There is a particular shade of orange that shows up on the underside of a beach-area deck after enough winters. It starts as a faint bloom at the edge of a joist hanger. Later it becomes a crust. By the time it flakes, the steel underneath has given up a good part of its thickness.
Owners rarely see it. The hardware that ties a house together (joist hangers, post bases, straps, hold-downs, anchor bolts and nails) tends to live in crawl spaces, behind siding, or under decks. In Del Mar, much of it also lives in air that carries salt from the surf.
This note is about that small steel: what affects how fast it ages, where to look, and how to think about replacement without overreacting.
Why salt air is hard on hardware
FEMA’s Technical Bulletin 8, written for metal connectors and fasteners in coastal areas, explains the mechanism simply. Ocean salts collect on metal surfaces and speed up the reactions that cause rust. High coastal humidity makes it worse, and the longer a surface stays damp each day, the higher the corrosion rate. Onshore winds carry both salt and moisture inland.
The bulletin also makes a point that matters for anyone who owns near the water: distance is not a cliff edge. Salt spray in the air is greatest near breaking waves and declines rapidly in the first 300 to 3,000 feet landward of the shoreline. Even so, the bulletin notes studies showing accelerated corrosion as far inland as 5 to 10 miles. It also cites North Carolina tests from the 1940s in which iron samples corroded ten times faster at 80 feet from the shoreline than at 800 feet.
Del Mar’s 2023 hazard mitigation annex rates flood and sea level rise as high-significance hazards for the city. Those ratings concern water, not steel. Still, they describe a place where the ocean is a constant neighbor, and corrosion is one of its quieter effects.
Sheltered steel is not safe steel
A useful idea in the bulletin runs against intuition. It describes exposure classes and observes that partially sheltered areas, such as the space under an elevated house or a covered deck, can corrode faster than surfaces open to the weather. Rain periodically washes salt off exposed surfaces. Sheltered surfaces collect salt and stay damp longer.
For a Del Mar house, that points to a few places worth attention:
- the underside of decks and stairs, especially near the ends of joists;
- crawl-space framing near vents, where outside air enters;
- posts and post bases under covered porches;
- garage and carport framing that’s open on one side.
The Residential Code already expects corrosion-resistant coverings on crawl-space vents, such as corrosion-resistant wire mesh, among its listed options. The framing behind those vents gets the same salt-laden air.
Treated lumber and the coating question
Treated lumber is common at decks, sills and posts, and the chemicals in it are themselves hard on plain steel. The California Residential Code addresses this directly. Fasteners in contact with preservative-treated wood are to be hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper, with staples in stainless. For connectors in contact with treated wood, coating types and weights follow the connector manufacturer’s recommendations, and in their absence, at least ASTM A653 G185 galvanized steel or equivalent.
The bulletin takes that baseline and adjusts it for the coast. For oceanfront and near-shore buildings, its recommendations lean toward thicker galvanizing and, as best practice in many exposures, stainless steel connectors and fasteners. It also warns against mixing dissimilar metals, which can speed corrosion where they touch.
A quiet inspection, twice a year
None of this calls for alarm. It calls for a routine. A modest look in spring and fall covers most of it:
- Start where water and salt sit. Deck undersides, the ends of joists, post bases, stair stringers.
- Look at the steel, then the wood around it. Rust staining that runs down the wood, swelling where nails enter, or wood that has softened around a connector.
- Count missing nails. Connectors work only when their fasteners are present. Heads that have corroded away leave a hanger holding by habit.
- Check the crawl space near the vents. Hangers and straps closest to outside air usually show first. Our journal note on crawl spaces under old Del Mar cottages describes the access side.
- Photograph and date everything. Comparisons over a few seasons tell you more than any single visit.
For second-home owners, this is a good item to add to a caretaker’s seasonal list.
When hardware needs replacing
The bulletin is direct about existing buildings. Where connectors have already been damaged by corrosion, replacement is the only option. It recommends that replacement connectors differ in size or shape, or be fastened in different locations, so they bear on undisturbed wood. It also notes that old fastener holes shouldn’t be reused, and that repeated replacements can eventually damage the wood enough that members themselves need replacing.
That’s why the choice of material at replacement matters. The bulletin’s life-cycle discussion is plain: the labor to install a connector is often similar whatever it’s made of, and a single future replacement typically costs many times the difference in material.
On an ocean-view deck or under a raised floor, that replacement is structural work. It should follow the load path the connector serves, and a careful contractor will coordinate with licensed engineers as needed where posts, beams or hold-downs are involved. The raised foundation repair page covers the framing below the floor.
The steel inside the concrete
Steel inside concrete has its own version of this story. Rust stains, cracks and spalling at a slab edge or foundation wall usually mean reinforcing steel is corroding inside. The salt-air concrete corrosion page explains that process, and our beachfront concrete calendar offers a maintenance rhythm.
What shapes the scope
When connector work is needed, its size tends to follow:
- distance from the surf and the house’s exposure to onshore wind
- whether the hardware is open, partly sheltered or enclosed
- access: crawl-space height, deck height, finishes to remove
- how many connectors are affected, and whether the wood around them is sound
- replacement material and connector style
- engineering for load-path elements and any permits
If you own anywhere in Del Mar and haven’t looked at the small steel in a while, it may be time. When you’d like a second set of eyes, ask for a Free Quote.