Ice Dams and water backup leaks caused by poor roof and building design.


Poor building design is often the cause of ice dams and the resulting roof leaks. Houses are often designed with little to no overhang at the eaves of the house. Without an adequate overhang there is no room to install the needed vents at the soffit. The best soffit ventilation is usually continuous strip vents installed the length of the roof eaves. Small round plug style vents and larger louvered vents cut and installed between roof rafters can work well but are often insufficient.The house pictured below has some overhang but little space to install venting. The overhang is mostly taken up by mouldings and trim work.


The design of the roof, with the large gable valley ending close to a small dormer, also adds to the problem.  This area is a perfect trap for both snow drifts to occur, and for snow from the upper roof areas sliding down and condensing into one small area.


Poor roof design and ice dams


Short soffit area contributing to ice dams

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