What to Expect from Engineering Reports: Ice Damming

Ice dams are a common occurrence in certain geographic areas.  Because ice dams can be confused with other causes of damage, a methodical, scientific approach should be taken by your engineering expert to determine what caused the problem reported by the building owner.

The location, construction type, age, and other characteristics of the building will be provided in the engineer’s report.  A typical investigation will begin with the building owner pointing out areas of damage, such as water stains inside the building.  The report may provide relevant background from the owner, such as when the owner first observed the problem, especially if the background information is relevant to the conclusions.  Information provided by the owner may be useful later when analyzing weather data in the context of when the problem was observed.  Because the engineer may visit the property long after the roof has cleared of snow and ice, photographs or video from the owner may be useful for analysis.

Observations of any resulting damage that was potentially caused by ice damming, such as water stains on the ceilings, walls, and soffits, and also in the attic, should be documented in the report with photographs.  Moisture readings of stained building materials, such as drywall and roof framing, indicate whether the water intrusion is ongoing or has ceased.  Because ice damming is typically associated with attic ventilation that cannot maintain a consistent temperature of the roof deck, the ventilation should be observed if the attic and/or roof are accessible.  If ventilation pathways are blocked or do not exist, this should be documented.  Depending on the extent of any cover from snow and ice, it may be difficult to access the roof to observe beneath the shingles, but the engineer may attempt to determine whether ice and water barrier underlayment (at least two layers of underlayment cemented together or a self-adhering polymer-modified bitumen sheet) was installed between the roof deck and the shingles along the eaves.  The condition of plumbing boots, skylights, chimneys, and other roof penetrations and flashings should also be observed if possible.

In comprehensive engineering reports, weather data may be researched during the time period of interest.  Using weather data from sources such as the National Weather Service and National Oceanic and Atmospheric Administration, the report will identify the weather conditions that were reported when the loss occurred.  The weather data may summarize the outdoor temperatures, depth of snowfall and snow accumulation, periods of snowmelt, and other relevant environmental factors.

A comprehensive report will also provide an explanation of the nature of ice damming, which can occur when ice and snow melt and refreeze on the roof.  If alternate causes of damage are being considered, such as condensation or isolated roof leaks, applicable research should be provided on these separate phenomena.

The engineering report may address the building codes in effect when the building was constructed or when it was re-roofed.  Depending on when the roof was installed and the geographic location of the property, ice and water barrier underlayment may have been required by the applicable building code.  Depending on the existence and stringency of the local code enforcement agency, the roofing materials installed may have been documented.

With evidence collection and research complete, the report will provide conclusions regarding the origin and cause of any damage found.  The report will discuss the environmental conditions and the physical condition and characteristics of the structure, and how these factors contributed to the observed damage.  Depending on the nature and extent of the damage, it may be possible to conclude whether the damage was a recent occurrence or has been an ongoing problem.  If repair recommendations have been requested, the report will provide a repair protocol.

In numerous cases, we have found that what initially was suspected to be water intrusion from ice damming was actually the result of excessive condensation in the attic.  Signs of excessive condensation include wet and/or frosty roof decking, widespread mold growth, frost and rust on the nail heads throughout the attic, and drip marks on the insulation on the attic floor, which result from the heated air leaking from the building into the attic.  Conversely, ice damming is typically localized and occurs close to the roof’s eaves where the refreezing of melted snow and ice takes place (Figure 1).  Your engineer will also consider other factors such as deterioration at roof penetrations and isolated roof leaks, which may display symptoms similar to ice damming.

Figure 1: Conditions Conducive to Ice Damming


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About the Author

Casey McKinley has over 20 years of engineering experience, and has completed approximately 2,400 forensic investigations. Mr. McKinley has worked in the following industries: civil engineering design, land development, construction management, and as a construction site supervisor. His areas of expertise are roof inspections and stormwater, and his project capabilities include flood studies, hail and wind damage, water intrusion, cladding/window failures, construction defects/code issues, and structural storm damage, among others. Mr. McKinley is a licensed professional engineer in Colorado, Connecticut, Indiana, Kentucky, Massachusetts, Maryland, Michigan, Minnesota, New Jersey, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Virginia, Washington and West Virginia. He earned his Bachelor’s degree in Civil and Environmental Engineering from the University of Cincinnati.

Read Casey McKinley’s full professional profile here.

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