enough to stay liquid until it reaches a cold spot.  Since your eaves and gutters are uninsulated, they are usually the coldest spot on your roof, and a perfect place for ice to form.  Once your gutters fill with enough ice, they will begin to overflow which causes icicles on one side and a back up (dam) on the other.  The weight of ice in your gutter is generally not an issue, although it can be if your gutters are poorly fastened or contain heavy amounts of ice.  A more common issue develops as the freezing continues – layers of ice backup and form a dam against escaping water.

Shingle roofs are designed to repel water in only 1 direction... down.  Shingles are installed overlapping one another with about 6 inches of each shingle exposed while 6 inches is tucked under the shingle above.  One way ice dams cause leaks is by dammed water working its way back in under shingles and into your home.  If this is the case, the roof will leak while the ice dam is still present.  

Another way ice dams can cause leaks is by extensive ice build up, without any standing water.  If the water that reaches the dam freezes before it can flow back in under the shingles, it can form ice which expands and prys shingles up just enough to creep under them.  As the ice works its way up your roof and lifts the shingles, it will settle underneath of them and not become a problem until it melts.  In this case, you won't notice a leak immediately, but you will when weather warms up.  This can leave a homeowner pretty confused as to where the leak came from since it usually happens well after the snow has melted.

Methods to Fix an Ice Dam Roof Leak

There are several different approaches to fix roof leaks caused by ice dams.  In my experience, the best method for permanently fixing a leak caused by ice dams is by installing Grace Ice and Water ShieldGrace Ice and Water Shield is rolled weather guard specifically designed to add an extra weatherproof layer of protection underneath shingles, siding, windows and other leak-prone areas.  With Grace Ice and Water Shield installed under your shingles, any ice that works its way under the shingles will stay above the layer of Grace Ice and Water Shield when it melts.  This ensures that even though ice dams will be forming, leaks caused by them will be prevented in the future.

Another approach to fixing leaks caused by ice dams is by installing heating cables.  Many businesses use heating cables, but I've also installed them for homeowners.  Heating cables are usually more expensive, and slightly more of a nuisance to install (running electric).  And unfortunately, I have yet to find a brand of heating cable that lasts more than a few years at best.  Most heating cables will short out or stop performing at some point which will require them to be maintained every few years on average.  Many homeowners also do not like the appearence of heating cables on their home, which is another downfall.  Here is a diagram for heat cables.

Even though they aren't the best option, sometimes heating cables are the only option.  On slate roofs, for example, heating cables are a good choice because slate is very brittle and expensive to replace.  You wouldn't want to tear out layers and layers of expensive slate just to install Grace Ice and Water Shield under them.  On the other hand, for a shingle roof you would want to do everything in your power to install Grace Ice and Water Shield underneath before ever considering heating cables.  Grace Ice and Water Shield is much more reliable.

Another way to prevent ice damming is by simply insulating your attic – which is easier said than done.  Many attics are inaccessible where ice dams have formed and therefore this can't be an option.  However, if you do have an open attic without insualtion – definitely insulate it.  This will probably cost a little more than other options but it will pay off in the long run.  Not only will it help to keep the snow on your roof from melting until it is supposed to melt, but it will also save you a noticable amount of money on heating bills throughout the winter. 

Temporary Ice Dam Relief

As a temporary preventative measure you can hire roofers and other construction contractors to manually remove ice dams when they are present.  I've removed ice dam build up from gutters, shoveled off roofs, and even replaced roofing in the winter.  It can be done, but prices are steep.  Especially work that is done on top of an icy roof as opposed to working from a ladder.  Most gutter dams, icicles, and the first foot or two of ice on the eave can be removed from ladder work.  Don't hire a contractor to work on an icy roof unless its absolutely necessary as the price will more than double. 

When manually removing ice dams, roofers will use ice picks, calcium and possibly heat guns.  Removing ice is a long and tedious process that requires hours upon hours of work along with constant care not to damage the roof in the process.  Ice is slowly chiseled away with a hammer and an ice pick, or chisel, and thrown to the ground.  If a contractor opts to use a heat gun, this process will be a little faster, but not much.  Once the ice is at its thinnest, the contractor will spread calcium on the remaining ice.  Calcium is a safe alternative to salt as it will not damage the roof. 

If you are experiencing a leak due to a present ice dam, it may be worth having the ice dam removed manually if cold weather is persisting, however, it will not permanently fix anything.  By spring you will need to have someone permanently fix the problem by using one of the methods above.  Otherwise, you'll have the same problems when cold weather returns.