03/04/2021
Omaha, being an often snowy, cold winter climate, ice dams and icicles are a frequent sight.
Ice dams are a mass of ice that gathers along the lower edge of a roofline where it overhangs the edge of the dwelling.
They are an interesting phenomenon. Often weighing hundreds of pounds an ice dam can compromise the structure of the roof eaves. More importantly they can cause serious damage to your roof, gutters, paint, insulation and interior drywall.
Not every house or even very few in a neighborhood may have them raising serious questions for the homeowner. The answer is usually found in your attic.
Ice dams begin when snow melts on an upper, warmer part of a roof, then flows down to the colder eave overhang, where it refreezes. As the ice accumulates, it forms a blockage that prevents additional snowmelt from flowing off the roof. The ice now begins to back up under the roof shingles, where it melts again, soaking the roof sheathing and leaking into the attic. There, it soaks the insulation (rendering it much less effective). It may now or can leak through to the ceiling drywall below and into your living space.
Ice dams are formed only when the space inside an attic along the underside of the roof deck is above the freezing point. As the warm air beneath the roof heats the shingles and melts the snow on the roof, the water flows down the roofline until it reaches the overhanging eave structure and refreezes. Ice dams usually start or worsen after a heavy snow because of snow's insulating properties. The snow layer traps warm air beneath the snow, which causes it to melt.
Preventing ice dams is a matter of simple thermal physics. If the air in the attic or against the bottom of the roof deck remains cold, it can never melt the snow lying on top of the roof, eliminating the water necessary for ice dams. Preventing ice dams can be done through a combination of:
• Ventilation under the roof deck, which keeps colder outside air circulating through the attic and prevents it from warming above the freezing point so it can melt snow on the roof.
• Insulation in the ceiling below the attic, which will prevent warm air from rising up into the attic space to melt snow on the roof.
• Blocking any heat sources that may be contributing to high temperatures in the attic.
Houses with good attic ventilation generally do not experience ice dams, and the physics are quite simple: By circulating cool outside air in the attic space (or in the rafter spaces just below the roof deck), the roof surface remains below freezing and cannot melt the snow on the roof. Although it's contrary to what many people believe, a cold attic actually means no ice dams, while a warm attic means "homeowner beware."
If you're experiencing the ice dam phenomenon give us a call and we can inspect and make recommendations. Based on our experience these can often be covered under your insurance however we highly suggest you consult your policy or agent for specifics.
These are not generally a roof warranty issue as their source is an attic issue or can be a ventilation issue. An inspection is necessary to determine causation and an appropriate solution.