It’s 20 below, why is my roof leaking? Its freezing cold out, there’s a foot of snow everywhere and it hasn’t rained in months, yet your roof is leaking and your drywall ceiling is dripping water. There are several reasons why your roof is leaking or a culmination of two or more.

Ice Dams Contrary to popular belief amongst homeowners, roof shingles do not waterproof your roof. They in fact shed water in a downward overlapping fashion. When an ice dam forms it is the result of an underlying problem in your attic space and since ice melts slower than snow, any snow meltwater is contained by and pools behind the ice dam. The contained water as it pools, moves uphill underneath the shingles and the resulting leak occurs. Ice dams form when the attic space air is warmer than the outside air. The snow thus melts at the roof level underneath the snow pack. Where the roof extends past the homes inside wall, this is called the soffit. This is the cold or unheated area of roofing and when the meltwater passes the homes inside wall to the colder soffit and eaves area, it freezes. It will continue to build upon itself and to grow in size, often creeping up underneath the shingles. Other factors that cause roof leaks in winter are condensation issues such as air leaks around skylights, uninsulated bathroom or clothes dryer exhaust pipes, broken positive ventilation plumbing pipes compromised or broken furnace or hot water exhaust vents, poorly insulated attics and poor or improper attic ventilation.

Skylights typically last 15 -22 years depending on the quality (glass or plastic) and the installation. As they are exposed to constant UV light, over time the skylight seals begin to dry and crack which cause air leakage and often water leakage. When the seals are compromised the warmer rising air inside your home meets the leaking colder air in winter time and causes  condensation leaks. Discolouration of the ceiling around the skylight or water droplets on the inside of the glass are good indicators its time to replace them. At Tops Roofing Company, we recommend skylights be replaced each time you reface the roof shingles, if not before.

Bathroom Fan Vents and dryer vents are quite often the main culprits in winter roof leaks and it always comes down to the installation. Ducting from fans or dryers carries very warm moist air and must be insulated within the attic space to prevent condensation leaks in winter. Further, ducting, whether flexible or rigid type galvanized pipe, must vent vertically. There can be no horizontal lay in the ducting. Horizontal lay will cause vented air to remain in the ducting after the fan is shut off, causing mold growth within the ducting and potential water leakage back down and through the vent. Ducting must also breach the plywood roof sheathing and penetrate through to the outside and into the exhaust vent unless a correct vent duct collar is attached and fastened securely with a metal strap clamp.

Bathroom Fan Vents

Plumbing Vent Pipes and furnace or hot water heater vent pipes, though not a common occurrence, may get broken or leak air into the attic space if not correctly installed or are impacted by an outside force. Tree branches, construction or renovation work and a new shingle roof installation are typically the culprits. In summer, the ambient air is warm and thus condensation is not an issue, but as winter arrives and with it very cold air, serious condensation leakage will occur. If you’ve had your home upgraded to high efficiency direct vented HVAC, you should have unnecessary vent pipes removed when you replace your old roof shingles

Broken Plumbing Ventilation Pipe
Broken Plumbing Ventilation Pipe

Attic Insulation compresses over time thus loosing its thermal resistance or R value. It’s a good idea to have the R value of your attic insulation assessed and the insulation topped up if required, every time you replace your roof shingles. Insulation keeps the cool in and the heat out in summer and rise versa in winter. Insufficient attic insulation is a main contributor to ice damming.

Ventilation is key to preventing roof leaks in winter and especially so in the prevention of ice damming. You need to have not only a sufficient number of roof vents or linear ft. of ridge venting but also an equal distribution and the correct placement of vents. Roof vents continually exchange the the air in your attic with fresh outside air. In order to exchange air, roof vents need to be able to draw this outside air in. Air is drawn in through the overhang or soffit area venting, moves through the attic space and back to the outside through the higher up roof or ridge venting. No amount of roof vents will provide efficient air exchange if they cannot draw in fresh air. This is why on low slope roofs especially, it is important to have u shaped air baffles installed on top of the attic insulation and extending into the soffit to create air channels from which roof vents are able to draw from. Most new homes will have continuous vented aluminum soffits, however, older homes will have a covered wood soffit with vent holes into the soffit and vent grills installed over top. As well, this wood soffit is often covered with aluminum to reduce maintenance and eliminate the need to paint the soffits. At Tops Roofing we can assess and correct all your ventilation requirements to ensure smooth and efficient venting in both summer and winter.