Ice dams — or ice buildup on roof eaves — are all too obvious and all too familiar to Minnesota homeowners. Although those sparkling icicles hanging from your St Paul Minnesota home may look pretty, icicles are a signal trouble could be lurking. Once you understand their potential for roof damage, they tend to lose their appeal.

Prevent Ice Dams

The problem with icicles is they can create an ice dam, which prevents water from draining off the house and instead allows it to pool along the roof line and cause wood rot, water-logged ceilings, and soggy insulation. Not to mention, the sheer weight of ice and water can cause your gutters or part of your roof to collapse.

The best way to eliminate prevent ice dams once and for all is to properly insulate your attic, so the roof stays cold and not warm enough to melt fallen snow. If you noticed icicles last winter, it’s probably time to upgrade your insulation and seal up any air leaks (warm air from inside the house seeping into the attic). The improved insulation will also lower your energy bills, and you may qualify for a state or federal energy-efficiency tax credit or rebate.

Prevent Roof Collapse

How much snow is too much for your home’s roof to handle?

Evaluate your risk of roof top snow/ice accumulation

  • Melting snow tends to more quickly run off of steep sloped roofs with slopes greater than 3 in. of slope in 12 in. of horizontal distance, particularly the steeper ones that are typically found on houses in northern climates.
  • Ice and snow tend to more readily accumulate on low slope and flat roofs over porches, lanais or parts of a home that are next to a taller section of the house, especially during high winds.

Estimate how much weight your roof can support

  • Unless the roof structure is damaged or decayed, most residential roofs regardless of the location of the house should be able to support 20 lbs per square foot of snow before they become stressed.
  • In some areas throughout the United States, snow loads used in home design may be considerably higher and the roofs may be able to resist a greater depth of snow.
  • If you live in an area known for lots of snow, you can probably check with your building department to find out if higher loads were used at the time your home was built.

Estimate how much the snow on your roof weighs using these guidelines from IBHS:

Fresh snow: 10-12 in. of new snow is equal to one in. of water, or about 5 lbs per square foot of roof space, so you could have up to 4 ft. of new snow before the roof will become stressed.

Packed snow: 3-5 in. of old snow is equal to one inch of water, or about 5 lbs per square foot of roof space, so anything more than 2 ft. of old snow could be too much for your roof to handle.

Total accumulated weight: two ft. of old snow and two ft. of new snow could weigh as much as 60 lbs per square foot of roof space, which is beyond the typical snow load capacity of most roofs.

Ice: one in. of ice equals one ft. of fresh snow.

Snow removal may be necessary to avoid roof collapse

If you are in the “danger zone” according to chart above or if the loads you estimate based on the thickness of the various types of snow and ice exceed 20-25 psf, you should consider removing snow from your roof.

Many homeowners pull the snow off the eaves using a roof rake or push broom. While this will remove snow, it may also damage your roofing materials. Shingles are particularly vulnerable when they are cold and brittle.

For safe removal that won’t endanger you or damage your roof, use a snow rake with a long extension arm that will allow you to remove the snow while standing on the ground or hire a roof snow removal contractor.

Source: 2012 Insurance Institute for Business & Home Safety