Snow

Snow removal tips for rooftop parking

Common de-icing materials and careless snow clearing can cause premature deterioration
Monday, December 9, 2013
By Dale Kerr

Snow and ice removal are important at apartments where exterior parking and driveways are located on the roof of an underground parking garage. Or, alternatively, at condominiums with a separate garage structure with rooftop parking.

Common de-icing materials, like sodium chloride, calcium chloride and potassium chloride, adversely affect concrete. If a leak in the waterproofing allows these materials to reach the reinforcing steel, it will cause corrosion. The rust takes up more volume than the steel, which creates enough stress in the concrete to cause pieces to break off.

While more expensive, selecting de-icing products that do not contain chlorides, like urea fertilizers or calcium magnesium acetate, is recommended. To improve traction and prevent skidding problems, salt can be added to sand at approximately three to six per cent by weight. If sand is being used, drains should be protected from clogging.

Workers should take extreme care when removing snow or ice from exposed parking garages. The operation of snow and ice removal equipment often damages the roof system, most commonly due to dropping or dragging heavy or sharp objects on the surface.

The expansion joints are particularly susceptible to damage. Snowplows should not cross an expansion joint at an angle greater than 75 degrees. If possible, it is best to clear snow parallel to the joint. This approach minimizes the chances that a blade will be caught on the joint and cause damage. Since the expansion joint may be hidden beneath the snow, each end of the joint should be clearly identified by markings on the walls or parapets, or by flags embedded in sand-filled drums.

If possible, workers should also avoid using a steel blade on the plow; rather, a power brush should be used. If a steel blade must be used, damage can be prevented by attaching a heavy rubber cutting edge to the bottom to hold the steel edge at least 12 millimetres (half an inch) above the deck surface.

Garage roofs should not be overloaded by a snowplow or by stockpiling snow. It is best if snow is completely removed from a garage roof, as it can become quite dense and form ice. Overloading can cause cracking, which can then accelerate the deterioration of the garage.

Snow piles should also be placed so that melt water does not flow over drive surfaces, where it could later freeze and create a safety hazard.

Dale D. Kerr, M. Eng., is the chief operating officer of GRG Building Consultants. Kerr is the author of the ACMO Student Manual for Physical Building Maintenance, which covers all aspects of condominium repair and maintenance. She can be reached at 800-838-8183.

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