You walk into the garage on a January morning and the inside of the door is beaded with water. Some of it has run down and left a wet line along the floor. It hasn't rained since yesterday, the roof is fine, and the weatherstrip looks intact. What you're looking at is garage door condensation, and Metro Vancouver's long, damp winters give it plenty of chances to show up.
This guide explains why it happens, using the dew point and Environment and Climate Change Canada's climate normals for Vancouver International Airport. It covers how to tell condensation from a real leak and which fixes the door manufacturers' association actually recommends. It also flags one popular fix that can damage the door.
Why garage door condensation happens
Air always holds some water vapour. Warmer air can hold more of it than cold air. When air touches a surface that is colder than its dew point, it can't hold all of that vapour any more, and the extra turns into liquid on the surface. A cold drink "sweats" on a summer patio for the same reason.
A garage door is usually the coldest large surface in the garage. On a plain single-skin steel door, there's only a thin sheet of steel between the garage and the weather, so it sits only a little warmer than the outdoor air. The walls and ceiling are insulated, and the house next door bleeds a bit of heat into the space. So the air inside is warmer and often wetter than the air outside, and the door is where the two meet.
The Door & Access Systems Manufacturers Association (DASMA) puts it plainly in its Technical Data Sheet 195, Garage Doors and Condensation. It says condensation is not normally a product defect, and calls it "characteristic of a warm, humid garage and a cooler garage door surface due to a colder exterior temperature."
Dew point in plain numbers
The table below uses the standard Magnus approximation for dew point. These are our own worked examples, not measurements from any particular garage. Read across: if the inside face of the door is colder than the dew point in the last column, water will form on it.
| Garage air temperature | Relative humidity | Approximate dew point |
|---|---|---|
| 10 °C | 60% | 2.6 °C |
| 10 °C | 80% | 6.7 °C |
| 12 °C | 60% | 4.5 °C |
| 12 °C | 80% | 8.7 °C |
| 15 °C | 70% | 9.6 °C |
Two things stand out. Drying the air does more than you might expect: at 12 °C, dropping the humidity from 80% to 60% moves the dew point down by about four degrees. And a warmer garage is not automatically a drier one. A heated garage at 15 °C and 70% humidity has a dew point near 10 °C, which a thin steel skin on a winter night can easily drop below.
Why Metro Vancouver garages sweat so much
Prairie winters are colder, but the air there is dry. Our problem is that the outdoor air is mild and wet for months at a time. Environment and Climate Change Canada's 1981–2010 climate normals for Vancouver International Airport show:
- A mean daily temperature of 4.1 °C in January and 3.6 °C in December, with mean daily lows of about 1.4 °C and 0.8 °C.
- Average 6 a.m. relative humidity of about 89% from October through January, and still around 81% at 3 p.m. in December and January.
- About 18 days with measurable rain in each of December and January, and roughly 186 mm of rain in an average November.
- About 12 nights in December when the low reaches 0 °C or colder.
Put those together and you get a long season where a plain steel door sits only a few degrees above freezing while the garage air, fed by damp outdoor air and whatever you bring in, is closer to saturation. The condensation is predictable rather than a fault.
Where the extra moisture comes from
DASMA lists three common sources of higher humidity inside a garage: a wet or snow-covered car, a humidifier, and moisture from a laundry or washing area next to the garage. On a rainy coast, the car deserves a close look. A car that's been driven through rain carries water on its body, in its wheel wells and on its tires. All of that evaporates into a closed garage overnight. Wet coats, bikes, a drying rack and an unvented dryer add to it.
Condensation, fog or a leak? How to tell
Before you fix anything, work out which problem you actually have.
Condensation on the panels
That's condensation, not a leak. Warm, damp air inside the garage touches the steel skin, which sits close to the outdoor temperature, and the moisture in the air turns to water on it. DASMA, the North American door manufacturers' association, says garage door condensation is not normally a product defect.
Look for fine droplets spread evenly over the inside face of the steel, worst on cold, still nights and after you park a wet car. It shows up on dry days too. The outside face is dry. Wipe a section dry in the evening; if it beads up again by morning without rain, it's condensation.
Fog between the panes
Garage door windows can collect droplets on the inside face just like the steel, even when the glass is double- or triple-pane. That alone isn't a fault.
Fog trapped between the two panes of a double-pane unit is different from droplets on the inside face. DASMA says fogging may point to a failed glazing seal, and because the glass is built into the door section, a trained door technician should look at it.
