Vail Daily column: Be mindful of snow on roofs
Special to the Daily
Vail, CO Colorado
According to the latest snow report, 322 inches of that light, fluffy Colorado powder has fallen on Vail Mountain so far this season. That sounds like a huge amount of snow until it’s compacted and groomed on the ski runs into smooth corduroy for the enjoyment of all. The end result is about 5.5 feet of good base, perfect for lasting the entire season and carving those big, smooth turns that put a smile on your face in spite of the cold.
The point is, when snow gets compacted, it becomes denser and a lot heavier. But using a machine isn’t the only way for snow to become compacted. It will naturally settle over time by itself into a heavy layer. And that snowpack will greatly increase the load on a roof. So a roof with only a couple of feet of snow on it could struggle to support that load.
Roof systems are designed with many factors in mind, including the pitch, roof material, installation of snow fences and elevation of the home, just to name a few. As an example, in Eagle County, a home at an elevation of 7,500 feet should have a roof design capable of holding a snow load of approximately 61 pounds per square foot. In Vail, that number increases to approximately 100 pounds per square foot. However, some of the older roofs in Vail were designed with only about 55 pounds of snow load per square foot. That makes it even more important to monitor the snow loads.
Without this becoming a lengthy and boring article full of equations and formulas, let’s just say as the ice dams and snow accumulates, the structural integrity of a roof could become overloaded, causing undo stress on the structural members. Remember the video of the roof collapsing at the Metrodome in Minneapolis this past winter? That occurred after only 20 inches of snow fell.
There are other considerations when snow is allowed to accumulate on a roof. If allowed to build up high enough, it can block roof vents, causing a backup of sewer gases creating obnoxious smells, or worse, deadly carbon monoxide build-up in the house.
And as long as the subject of ice dams came up, keep an eye on them as they build up. An ice dam forms as snow melts off the roof running down underneath the snow until it reaches the colder portion of the eaves, where it refreezes. As the ice builds up, it traps the water running off behind the dam, forming a pool behind the eaves. As the pool grows, the water will seek the lowest point, usually finding a spot between the seams of the roof and drip into the home. That can cause dry rot, mold, drywall damage and staining of any wood trim inside the house.
Ice dams and icicles can break off in large blocks, sometimes weighing hundreds of pounds. As they fall, they can rip off shingles, gutters, or the fascia on the eaves with them, leaving costly repairs to be made. Those falling blocks can also break unprotected gas meters, dent cars, or worse, injure or kill someone unfortunate enough to be underneath.
If snow and ice does need to be removed from a roof, don’t attempt to do any roof work without the necessary fall protection. Use an approved harness and a securely anchored rope. An unexpected slip or falling block of snow can easily sweep a person off a roof. Also be sure to cordon off the area where the snow will be thrown so no one walks under the “drop zone.”
Of course, when in doubt of the ability to do the job correctly, hire a professional. It will always be cheaper in the long run.
Al Bosworth is a fire engineer for Vail Fire and Emergency Services.
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