What salt air does to a garage door in three years, and how to slow it down

The three-year door

A garage door in Bellville lasts twenty years with ordinary care. The same door, from the same supplier, fitted the same way in Mouille Point, starts failing in three. Nothing about the door is different. Everything about the air is.

Salt air is not a vague coastal atmosphere; it is a fine, constant deposition of sodium chloride onto every surface, and it is worse within a few hundred metres of the water, worse again where there is spray, and worst of all on a door that faces the sea and is never rinsed. It attacks three parts of a garage door in three different ways, and understanding which is which is what lets a coastal door be kept working.

What the salt corrodes, part by part

The motor's circuit board goes first. A board is copper tracks on a resin base, and salt deposition on it — drawn in through the vents by the motor's own heat cycling — bridges tracks with a conductive film and corrodes the copper underneath. The symptoms are erratic ones: the door opens on its own, the remote works from close range only, the motor stops mid-travel. A board in the salt lasts three to five years; the same board inland lasts fifteen. A motor repair on the Seaboard is a board more often than anything else.

The lifting cables go second, and they go invisibly. A cable is a bundle of steel strands, and salt gets into the bundle and rusts it from the inside, so a cable that looks sound on the outside has half its strength. When it lets go the door drops on one side and jams. Stainless cables cost little more and do not do this, and a cable and track visit on the coast replaces galvanised with stainless as a matter of course.

The steel panel goes third, and slowest. A sectional's bottom panel sits in the wet, and salt gets under its paint at the cut edge and lifts it, and the panel rusts from the edge up. Caught at the bubbling stage it is a single panel with a sealed edge; caught later it is a hinge line and a crooked door.

Which parts should be stainless

Hinges, rollers, cables, track brackets, and every screw and bolt that holds any of them. On a new coastal door that is a specification, not an upgrade, and a supplier who fits galvanised on the Seaboard is fitting a door that will need all of it replaced within five years. On an existing door, each of those parts is replaced with stainless as it fails, and after one full cycle the door is coastal-rated without ever having been replaced.

Springs are the exception: a stainless torsion spring is a specialist part, and the practical answer is a galvanised spring with a corrosion-inhibiting coating, inspected on a shorter interval.

The service interval that keeps a coastal door working

Inland, a garage door service every three years is enough. On the Seaboard it is every year, and the service is different: the motor is opened and the board inspected, the cables are checked by feel for the roughness that means internal rust, the bottom panel edge is looked at for the first bubble, and the door is rinsed with fresh water — which is the single cheapest thing a coastal owner can do between services and almost nobody does.

On a holiday let that stands through winter, the service is in October, before the season, because a door that has stood in the damp for five months will not open in December.

Where this applies

From Mouille Point to Hout Bay on the Atlantic side, from Muizenberg to Simon's Town on False Bay, and from Milnerton up the West Coast to Melkbos. A door that faces the water is in the first band; a door a few streets back is in the second and gets the same failures a few years later. The suburbs that get spray, not just air — Mouille Point, Bantry Bay, Clifton, Kommetjie — are the ones where the three-year door is the rule.