EL SEGUNDO, Calif., Nov. 30, 2010 – Weather has been particularly harsh this year throughout much of the United States and Canada. With this brutal winter weather comes a relatively poorly understood roofing problem that can end up costing thousands of dollars in roof repairs: ice dams. The problem usually occurs between January and early March when snow and several days of freezing temperatures combine to create the conditions that allow for ice build-up, and then rapid thawing. Tell-tale signs of the dreaded ice dam have popped up all over the U.S. and Canada during the past few months—icicles hanging from the gutters, ice buildup at the eaves or, even worse, water leakage in the attic, ceilings or walls.
How Ice Dams Form
Roof snow melts through a combination of direct sunlight on the roof, as well as from heat loss through the roof of the building. Normally, snow melts at a rate that allows the snow and ice to run off of the roof, and drainage occurs without incident. However, at the eaves of the roof, less heat is present to melt snow and ice. Ice dams can form when snow on the roof melts and re-freezes in the gutters. Behind the dam, water freezes and thaws, expanding and contracting. This action forces roofing materials apart, traps melted water and allows it to run up under the shingles and then through the roof sheathing, often causing serious damage.
Even with insurance, this can be costly for the homeowner, as most homeowner insurance policies don't cover ice dam removal or roof replacement – unless the homeowner can prove that the ice damaged the roof. Typically, shingle warranties also do not protect against ice dams.
A professional weatherization contractor is specially trained to work under dangerous, icy conditions and is knowledgeable about heat transfer problems. They may be listed under Energy Management and Conservation Consultants or Insulation Contractors in the Yellow Pages.
This is a job for a professional; should you choose to handle it yourself:
- Do not attempt to chip away at the ice dam, as rakes and axes may damage the roof shingles that are especially brittle and prone to breakage when cold.
- Salt or chemicals are corrosive and may shorten the life of metal gutters and downspouts.
Once the ice dam has drained, it is important to keep the gutters clean and the roof cool. The two key ways are:
- Improve the insulation in your attic: Houses in the northern United States and Canada should be equipped with insulation (between the attic floor and interior ceiling) with a heat transfer value of at least R-38 (i.e., that's about 12 inches of fiberglass batts or blown-in cellulose). Insulation should be continuous and airtight across the ceiling so that no warm, moist air can flow from the house into the attic space. Spray polyurethane foam insulation is an especially effective insulator, as it has a very high R-value, is waterproof and forms an airtight seal around electrical conduit, pipes, vents, hatch doors and lighting fixtures. This has the added benefit of lowering your energy bills!
- Ventilation: As a rule of thumb, there should be one square foot of vent for every 150 feet of attic floor area. Added gable or ridge vents help to allow heat and moisture to escape the attic effectively, and reduce the chance of ice dams forming.
The only way to completely eliminate leakage due to ice dams is to modify or replace your roof with a properly installed, high-quality roof that includes an eave protection membrane or a continuous ice-and-water barrier. Eave protection membranes are self-adhered materials that are installed on the roof at the eaves, extend 36-44" up the roof and reside under the shingles. These membranes are self-sealing, continuous barriers, that offer a second layer of protection in case an ice dam forms and water leaks under the shingle. They are commonly available and add only a small amount of incremental cost to a new roof. An even more effective and foolproof technology is a continuous, self-adhered ice-and-water barrier. These materials replace traditional roofing felt underneath the shingles on the roof. They fully adhere to the roof and create a plastic-lined, self-sealed, continuous water barrier that provides a strong secondary layer of protection underneath the shingles that covers the entire roof. In tight economic times, it may be tempting to cut corners, but the risks are not worth it, as Pennsylvania homeowner Camille Dager can attest:
“We installed our roof to save money. This winter, after a heavy snow, an ice dam caused extensive water damage in the ceilings and walls throughout our home. We had to relocate for more than a month while contractors repaired thousands of dollars worth of damage.”
Today, many state codes now require that shingled roofs include an ice-and-water barrier underlayment that extends from the eaves to three feet above the exterior wall of the home (typically two rows) to provide secondary waterproofing protection to shingles and to help prevent future ice damage.
Pete Friedli, director of product management, Henry Company, notes that, "Water and ice barriers, such as Henry's Eaveguard® Self-Adhered Shingle Underlayment and Blueskin® Roof Ice & Water Barrier, provide a highly effective extra layer of protection against wind-driven rain and ice water. Every homeowner should make sure their roofer is using some sort of eave protection or ice and water barrier when they have their roof repaired or replaced."
Eaveguard® underlayment features a sanded, slip-resistant upper surface for worker safety and is engineered for easy application with a split-release film release liner. Standard roofing felt is applied, working up the roof, before shingles are applied. For the best protection, Henry's Blueskin Roof® Ice & Water Barrier™ can be applied from the eave to the ridge.
For more information on Eaveguard Underlayment, spray polyurethane insulation and other roofing solutions, visit www.henry.com or call 800-486-1278.