How to Choose Nails for a Nail Gun: Gauge to Job

Nail gauge is just the shank thickness, and a smaller number means a thicker, stronger nail. The gauge you need is set by how much holding power the job requires and how big a hole you can tolerate.

The ladder runs: 18-gauge brads for light trim and molding, 16-gauge finish nails for baseboard, casing and crown, 15-gauge angled finish nails for door jambs and thick hardwood trim, and full-size framing nails (around .120 to .131 in shank) for structural walls and subfloor. Pick the thinnest gauge that will actually hold, because thinner leaves a smaller hole.

Collation is how the fasteners are stuck together into a strip, and it must match your nailer exactly. Finish and brad nails come in straight strips (16ga and 18ga) or angled strips (15ga and some 16ga); framing nails come in 21-degree, 28-degree and 30-34-degree strips.

You cannot load a 30-degree strip into a 21-degree gun, or an angled finish strip into a straight magazine. Angled magazines and steeper framing angles buy you access into tight corners. Before buying nails, read the angle and gauge printed on your nailer or in its manual.

A fastener should pass through the material you are attaching and sink at least twice that thickness into the material behind it. For 3/4 in trim into a stud, that means roughly 2 to 2-1/2 in.

For framing, 3-1/4 to 3-1/2 in nails are standard for nailing 2x stock together. Too short and it won't hold; too long and you risk blowing through the back side or hitting wiring and plumbing.

Bright (uncoated) nails are interior, dry-use only, they rust fast outdoors and react with the chemicals in pressure-treated lumber, bleeding stains through paint.

For covered exterior or damp interior work, choose electro-galvanized or hot-dip galvanized. For exposed, coastal or pressure-treated applications, spend up for stainless steel. Matching coating to environment is what keeps trim from rust-staining a year later.

Staples add a second leg and a crown, so they hold thin and flexible material a single nail would pull through. Narrow-crown 18-gauge staples are for upholstery, cabinet backs, drawer bottoms and lattice.

For structural sheathing and subfloor, do not use a narrow-crown finishing staple, step up to a wide-crown 16 or 15.5-gauge construction staple rated for the job, and confirm your local code allows staples for that connection.

18ga brad: thin trim, molding, shoe base, cabinet faces. 16ga finish: baseboard, casing, crown. 15ga angled finish: door jambs, thick and hardwood trim.

21 or 30-degree framing nails: walls, subfloor, structural framing. Narrow-crown staple: upholstery and cabinet backs. Buy the thinnest fastener that holds, and match collation and coating before length.