Should I use stainless steel or galvanized fasteners for a deck near the ocean?
Short answer
Near the ocean, use stainless steel for anything visible and anything in contact with redwood, cedar or hardwood, and hot-dip galvanized at minimum for structural connectors like joist hangers and post bases. Thin electroplated zinc screws and hangers rust quickly in salt air and stain the wood. Grade 316 stainless resists salt better than 304 and is the safer choice within a mile or two of the beach. Never let stainless and galvanized touch; the pairing corrodes the zinc.
Why fasteners fail first on the coast
Salt air settles on every surface near the beach and attracts moisture. On metal that means a constantly damp, conductive film that accelerates corrosion. Pressure-treated lumber adds a second attack: modern copper-based treatments are more corrosive to steel than the older formulas, which is why hardware ratings changed years ago. Put a cheap plated screw into treated lumber in Carlsbad and you can get red rust in a season, black streaks on the boards and a connection that is quietly losing strength.
The coatings, from worst to best
Electroplated zinc, the bright shiny finish on bargain screws and hangers, is a very thin coating meant for interior use. It has no place outdoors near the coast. Hot-dip galvanized hardware is dipped in molten zinc and carries a much thicker coating; connectors meeting the relevant ASTM standard are the baseline for treated lumber and are what manufacturers specify for most exterior structural connections. Some makers also offer heavier proprietary coatings for harsher exposure.
Coated deck screws, the ceramic and polymer coated products sold for decking, vary widely. The good ones are rated for treated lumber and hold up well inland. Near salt water their performance depends on the coating staying intact, and every driver cam-out chips it. Stainless steel does not rely on a coating at all, which is why it is the long-term answer by the ocean.
304 versus 316 stainless
Both are stainless, and both are far better than any coating. Grade 304 is the common general-purpose stainless and does well in most exterior work. Grade 316 adds molybdenum, which improves resistance to chloride, meaning salt. Within sight of the ocean, in the spray zone, or on a bluff where the breeze carries salt straight to the house, 316 is the right specification. A little farther inland 304 is a reasonable choice. Even 304 can show light tea staining in heavy salt exposure, which is cosmetic and wipes off.
Where each belongs
- Decking screws into redwood, cedar or hardwood: stainless, because these species react with iron and stain black.
- Hidden composite fasteners and clips: stainless or the manufacturer's specified coated product.
- Joist hangers, post bases, hurricane ties: hot-dip galvanized at minimum, stainless connectors where the budget allows or exposure is severe.
- Ledger bolts and lag screws: hot-dip galvanized or stainless, never plated.
- Railing hardware and anything you touch or see: stainless.
- Nails for hangers: the hanger maker's specified nails in a matching coating, because mixing metals in one connection is where trouble starts.
Do not mix metals
When two different metals touch in the presence of moisture, the less noble one corrodes faster. Stainless screws driven through a galvanized hanger will eat the zinc around each hole. Aluminum flashing against treated lumber corrodes rapidly. Keep each connection consistent: stainless with stainless, galvanized with galvanized, and separate dissimilar metals with a membrane where they must meet. Manufacturers publish compatibility guidance and it is worth following exactly.
The cost conversation
Stainless hardware costs several times what coated hardware costs, and on a large deck that is noticeable. It is also the part of the project least worth saving on. Fasteners are a small fraction of the total, replacing them later means pulling up decking, and rust streaks ruin the look of beautiful wood. We specify stainless for anything visible on coastal projects and discuss the structural connectors case by case based on how close the house is to the water.
Related questions
Can I use regular deck screws if I am a few miles inland?
In inland North County, quality coated screws rated for treated lumber perform reasonably on treated or composite decking. Redwood and cedar still stain with anything containing iron, so stainless remains the better choice for those species anywhere.
My deck has black streaks under the screws. Is it rotting?
Probably not. Black streaks are usually a reaction between iron in the fastener and tannins in redwood or cedar, plus a bit of rust. They can be cleaned with an oxalic acid deck brightener, but they return unless the fasteners are replaced with stainless.
Are stainless joist hangers worth it?
Within the first few blocks of the ocean, or on a bluff, yes. Hangers are buried in the structure and are expensive to replace. Farther inland, hot-dip galvanized hangers with matching nails are the usual specification and last a long time.