Commercial building owners and supervisors need to pay attention to snow accumulations on the roof. You should remove the snow from a flat roof because it can create many problems if left where it falls. Of course, the type of roof structures must be taken into account individually, because snow loads and possible damage can vary depending on it. In practice, the recommendation is that when the snow thickness exceeds half a meter, it is mandatory to remove the excess snow from the roof.

A building may suffer these negative effects if snow is not removed:

  • Blocked access to building systems and features
  • Snow and ice may fall off roof edges
  • Damage the drainage system
  • Damage the roofing membranes
  • Heavy loads of snow can cause the roof to collapse.

Here is a list of signs that indicate a building may be too stressed by the snow load. These include:

  • Ceiling problems: A sagging ceiling or sprinkler heads and lines that appear to be lower than usual.
  • Unusual noises: A strained roof may make noises like creaking, popping, and splitting.
  • Roof member problems: Any area of a roof or roof truss that sags should be taken seriously.
  • Drainage problems: Unusual water accumulations on the flat roof could be a clue that this section has sunk. These submerged areas might not be apparent until the snow has melted.
  • Door and window problems: If a door or window cannot be opened or shut, the walls or roof may have moved due to the weight of the snow.
  • Wall problems: Drywall, masonry, and other wall components are susceptible to cracking when a roof is overloaded.

Here at City Service Engineering our staff inspects customers’ roofs, and equipment on it once a month or after a heavy blizzard, and also measures the actual thickness of the snow and the loads caused by it. It is important to note that fresh, thawed wet snow has different densities and mass. Average snow density is +- 250-280 kg/m2, the one that just fell out 150 kg/m2, during thawing 320-380 kg/m2. In our region, on average, roofs can withstand 122 – 160 kg/m2. Cleaning of the roof is scheduled when it is determined that the critical limit is getting close.