Why garage doors rust
Most garage doors here are steel. B&D NZ says its sectional doors are most often steel, and Dominator says all of its doors are built from New Zealand steel, with its Series A roller door made in Zincalume or pre-painted steel and COLORSTEEL its preferred pre-painted steel.
That coating keeps the steel underneath from rusting, as long as it is looked after. Dominator says every exposed steel surface needs some care to guard against corrosion, and every maker on this page asks for more washing where the air carries salt or industrial fallout.
Rust starts where the rain doesn't reach
Rain rinses salt off the open face of a door. The parts it misses keep their salt. BRANZ testing on an Auckland building within 500 m of the harbour found that sheltered positions collected about 3 to 8 times more salt deposits than exposed ones.
The makers point at the same spots. Garador says to pay attention to the curtain face next to the door head when washing, and B&D NZ's care guide includes the areas the rain does not reach. New Zealand Steel's COLORSTEEL maintenance brochure, written for roofing and cladding, names "sheltered areas of garage doors" among the places that need washing by hand.
Near the sea, an estuary or a geothermal area
The building standard NZS 3604 sorts sites into exposure zones for corrosion. As MBIE sets it out in Determination 2019/039, Zone D is within 500 m of the sea or harbours, or within 100 m of tidal estuaries, and BRANZ notes that E2/AS1 adds a Zone E for breaking surf beach fronts.
Distance is only part of it. In the same determination MBIE found that a council should have looked at the specific site as well as the maps, and it ruled a house near a tidal estuary to be Zone C, not Zone D. BRANZ has also found that winds off the ocean can carry salt particles more than 20 km inland.
Salt is not the only cause. Garador says to wash more often in geothermal areas, and BRANZ's trials in Rotorua found mild steel 60 m from a fumarole still corroding at a high rate.
How often the makers say to wash a steel garage door
| How often | In salty or harsh air | |
|---|---|---|
| Dominator door care page | Every 14 days, with clean water and a cloth | More often in salty or industrial fallout areas |
| Dominator maintenance sheet (September 2021) | Every 3 months, with clean water and a cloth | More often in salty or industrial fallout areas |
| B&D NZ care guide | Every 14 days, including the areas rain misses | More often, and extra surface protection may be needed |
| Garador door care page | Three to four times a year, or every 14 days for coloured steel doors | More often close to the sea or in geothermal areas |
Two Dominator figures, one door
Dominator's own documents disagree: its door care page says every 14 days, and its September 2021 maintenance sheet says every 3 months. We give both rather than pick one. Follow the care sheet that came with your door, and wash more often than it says if you can see the sea from your driveway.
Washing a garage door the way the makers describe
Use clean water and something soft
Dominator and B&D NZ say clean water and a cloth. Garador says clean water and a soft bristle brush.
Reach the sheltered parts
Work along the top of the door near the head, the bottom rail and any part under an eave or carport roof, because those are the areas the rain leaves salty.
Keep water off the opener
Dominator's door care page says in capitals not to wash the automatic opener. Garador says washing it voids the warranty and could cause electrocution.
Stay clear of the mechanism
Wash the door's face and leave the springs, drums and cables alone. Look at them as you go, without touching.
Put the next wash in the calendar
Use the interval in your own door's care guide, shortened if you live close to the coast or a geothermal area.
Rusty cables, springs or brackets are a door specialist's job
Garador says the lifting cables are under extreme tension, not to touch the drums or cables, and to contact a dealer at any sign of fraying or corrosion. Dominator's maintenance sheet also says to call a dealer about a corroded or frayed cable. Look at them from a safe spot and leave the rest to a door specialist.
How to fix rust on a garage door
None of the makers' care guides we drew on gives steps for treating rust on a door, so this page doesn't either. Ask the maker or your door specialist what suits your door's finish before you sand, treat or paint it.
B&D NZ does say a roller door in salty air may need extra surface protection, which is a fair question to put to whoever services the door. Rust on the tracks or brackets, or a bottom rail that is flaking, is a garage door repair. Panels or a curtain rusting right through usually points to replacing the garage door.
Does the warranty cover rust?
Usually not where salt is to blame. Dominator's door warranty statement does not cover damage to surface coatings, base materials or motors caused by being close to the seafront or similar corrosive conditions, and its 10 Year Total Confidence Warranty leaves out corrosion and damage from salty or damp conditions.
Upkeep counts as well. Dominator's door care page says the warranty may be void if correct maintenance and servicing are not carried out, and Garador says maintenance is in most cases needed to keep its warranty valid. Within those terms, Dominator's standard warranty covers the steel curtain and surface coating of its Series A roller door and Flex-A-Door for 5 years.
What to tell the door specialist
- Where the rust is: the face, the bottom rail, the tracks, the brackets or the cables
- How close you are to the sea, a harbour, a tidal estuary or a geothermal area
- The make of the door and roughly when it went in
- Whether you still have the warranty paperwork
- Photos of the rust, taken from a safe spot
What you can do, and what to leave
You can
- Wash the door on the interval in its care guide
- Give the sheltered top and bottom extra attention
- Photograph any rust and when you first saw it
- Find the warranty card and the install date
Leave to a door specialist
- Corroded or frayed cables and rusty springs
- Rusting tracks, brackets and fixings
- Advice on treating or protecting the finish
- A door that is rusting through
What we would do
Each time you wash the door, take a photo of the bottom rail and the inside face and keep them in one album on your phone. If rust appears you'll know when it started and how fast it is spreading, which helps with the warranty conversation and tells the door specialist how far it has gone.