Municipality Urges Building Owners and Managers to Monitor Roof Loads
Contact: Sharen Walsh, Building Officia
ANCHORAGE- In the last few weeks several roofs in Anchorage have failed due to stress from snow. The buildings involved were generally older (pre-1980) with flat roofs. Several, but not all, failed where snow had drifted.
Newly fallen snow is not very dense. However, over the course of the winter accumulated snow on roofs becomes denser. Per current code the design snow load in Anchorage is 40 pounds per square foot (psf), which is equivalent to approximately two feet of dense snow. A roof designed to current code should not have problems until the load is significantly higher than 40 psf.
It is recommended that building owners and managers monitor the snow loads on their roofs. Of special concern are older buildings with flat roofs, and those with areas of snow drifting, such as at parapets and lower roofs. Special attention should also be paid to long overhangs where snow blankets are draping over the roof edge.
If one hears creaking in the roof, observes excess deflection in trusses or beams, or sees bowing of columns, immediate investigation by a structural engineer is warranted.
Conditions on roofs may worsen as additional snow falls in March and April, building owners should consider preventative roof shoveling. Shoveling a roof is inherently dangerous, so special precautions should be taken. The intent is to lighten the roof load by removing a significant portion of the snow, not necessarily all of it. Trying to remove all of the snow down to the roofing could increase the danger of a shoveler sliding off the roof as well as causing damage to the roofing materials.
If possible, building owners and managers should hire a licensed, bonded roofing or general contractor to do the shoveling.
If you would like further information or would like to talk to an engineer at Building Safety, call 343-8211 and choose option 4, building code questions.