On a door within sight of San Diego Bay, the panels almost always outlive the hardware. A steel skin is coated on both faces and sheds salt reasonably well. The parts that carry the door are bare or lightly plated steel, they move, and they hold moisture in every crevice. So a door on a Harborside street can look presentable from the sidewalk while the parts holding it up are half gone.
A lift cable rots from the middle out
Lift cable is galvanized rope. The zinc protects the outer wires it actually covers, and it never reaches the core strands buried inside the lay. Salt-laden moisture wicks in between the wires and stays there, so corrosion starts where nobody can see it and works outward. A cable can read as serviceable from three feet away, take a fingernail without shedding a strand, and still have lost a large share of its cross section.
Two spots go first. The loop at the bottom bracket sits inches above concrete that stays cool and damp until mid-morning. The bend where the cable enters the drum flexes on every trip, which opens the lay slightly and lets moisture deeper in. Get a flashlight on both and look for rust weeping out from between wires, and for a length that has gone slightly slimmer than the rest. Either one means the cable is finished no matter how the surface looks.
Coils, pins and brackets
Spring coils pit. A pit is a small crater in the wire, and the steel around it now carries what the missing steel used to. Every pit is a stress point, so a spring wound for the cycle life described in CPSC counterbalance guidance gives back only a portion of it once the surface has gone rough. Springs near the water break early rather than break differently.
- Hinge pins seize in their barrels, the section stops articulating, and the roller gets dragged sideways at the curve.
- Bottom brackets rust where the flange meets the slab and water sits in the joint.
- Galvanized track spots along the lowest eighteen inches, then rollers run on rough steel.
- Fasteners lose their heads, so a hinge screw shears off instead of turning.
What that means for what you buy
Hardware this close to the water gets judged on age and exposure rather than appearance. A replacement cable pair sits at an estimated $145 to $245. A drum or end bearing is an estimated $165 to $275, hinges and brackets an estimated $110 to $195, a roller set an estimated $125 to $225, and a single torsion spring an estimated $185 to $320. Guide figures for planning rather than quotes.
None of those corroded parts belong on a homeowner list. Torsion springs, extension springs, both lift cables, the cable drums and the bottom brackets are under load whenever the door is down, and corrosion makes them less predictable rather than more. A bracket bolt backed out of a rusted flange can release the whole load at once.