What bolts do I use for outdoor furniture?
Use hot-dip galvanized (HDG) or stainless steel carriage bolts. Hot-dip galvanized is fine for most outdoor furniture. Stainless steel (316 grade) is the better choice near saltwater or in high-humidity climates.
Why carriage bolts?
Carriage bolts have a smooth, domed head with a square shoulder beneath. The shoulder bites into wood when tightened, preventing rotation — you can tighten the nut without holding the bolt head. This makes them ideal for furniture assembly where one side is inaccessible.
Galvanized vs stainless
| Finish | Best environment | Notes |
|---|---|---|
| Hot-dip galvanized (HDG) | Inland, suburban, general outdoor | Thick zinc coating; less expensive than SS |
| Mechanically galvanized | Light outdoor use | Thinner coating — not ideal for permanent structures |
| Type 304 stainless | Humid or occasional wet environments | Resists rust well; slight risk of pitting in salt air |
| Type 316 stainless | Coastal, marine, or pool-adjacent | Best corrosion resistance; highest cost |
Zinc-plated (electroplated) hardware is silver and shiny at the hardware store but will show orange rust streaks after a single winter season outdoors. Avoid it for any permanent outdoor installation.
Sizing guide
Most outdoor furniture uses ¼″–⅜″ diameter bolts:
- Light furniture (chairs, benches) — ¼″ × 2″ to 3″ carriage bolt
- Tables and framing — ⅜″ × 3″ or longer
- Structural connections (deck bench frames) — ½″ hex bolt with washer and lock nut
Hardware to match
Use matching material for nuts and washers. Stainless bolts with galvanized nuts can galvanically corrode over time where different metals contact in the presence of moisture.