Nails are among the oldest and most used fasteners in construction. From timber framing to pallets, roofing and finishing, the right nail type and size determine joint strength and durability. This guide covers the main nail types, how nail sizes work, and which nail to choose for common construction applications.
How Nail Sizes Work
Nail size is measured in two ways. Metric: diameter × length in millimetres (e.g. 3.0 × 60 mm). Imperial (“penny”): the letter “d” (from the Roman denarius) — for example, a 16d nail is about 3.5 mm diameter and 89 mm long. A general rule: longer nails provide more holding power but are harder to drive and more likely to split thin timber.
Common Nail Types
Common nails have a thick shank and are used for general framing and heavy construction. Box nails are thinner than common nails of the same length, reducing splitting. Finishing nails have a small head for trim and moulding. Ring-shank nails resist pull-out with annular rings. Roofing nails have a large head and are often galvanized for weather resistance. Concrete nails are hardened for driving into masonry.
Materials and Finishes for Nails
Most nails are made of carbon steel wire. Bright nails are plain steel, for indoor use where corrosion is not a concern. Galvanized nails (hot-dip or electro) resist corrosion and are used outdoors and in treated lumber. Stainless steel nails are the best choice for marine environments and acidic woods like cedar and redwood.
Nail Selection Tips
As a rule of thumb, the nail length should be about 2.5 to 3 times the thickness of the material being fastened. Use coated or ring-shank nails where withdrawal resistance is critical. For outdoor projects, always choose galvanized or stainless steel. For engineered or structural connections, follow local building codes and engineering drawings.
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Nail Sizes in Detail
The penny system (2d, 4d, 6d, 8d, 10d, 12d, 16d, 20d, 30d, 40d, 50d, 60d) is the traditional inch sizing. A 16d nail is approximately 3.5 mm diameter and 89 mm (3.5 inches) long, and a 10d nail is about 3.1 mm by 76 mm (3 inches). In the metric system, nails are specified as diameter × length, e.g. 3.0 × 60 mm. When selecting by eye, remember that nails of the same length can differ in diameter between types — common nails are thicker than box or finishing nails of the same length.
For load-bearing connections, nail diameter and penetration length are the two key parameters. A general guideline is that at least 2/3 of the nail length should penetrate into the base material, and the nail diameter should be matched to the species and moisture content of the timber. Nail spacing and edge distance follow the applicable building code or engineering design.
Nail Shank Designs
The shank design dramatically affects holding power. Smooth-shank nails are easiest to drive and remove, and are fine for temporary work and light framing. Ring-shank (annular) nails have rings along the shank that grip the wood fibres, offering up to several times more withdrawal resistance — ideal for pallets, subflooring and engineered wood. Spiral (screw) shank nails twist into the wood and are excellent for flooring and crates. Duplex nails have a double head for easy removal, used in formwork and temporary staging.
Coated Nails and Their Uses
Cement-coated nails have a resin coating that improves grip and lubrication during driving. Vinyl-coated (bright vinyl) nails are common in pneumatic nailers. Galvanized coatings come in two types: electro-galvanized (thin, bright) for light indoor use, and hot-dip galvanized (thick, rough) for outdoor, marine and treated-lumber applications. For cedar, redwood and other acidic woods, stainless steel nails are strongly recommended because galvanized coatings can corrode quickly.
Choosing the Right Nail for Each Application
For framing and structural timber, use common or box nails with adequate penetration. For finish work — baseboards, crown moulding, window casings — finishing nails are countersunk and filled, or brads (small finishing nails) for light trim. For roofing, use roofing nails with a large head and galvanized or stainless shank to resist weather. For concrete formwork, duplex nails allow easy stripping. For pallets and crates, ring-shank nails prevent pull-out during transit. When in doubt, choose a slightly longer nail and a corrosion-resistant coating.
Nailing Techniques
Pre-drilling prevents splitting in hardwoods, near edges and in thin stock. Angle nailing (toe nailing) strengthens joints in framing. Use a nail set to drive finishing nails below the surface without damaging the trim. For pneumatic fasteners, match the collation type (coil or stick) and nail gauge to the nailer. Overdriving or underdriving reduces holding strength — set the depth adjustment so the head sits flush or slightly below the surface.
Sourcing Nails in Bulk
When ordering nails for a project or inventory, specify: (1) type (common, box, finishing, ring-shank, roofing, duplex, etc.), (2) size (penny or metric diameter × length), (3) finish (bright, electro-galvanized, hot-dip galvanized, stainless), (4) packaging (25 kg cartons, 1 kg boxes, coils for pneumatic tools), and (5) quantity. Fastener Hall supplies nails in standard export packing with material certificates, and can produce custom sizes for OEM projects.
Frequently Asked Questions
- What is the strongest nail type? Ring-shank nails offer the highest withdrawal resistance in wood; hardened concrete nails are strongest for masonry.
- Can I use galvanized nails with treated lumber? Yes — use hot-dip galvanized or stainless steel nails; plain steel corrodes quickly in treated wood.
- How many nails should I use per joint? Follow the engineering design or building code; generally more nails add strength up to a code-limited spacing.
- What is the difference between a nail and a screw for wood? Screws have stronger withdrawal resistance and are removable; nails are faster to install and better for shear loads in framing.
- Do you supply nails for pneumatic nailers? Yes, collated nails (coil and stick) are available in common gauges and lengths.
