Fasteners for exterior wood: what holds up and what rusts out
By Jeff Rabkin, JustFix Wood · Published September 28, 2026
A lot of the loose rails and popped boards I'm called out to fix aren't a wood problem. They're a fastener problem. The board is fine — the screw holding it rusted away or the nail worked loose.
Treated lumber eats ordinary steel
Modern pressure-treated lumber is treated with copper-based preservatives, and copper corrodes plain steel fasteners. Put a cheap bright screw or electro-plated nail into treated wood and within a few years you'll find rust streaks, black staining, and fasteners you can pull out with your fingers.
For anything going into treated lumber, the fastener needs to be rated for it: hot-dip galvanized, ceramic-coated, or stainless steel. The little coating on cheap plated screws isn't enough.
Screws, nails and bolts — where each belongs
- Deck boards and railings: coated or stainless deck screws. They hold better than nails and are easier to back out when a board needs replacing.
- Joist hangers: only the special hanger nails or structural screws rated for hangers. Drywall screws have no place in a structure — they're hard and brittle and snap.
- Ledgers and posts: through-bolts with washers, or structural screws rated for the load. This is where the deck attaches to the house; it's the connection that matters most.
- Fence rails and gates: coated screws for pickets, lag bolts or carriage bolts for posts and heavy hinges.
Signs the fasteners are the problem
Look for rust streaks running down the boards, black stains around screw heads, boards that rock underfoot, and nails that have popped up an inch above the surface. Push on rail posts — if the movement is at the fasteners rather than the wood, the repair is often quick and cheap.
What I use on repairs
I match the fastener to the wood and the load: stainless near the ground and where staining would show, coated structural screws for framing connections, proper hanger nails in every hanger. It costs a little more than box-store screws, and it's the difference between a repair that lasts and one I get called back to.
If your deck or fence is loose and you're not sure why, send photos of the connection points. Half the time it's hardware, not lumber.
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