Lots of snow melting at higher elevations this week. The attached photo was taken from a home inspection in West Vancouver. You can see the overflow discharge off a flat roof. Typically flat roofs are installed with emergency overflows at 3 to 4 inches above the roof surface. Guess what? There is at least 3 inches of ice water ponding on this roof. Nice feature if that's what you had planned. Otherwise, it's a flashing red light, signaling to the homeowner that the roof drains are not working because they are plugged with debris or frozen over or both. Attention is required once the temperature drops below freezing. Do not attempt to clear the drains in freezing weather as this can damage the roof membrane... with one exception. In case of visible water damage to the interior ceilings, immediate attention is required regardless of temperature. In this particular case the owner was fortunate to have no leaks.