A real water leak
Leaks follow the rain. Look for water entering at the bottom corners, under a worn floor seal, at the jambs, or running down from the header above the door. The water tends to collect in one spot instead of covering whole panels. If you see daylight at the bottom of a closed door or along its edges, the perimeter seals need attention, which is a separate job from controlling condensation.
What actually helps with garage door condensation
DASMA's tips for controlling condensation on sectional garage doors are short. Keep the garage properly ventilated to control humidity. Turn the garage air temperature down during extreme cold. Use only the glass cleaners the door maker recommends, so the glazing doesn't degrade. Keep the seals tight around the glazing and between the door sections. Here's how that plays out in a typical Lower Mainland garage.
Cut the moisture first
- Let a soaked car drip for a few minutes on the driveway before pulling in, or leave the door open a short while after parking if it's safe to do so.
- Don't dry laundry in the garage, and make sure a dryer in or next to the garage vents outdoors.
- Run a dehumidifier if the space is used as a workshop or gym. As the table shows, lowering humidity drops the dew point quickly.
Ventilate the room, not the door
DASMA Technical Data Sheet 173, Garage Doors and Ventilation, is useful here. It notes that the garage door opening is usually more than 4% of the garage's floor area. That means it can serve as a "natural vent" in its own right, and "vents in garage doors should not be needed for natural or passive ventilation." Opening the door for a short time on a dry afternoon, or using a wall vent or an exhaust fan, moves damp air out without touching the door's structure.
Keep the inside skin warmer
An insulated door has a second steel skin on the inside, with foam between the two. DASMA describes a "thermally-efficient door" as one with an insulated core and a thermal break at the meeting rails, which is a non-metal material that breaks the heat path from front to back. That keeps the inside skin much closer to the garage temperature, so it's less likely to fall below the dew point.
So will an insulated garage door stop condensation? It usually reduces it, because the foam and a thermal break keep the inside skin closer to the garage air temperature. It won't stop it in every case. DASMA notes that insulated doors may not perform at the same level as the surrounding walls, and that even double- or triple-pane glass can collect condensation in a humid garage.
Whether a new insulated door makes sense for your house is a bigger question. Our guide on whether garage door insulation is worth it in BC covers that decision.
What doesn't help, and one fix that can hurt
Cranking up a garage heater on a cold night can make things worse. Warm air picks up more moisture from the wet car and the floor, which raises the dew point, while the door skin stays cold. That's why DASMA suggests turning the garage temperature down in extreme cold, not up.
Drilling vents into the door panels is the fix to avoid. Not without the door manufacturer's say-so. DASMA warns that cutting a hole in a section to install a vent can weaken the section and possibly the whole door. It also points out that the door opening itself usually works as the garage's natural vent, so vents in the door should not be needed for passive ventilation.
Wiping the door down every morning treats the symptom. It's fine for a few cold weeks, but if it's an all-winter job, deal with the moisture source and the ventilation instead.
When condensation points to a repair
Most of the time, garage door condensation is a humidity problem, not a door problem. A few signs mean it's time to have the door looked at:
- Fog between window panes that doesn't clear. The glazing seal has likely failed.
- Daylight or drafts at the section joints, or water running out of a joint. DASMA's tips include keeping tight seals between the sections, and a damaged or separated section may need panel replacement.
- Rust on hinges, rollers, brackets or the bottom of the door. Our homeowner maintenance checklist shows what to look at each season.
- Water on the inside after every rain, not just on cold dry nights. That's a seal or flashing issue, not condensation.
DASMA says condensation on garage door glass does not typically affect the durability or structural integrity of the door. The water does have to go somewhere, though. Steel hardware that stays wet all winter is more likely to rust, and water pooling at the floor seal is worth watching.
If you're planning new glass sections, our garage door styles guide explains why full-view glass doors tend to show condensation in a heated garage.
Need someone to look at it?
Up and Down Garage Doors works on residential and commercial doors in Vancouver and across the Lower Mainland. If you're not sure whether you're dealing with condensation, a failed window seal or a leak, book a garage door repair visit and we'll check the seals, sections and glazing. Call (778) 873-7282. Our staff also speak Mandarin and Cantonese. New clients: 10% off labour on your first repair — mention NEW10 when you book (one per household/business, work booked by Dec 31, 2026).