Short answer: use nails for framing and joints loaded sideways (in shear), because nails bend before they break. Use screws where pull-out matters, for boards you'll want to remove later, and for decking or siding. Use code-listed structural screws or bolts where a plan calls for lags or bolts. Outdoors, choose by coating: hot-dip galvanized (ASTM A153) or stainless steel. Never use bright, electro-galvanized or interior screws in pressure-treated lumber.
Nails vs screws: what each is good at
A fastener is loaded one of two ways. Shear is the two boards trying to slide past each other, like a stud on a plate or a rafter on a wall. Withdrawal is the fastener being pulled straight out, like a floorboard lifting or a gate board prised off by livestock.
- Common nails are thick, soft steel. In shear they bend and keep holding. They're fast to drive and cheap, and they're what most original extension framing schedules specify.
- Ordinary deck and drywall screws are hardened and thinner. They resist withdrawal well but can snap in shear. Connector makers say not to use them in joist hangers or framing anchors; use the nails or screws the connector maker specifies.
- Structural screws are engineered to replace lag screws, bolts or nails in specific joints. Look for an evaluation report number (often an ICC-ES "ESR" listing) on the box, and follow its spacing.
- Carriage bolts through-bolt joints that see heavy, repeated racking, like gate rails and battens.
Which fastener for which job
| Job | Best choice | Why |
|---|---|---|
| Wall and roof framing | Hot-dip galvanized common or ring-shank nails | Strong in shear, fast to drive |
| Joist hangers, framing anchors | Connector nails or screws the maker specifies | Rated for the connector |
| Siding, board-and-batten, slats | Ring-shank nails or exterior screws | Resist working loose as boards swell and shrink |
| Plywood sheathing and floors | Ring-shank nails or exterior screws | Hold down against squeaks and pull-out |
| Gate rails and battens | Galvanized carriage bolts | Don't loosen under swinging and leaning loads |
| Removable panels, nest box lids, hinges | Exterior screws | Easy to take apart and re-fix |
| Ledgers, posts to beams | Structural screws or through-bolts | High loads in a small joint |
Why ring-shank nails are worth it outdoors
Outdoor wood swells and shrinks with the weather. Each cycle works a smooth nail a little looser. The USDA Forest Products Laboratory's Wood Handbook reports:
- Annular (ring) shank nails resist withdrawal about 40% better than common nails in wood that stays at a steady moisture content.
- When the wood goes through wet-dry cycles, annular and helical (spiral) threaded nails hold about four times better than plain nails of the same diameter.
- Smooth nails driven into green wood that then dries lose a major part of their holding power.
That's why the Slatted Wooden Pallet Bin calls for ring-shank nails on its hardwood slats, and why pallet makers use spiral nails.
End grain and clinching
- Nails driven into end grain hold only 50–75% as well in withdrawal as nails in side grain; screws in end grain average about 75%. Don't rely on end-grain fasteners alone to hold a joint together under pull. Add a block, a cleat or a metal connector.
- A smooth nail driven through and clinched (bent over on the far side) holds far more than an unclinched one. It's the old farm trick for batten doors and feed-box boards.
- In dense hardwoods, drill a pilot (lead) hole about 90% of the nail's diameter. It stops splitting, and the Wood Handbook found it slightly increases holding power too.
Coatings: the part that decides how long it lasts
Today's copper-based treated lumber (ACQ, copper azole) corrodes ordinary steel and thin zinc coatings much faster than the old CCA lumber did. Industry guidance from treated-wood producers:
- Hot-dip galvanized fasteners meeting ASTM A153, and connectors to G185 (ASTM A653) or batch galvanized to ASTM A123, are the baseline for treated lumber.
- Type 304 stainless for very wet locations, and Type 316 where there's salt or salt spray.
- Avoid fasteners labeled "electro-galvanized," G60 or G90 in treated wood. They were designed for an older chemistry.
- Don't mix metals. Use galvanized nails in galvanized hangers and stainless in stainless, or galvanic corrosion eats the weaker one.
Some newer micronized-copper lumber permits lighter coatings in dry, above-ground uses. The lumber tag or the maker's fastener guide is the final word.
Sizing rule of thumb
A traditional carpenter's rule: pick a nail about three times as long as the board you're nailing through, so two-thirds of it bites into the piece behind. For a ¾ in (19 mm) board that's a 2¼–2½ in (57–64 mm) nail, an 8d. For screws, aim for at least 1 in (25 mm) of thread in the second piece, more in softwood.
Frequently asked
Are deck screws OK for a chicken coop?
Yes for siding, sheathing, trim and doors. Frame the walls and roof with nails or with structural screws rated for the joint.
Can I use stainless screws in galvanized joist hangers?
No. Match the metals, and use the fastener the hanger maker specifies.
Do I need special nails for pressure-treated wood?
Yes: hot-dip galvanized to ASTM A153, or stainless steel. Bright and electroplated nails rust quickly in contact with copper preservatives.
Nails or screws for a farm gate?
Carriage bolts at every rail crossing, as in the Five Field Designs and Classic 16-ft Gate plans. Screws and nails work loose when the gate swings.
Fastener performance figures are from the USDA Forest Products Laboratory Wood Handbook; coating guidance follows treated-wood industry recommendations. Always follow your lumber's tag and the connector maker's instructions.