When ten million snowflakes per cubic foot fall on your roof, here’s what happens...





Soffit Ventilation

Roof Vent

When it comes to snow load (overload) problems, the  solution is simple:  take the snow off the roof. 

Much more common, however, is “winter only” leaks.  These, usually, are the result of a combination of faults:  inadequate soffit ventilation, roof ventilation, and insulation.  Simply put, if these three things were done perfectly, our attic temperature would always remain almost the same as the outdoor temperature.  Our insulation should keep most of the warm air from our homes in our homes while the warm air from our attics escapes through our vents and cool air is drawn in the soffits.  Modern vent designs and vent locations are such so as to even augment this air flow by catching air flow over the vent/roof ridge and create a venturi effect. 

Having said that, this almost never works perfectly. 

That’s because there are other factors:  temperature fluctuation and solar heating.   These, and any deficiency in the above, conspire to create a warm attic - especially when the day reaches it’s high temperature, and even more so on a sunny day.  Snow, being a reasonably good insulator, helps hold the heat (which is trying to rise) to the roof level.  It melts.  Gravity pulls the water down to the eave (if the shingles are doing what they’re designed to do) where it will freeze since this is the coldest part of the roof’s surface due to the lack of heat from the home, sun, and the fact that the soffits are drawing in cool air from underneath.  As the temperature drops at the end of the day, this problem gets worse:  It creates a dam. 

As the water builds up, it will melt the snow from underneath, but, at the same time the snow cools the water which, at a certain point will freeze.  As this continues, water is trapped against the roof surface by a layer of ice, in effect submersing the shingles which are designed to shed water down with the help of gravity (they maybe could even handle a bit of upward flow from, say, wind) but are not designed to be submersed. 

That leaves our last fault:  inadequate underlayment.  If there is no proper underlayment the water will flood the shingles, reach the wood deck and seep through.


It’s simple- in the summer:  figure any deficiencies in the above and correct them.  In the winter,though, that can be a little tricky.  Often the best solution is to clear the snow and ice until spring. 

Either way, we can help... give us a call.  (613-857-2543)