What is the best way to patch and repair garage wall drywall damaged by moisture in NB?

Moisture-damaged garage drywall in New Brunswick requires complete removal and replacement of affected sections, plus addressing the underlying moisture source before installing new drywall. Simply patching over moisture damage will lead to recurring problems because the Maritime climate's high humidity and temperature swings create ongoing condensation issues in garages.

Assess the Damage and Find the Source

Before any repair work, identify why moisture is reaching your garage walls. In NB's Maritime climate, the most common causes are condensation from bringing snow-covered vehicles into a heated garage, poor ventilation, missing vapour barriers, or water infiltration through foundation cracks or poor exterior grading. Look for water stains, soft or crumbling drywall, mould growth, and musty odours. If the damage extends behind electrical outlets or involves more than a few square feet, shut off power to affected circuits before proceeding.

Check the exterior wall for grading problems — soil should slope away from the garage foundation at least 2% grade (1 inch per foot) for the first 6 feet. Examine the foundation for cracks, especially where frost heaving may have caused movement. Inside the garage, look for condensation patterns on walls and ceiling, particularly during temperature swings when vehicles enter from outside.

Complete Removal and Preparation

Cut out all moisture-damaged drywall at least 6 inches beyond visible damage using a utility knife or drywall saw. Moisture damage often extends further than what's visible on the surface. Remove any wet or compressed insulation behind the drywall — it cannot be salvaged and will continue causing problems if left in place. Allow the wall cavity to dry completely, which may take several days in NB's humid conditions. Use fans and dehumidifiers to accelerate drying.

Treat any mould growth with a solution of 1 part bleach to 10 parts water, wearing proper respiratory protection. If mould covers more than 10 square feet or if you have health concerns, hire a professional remediation company. Check wooden framing for moisture damage — soft, darkened, or spongy wood studs may need reinforcement or replacement by a contractor.

Moisture Prevention Before Repair

Address the root cause before installing new drywall. If condensation is the issue, improve garage ventilation with exhaust fans, passive vents, or simply cracking a window during temperature swings. For attached garages in NB, ensure the vapour barrier (6-mil poly) is intact behind the insulation and properly sealed at all penetrations. Any gaps allow warm, moist air to reach cold exterior sheathing where it condenses.

If water infiltration is the problem, repair foundation cracks with hydraulic cement or polyurethane sealant, improve exterior grading, and ensure gutters and downspouts direct water at least 6 feet from the foundation. In NB's freeze-thaw cycles, small foundation cracks become large ones quickly if not addressed.

Proper Repair Installation

Install new insulation if removed, ensuring it fits snugly without compression. For heated garages or garages attached to living space, install 6-mil poly vapour barrier on the warm (interior) side of the insulation, sealing all joints with acoustical sealant or tuck tape. This step is critical in NB's climate — skipping the vapour barrier leads to recurring condensation problems.

Use moisture-resistant drywall (green board or purple board) for garage repairs, especially in areas prone to condensation. Standard drywall costs $1.50-$2.50 per square foot, while moisture-resistant versions cost $2.00-$3.50 per square foot — the extra cost is worthwhile in NB garages. Cut new drywall to fit the opening, leaving 1/4-inch gaps at edges for expansion. Secure with drywall screws every 8 inches into studs.

Finishing and Future Prevention

Apply mesh tape and joint compound to all seams, feathering edges smooth. Prime with a high-quality moisture-blocking primer before painting — this step is essential in garage environments. Use a semi-gloss or satin paint finish that resists moisture and can be easily cleaned.

Install adequate ventilation if not already present. A simple through-wall exhaust fan ($150-$400 installed) dramatically reduces condensation in heated garages. For attached garages, ensure the fire separation assembly remains intact — any penetrations through the fire-rated wall must be properly sealed with approved fire-stop materials.

When to Hire a Professional

Handle small repairs (under 4 square feet) yourself, but hire professionals for extensive damage, any electrical work around moisture-damaged areas, or situations involving structural framing repairs. If moisture damage recurs despite your repairs, the problem likely involves building envelope issues that require professional diagnosis. Mould remediation covering more than 10 square feet should be handled by certified professionals, especially in attached garages where spores can migrate into living spaces.

Need help finding contractors experienced with moisture issues in NB garages? New Brunswick Garages can match you with professionals who understand Maritime climate challenges and proper moisture management techniques.