What Causes Ice Dams in Gutters?

Example of ice dams in gutters

When you are young, icicles are a delight to behold. Sadly, once you’re a homeowner, they should probably be a cause for concern. While small icicles aren’t an issue, large icicle formations are actually a sign of ice dams. But what causes ice dams in gutters, and how do you prevent them in the first place?

What are Ice Dams?

According to the University of Minnesota, “An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof.” Snow falls onto your roof. Some of the snow melts and the water trickles down into the gutters. The water then freezes and piles up, creating a backed-up gutter system full of ice and overflowing with icicles.

What Causes Ice Dams in Gutters?

Ice dams form when the temperature inside the attic is warmer than the temperature outside. The layer of snow closest to the roof grows warm and melts. As the water moves toward the roof’s edge and into the gutters, it cools down and freezes. This freeze-thaw cycle continues until an ice dam forms.

There are three potential causes for ice dams: clogged gutters, insufficient attic insulation, and poor attic ventilation.

ice dams in gutters: ice dam graphic

  1. Clogged Gutters. While not the primary cause, clogged gutters are a big contributing factor to ice dams. If your gutters are already filled with debris, it makes it harder for the water to escape. Instead, the water will sit in your gutters and freeze.
  2. Insufficient Attic Insulation. Since heat rises, it’s important to have a well-insulated attic to keep the heat inside your house from entering the attic space. Believe it or not, a freezing attic is actually a good thing!
  3. Poor Attic Ventilation. Did you know that many roofing companies install ridge vents when they should install an attic fan, or vice versa? In some instances, roofing companies will even install both instead of one or the other! Attic spaces (unless they are spray foam), need to have a perfect combination of air intake and exhaust. The ideal setup is to have a home with soffit vents and a ridge vent. However, if you have a hip & ridge roof, you may instead need an attic fan and not a ridge vent. When you have too much intake or too much exhaust (e.g. an attic fan and a ridge vent) the system can start to work against itself and develop issues like high humidity levels or warmer temperatures.

Should I Worry About Ice Dams?

Ice dams are not going to immediately destroy your home–especially in Raleigh, North Carolina where snowfalls are few and far between. However, ice dams do have the capacity to damage your gutters, roof, insulation, and exterior carpentry. The damage is slow and gradual depending on the size and frequency of the ice dams as well as how long the ice dams take to melt.

Gutter Damage

When the water accumulates and freezes inside your gutter system, it naturally expands. This can consequently bend and damage your gutters. It can also create leaks in your gutters as water slowly melts and finds its way through new openings created by the ice expansion.

Roof Damage

As the ice dams grow, the freezing water will build up and go under the shingles along the roof edge. Since the water melts and freezes bit-by-bit, it can start to find its way under shingles, through your sheathing, and into your home. This freeze-thaw cycle can eventually damage your shingles and roof sheathing while simultaneously causing a roof leak. Note: while ice dams are most common in your gutter system, areas of frozen ice can form on other parts of your roof where water frequently gathers & travels. This includes roof valleys.

Carpentry Damage

Finally, just like the water can creep up and under the shingles, it can also travel behind your gutters and onto the fascia. As the ice slowly melts, it can contribute to wood rot on your fascia, soffits, and even your siding.

How to Prevent Ice Dams in Gutters

So we know that ice dams are bad (of course) and that they can damage your home. So how do we prevent them? There are a few key ways to prevent ice dam formation.

  1. Keep your gutters clean. As we discussed earlier, clogged gutters do not cause ice dams, but they do exacerbate them.
  2. Check your attic ventilation. Have a roofing expert and ask them to inspect your attic ventilation system & offer recommendations.
  3. Improve your attic insulation. Make sure your attic insulation isn’t old, worn down, or inadequate. Have an insulation contractor inspect your attic insulation & check for any heat leaks.

Prevention is key. While there are ways to remove ice dams, they are often dangerous, not very effective, or potentially damaging to your roof and gutters. If it’s an emergency, you can call a local contractor for ice dam removal. Otherwise, sit tight, wait for it to melt, and then take preventative action. Since the Carolinas are a fairly temperate climate, the ice dams shouldn’t last too long before melting.

Questions about ice dams? Let us know in the comments! Need a gutter cleaning? Tired of cleaning your gutters and ready to upgrade to gutter guards? Click here for a free estimate.