Do I need a ridge vent on my garage roof in New Brunswick?

Whether your NB garage needs a ridge vent depends primarily on whether the garage is insulated, heated, or has a finished ceiling — if any of these apply, then yes, a ridge vent paired with soffit vents is strongly recommended and often required by code. For a simple uninsulated, unheated detached garage with open rafters, a ridge vent is not strictly necessary, but it still provides meaningful benefits in NB's climate.

The purpose of roof ventilation is to allow air circulation through the attic or rafter space, which serves two critical functions in New Brunswick. First, it removes moisture that would otherwise condense on the underside of the roof sheathing during cold weather, leading to rot, mould, and premature sheathing failure. Second, it equalizes the temperature across the roof surface, which helps prevent ice dams — one of the most common and damaging roofing problems in NB's climate. When warm air from a heated or insulated garage rises and heats the upper portion of the roof, snow melts and refreezes at the cold eave edge, creating ice dams that force water under the shingles. Proper ridge-and-soffit ventilation keeps the entire roof deck cold, preventing this melt-refreeze cycle.

For insulated or heated garages, the NB Building Code requires a minimum ventilation ratio of 1:300 (one square foot of net free ventilation area for every 300 square feet of insulated ceiling area), with the ventilation split roughly 50/50 between intake at the soffits and exhaust at the ridge. A continuous ridge vent paired with continuous perforated soffit panels is the most effective and balanced way to achieve this airflow. For a typical 24x24 two-car garage, that works out to approximately 2 square feet of total net free ventilation area — about 1 square foot at the soffits and 1 square foot at the ridge. Most continuous ridge vent products provide 18 square inches of net free area per linear foot, so a 24-foot ridge vent provides ample exhaust capacity.

For uninsulated, unheated garages, ventilation is less critical from a code standpoint, but NB's Maritime humidity still creates condensation issues even in unheated spaces. During spring and fall when daytime temperatures warm the garage interior and nighttime temperatures drop below the dew point, moisture condenses on metal tools, vehicles, and the underside of the roof sheathing. A ridge vent and soffit vents create passive airflow that carries this moisture out, extending the life of the roof sheathing and reducing rust and mildew on garage contents. The cost of adding a ridge vent during a new garage build or re-roof is only $200 to $500 in materials and labour — a modest investment for meaningful moisture protection.

If your garage has a bonus room or loft space above, proper ventilation becomes absolutely essential. The ceiling of the living space must be insulated, and the space between the top of the insulation and the underside of the roof sheathing must be ventilated from soffit to ridge. Baffles (also called rafter vents or chutes) should be installed in every rafter bay to maintain a clear air channel from the soffit intake to the ridge exhaust. Without this continuous airflow, moisture accumulates in the roof assembly, leading to sheathing rot and potential mould problems that are expensive to remediate — typically $3,000 to $8,000 to replace damaged sheathing and correct the ventilation on an existing garage.

A common mistake on NB garages is installing a ridge vent without adequate soffit intake, or blocking the soffit vents with insulation pushed too tightly against the roof sheathing. The ridge vent can only exhaust air if there is a clear path for replacement air to enter at the soffits. Every soffit bay should have either continuous perforated soffit panels or individual soffit vents, and if the garage is insulated, baffles must keep the insulation from blocking the airflow path.

Ridge vent installation is straightforward during a new build or re-roof — the roofer cuts a narrow slot along the ridge and caps it with the vent product, which is then shingled over for a clean appearance. Retrofitting a ridge vent on an existing garage is also possible but should be done by a professional roofer who can cut the slot accurately without damaging the ridge board or trusses. If you are building or re-roofing a garage in New Brunswick, New Brunswick Garages can connect you with local roofing contractors who understand NB's ventilation requirements.