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PFebruary 3, 2014

Winter Weather Advisory: Is Your Building Prepared?

As a Delaware Valley leader in Construction Management, we are often asked how our ability to plan, build and operate a facility can guide clients to prevent disasters.  There is no better place to start than with snow.

When serious winter weather is imminent, it is important to understand the possible disastrous effect that snow and ice can have on your building structure. Your building has likely been designed to address the added snow load, however, only recently has the building code has become more stringent.  Moreover, the most overlooked condition is often when building additions and other structures that have been constructed adjacent to your own structure (within 20 feet) create an unintentional drift or snow load. As planners, builders and operators of buildings as well as construction managers, we advise our facility clients to err on the side of being proactive.

How Much Snow Can Your Building Handle?
Delaware, New Jersey, Maryland and Pennsylvania have a mix of code mandated requirements.  In New Castle County, building codes require 25 pounds per square foot (psf) snow load calculated into the design of the structure. Kent County requires 25 psf and Sussex County requires 20 psf. In Pennsylvania, Delaware and most of Chester Counties are within the 25 psf snow load area of the building code map with the northwestern portion of Chester County in the 30 psf range. New Jersey and Maryland building codes specify a range of design snow loads from 20 to 30 psf depending on the local jurisdiction requirements. Heavy snows and repeated snow storms can create packed snow and ice such that only a few feet of depth may weigh 50 psf or more, imposing excessive loads on building structures.

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Snow build up on the roof of Dansko.

What Can You Do to Prevent Losses?

  • Inspect your roofs and make sure roof drains and scuppers are clear prior to an impending winter storm.
  • Most snow related losses occur at stepped elevations where blowing snow tends to drift. Become aware of buildup in these areas.
  • Look for warning signs such as deflection in bar joists or purlins; popping ceiling tile in acoustical ceilings or unusual noises.
  • If any of these situations occur or if you have any questions before or after this winter storm please contact our 24 hour emergency number 302-995-5565 and advise the operator that you have a roof snow load emergency. Someone will immediately contact you from EDiS.

Equivalent-Snow-Load-TableHow Do You Know How Heavy the Snow and Ice on Your Roof is?

Collecting samples of snow/ice is the only practical and accurate way to determine the roof load. The first step is to collect a uniform vertical column of snow from the snow surface to the roof surface. This can be done by thrusting a 3-pound coffee can (6 inches in diameter) repeatedly into the snow until reaching the roof. Empty the snow into a bucket each time the coffee can is filled. After the snow is collected, it is melted and poured back into the coffee can and the depth of the water is measured in inches. This depth multiplied by 5.2 provides the snow load in pounds per square foot. For example, if your melted sample
measures 4 inches deep, your roof snow load is approximately 21 lbs. per square foot (4 x 5.2 = 20.8).

You can also use the table (left) for a quick reference.

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