How do you repair stucco around a dryer vent or exhaust fan opening in Ottawa?

Penetrations through stucco walls — dryer vents, bathroom exhaust fans, range hoods, HRV intakes and exhausts — are some of the most common failure points on Ottawa homes. The combination of warm moist air hitting cold stucco, plus the inherent difficulty of sealing a round or rectangular opening in a textured surface, means these areas need careful attention.

Why These Areas Fail

In Ottawa's winters, warm exhaust air condenses on the cold vent hood and surrounding stucco, creating a constant moisture source. When temperatures drop below freezing (which is roughly November through March), that moisture freezes inside the stucco and gradually breaks it apart. You'll often see a ring of crumbling, discoloured stucco around dryer vents — that's freeze-thaw damage from condensation.

The repair process involves several steps:

• Remove damaged stucco — Chip away all soft, crumbling material around the penetration until you reach solid, well-bonded stucco. This usually extends 3–6 inches beyond the visible damage.- Inspect the flashing and vent boot — The vent should have a proper flashing or mounting plate that sits behind the stucco's weather-resistant barrier (building paper or house wrap). On many older Ottawa homes, the vent was just shoved through a hole with caulk around it — that's the root cause of the failure.- Install proper flashing if missing — A metal or flexible flashing collar integrates with the wall's drainage plane. This is the most important step and the one most DIY repairs skip.- Rebuild the stucco — New metal lath is tied into the existing lath, and stucco is applied in layers (scratch, brown, finish) right up to the vent flange. The stucco should lap slightly over the flashing but not block drainage.- Seal the perimeter — A bead of high-quality polyurethane or silicone sealant goes between the vent hood and the finished stucco. Use a sealant rated for exterior temperatures down to at least -40°C.

Important Ottawa-specific details:

• Dryer vents should have a proper louvered or magnetic damper to prevent cold air backdraft — Ottawa's wind chill can push frigid air straight into your laundry room- HRV intakes and exhausts need particular care because they run continuously, creating constant condensation potential at the wall penetration- Make sure the vent hood extends far enough from the wall (at least 2 inches) so that exhaust moisture doesn't run back along the stucco surface

A single vent repair typically costs $250–$500 in Ottawa if the flashing is intact, or $400–$800 if the flashing needs to be replaced or installed for the first time. If you have multiple vents showing damage, most contractors will offer a better per-unit rate to address them all at once.

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Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• Justyn Rook Contracting
• RenoMotion Inc.
• Home Front Services
• Regimbal
• The Fixer

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