If ice dams start building up regularly on your roof despite your best efforts, this can be caused by a few different issues. The usual causes are usually related to temperature management on your roof or in your attic, but your gutters can also contribute to the issue if they are clogged.
Poor Ventilation
Attic ventilation is vital for a roof's ability to function properly. Without adequate ventilation, hot air can accumulate and become trapped in your attic instead of filtering out. When this heat stays in your attic, the ambient temperature can melt any snow and ice on your roof. Importantly, if the snow and ice near your eaves don't melt—which will usually be the case since your eaves are not above your attic—the water will start to pool up on your roof.
This effect can be exacerbated if you have ducts for your furnace running through your attic and adding to the heat already accumulated there. A roofing professional will need to make modifications to your ventilation system, which can sometimes include fans if necessary to ensure proper airflow.
Poor Insulation
Another possible cause is your insulation. When your roof is properly insulated, it will be protected against some ambient heat from the inside of your house. When even a little insulation starts to fail, this protective barrier can become less effective and allow some heat to pass through.
This can happen when insulation gets old and starts to fall away from your roof, but it can also happen when it gets damaged. Ice dams can sometimes be a problem that builds on itself; as water leaks into your attic, it can damage insulation, making it less effective.
If you check your attic and the ambient temperature isn't very high, your problem may be with your insulation. It's a good idea to ask a professional to inspect it for you, especially if you have an older roof that hasn't been inspected for several years.
Clogged Gutters
Dirty gutters can cause similar problems if they get too clogged. Dirty gutters can be worse than no gutters at all, as they can cause water to back up onto your roof. Once this water becomes stagnant, it's easier for it to penetrate your roof and also for it to freeze and create an ice dam itself. Beyond that, clogged gutters can also get very heavy from holding so much water, and they can start to fall away from your roof and cause damage to its eaves.
Gutters should be inspected and cleaned about once a year, especially if you have many trees in your area or if your area gets heavy winds that can carry debris onto your roof. Gutters aren't the most common cause of recurring ice dams, but if the rest of your roof seems to be in good shape, double-check to make sure there are no clogs and that your gutters are still draining water the way they should.
When you have something you like inside a jar, you probably put a lid on it — right? In a way, you can think of your house in the same manner. You like and value the items inside, along with the inside of the house itself. So, it only makes sense that you would protect the interior of your home with a lid. That lid is your roof.
Keep that perspective in mind as you read this blog. Learning more about roofing will feel more interesting if you remember what a roof does: it protects the inside of the home and the people who live in it.