Managing Winter Condensation & Mould in Your Garage
Garage Door Condensation Solutions — How to Prevent Mould and Improve Weather Sealing
If your garage smells musty in winter, has water pooling on the floor, or has dark patches appearing on the walls and ceiling, you're dealing with condensation. It's one of the most common garage problems in Australia — and one of the least understood.
The good news is it's manageable. The bad news is there's no single fix. Condensation is a systems problem, and solving it properly means understanding what's causing it first.
Why Garages Condensate
Condensation forms when warm, moist air hits a cold surface. In a garage, the usual culprits are the concrete slab, uninsulated metal walls or roof sheeting, the door itself, and vehicles brought in cold from outside.
The moisture source is typically outdoor air entering through gaps around the door, vehicles dripping rainwater, household activities in attached garages, or rising damp through the slab.
Garage Door Weather Seals — Start Here
A door with gaps at the bottom, sides, or top is continuously exchanging warm inside air with cold outside air. Check your garage door weather seals first — it's the cheapest fix and often the most effective.
The bottom seal gets the most wear. It should make continuous contact with the floor across the full width when closed. If you can see daylight or feel a draught, it needs replacing. Replacement seals are available from most hardware stores — search your door brand and model for the correct profile.
For roller doors, also check where the guides meet the wall. A bead of silicone at that junction closes off a surprising amount of air infiltration. On sectional doors, check the full perimeter seal for cracking or compression.
Insulation — The Cold Surface Problem
Weather seals manage air infiltration. Insulation manages the cold surface itself.
An uninsulated steel door is essentially a large cold radiator in winter. You can ventilate all you like — if the door surface is cold, moisture will deposit on it.
Some doors come insulated from the factory — notably the B&D Neo® and certain sectional models. Retrofit insulation panels are available from hardware suppliers for most sectional door profiles if you're not ready to replace the door. If you are replacing it, specifying an insulated door is worth the modest price difference, particularly in Victoria, Tasmania, or elevated areas of NSW and QLD.
Uninsulated roof sheeting and walls are often just as much to blame as the door. Foil-backed insulation batts are widely available and can be retrofitted reasonably easily into most shed and garage structures.
Ventilation — Letting Moisture Out
Sealing the garage without addressing internal moisture sources just traps humidity. The solution is controlled ventilation — enough to let moisture escape without pulling in more cold air than you remove.
Roof or wall vents positioned high in the space work by convection and cost very little to install. Opening the door for 20–30 minutes after parking a wet vehicle is free and surprisingly effective. For persistent moisture sources, a wall-mounted exhaust fan on a timer or humidity sensor is the next step up.
If Mould Has Already Taken Hold
Controlling condensation stops mould spreading — it doesn't remove what's there. Treat existing mould with a one-part bleach to four-parts water solution, leave 15–20 minutes, scrub and rinse. A mould-resistant sealer on bare concrete or masonry afterwards reduces recurrence. Anti-condensation paint on walls and ceilings provides a complementary layer of protection.
Store items in sealed plastic tubs rather than cardboard — cardboard holds moisture and is ideal mould habitat.
Where to Start
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Check and replace garage door weather seals
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Add passive roof ventilation
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Insulate the door
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Insulate roof and walls
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Add active ventilation if needed
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Treat existing mould and reseal surfaces
Most problems are solved at steps one and two.
Simple solution
Seals first, insulation second, ventilation ongoing. If you're replacing the door anyway, do all three at once — it's the right time to spec it properly.
Browse our full door range if you're considering an upgrade.