What Size Nails to Use for Deck Boards, Framing, Railings? (2023)

Building a deck is a great way to expand your living space and take advantage of the outdoors. Once everything is planned and the wood selected, you have to decide what size nails to use for decking, framing, and railings. A quick trip to the local hardware store can leave you feeling like a deer caught in the headlights. There are hundreds of nails!

There isn’t a one-size-fits-all answer. Use 10d (3”) or 16d (3½”) nails for framing, 10d or 12d (3¼”) for 5/4 deck boards and 16d for 2-inch planks, and 6d (2”), 8d (2½”) or 10d for railings. Always use galvanized or stainless steel spiral or ring shaft nails to fasten pressure-treated, cedar, or redwood boards.

In this article, we’ll walk you through the nail aisle and explain nail sizes, types, and what nails to use for the different parts of deck construction. We’ll also take a look at the types of nails to use for different decking materials, and whether to use a nail gun or not. Once you’re in the swing of things, you’ll be able to select and hammer home proper nails for your deck project.

Understanding Nail Sizes

There are several ways nails are labeled and sold depending on the hardware store and where you live. Engineers, architects, and trades also identify nail size on drawings to ensure the correct fastener is used to support the calculated load or stress. So, understanding nails sizes is a good place to start.

The Industrial Fastener Institute and the federal Fastener Quality Act ensure that nails and other fasteners are standardized for quality, composition, and dimensions. Fasteners, like nails, join and support a multitude of structures, so standardization protects us all. The diameter and length of the nail shaft and even the dimensions of the nail head are standardized.

Nails may be identified with a number and the letter ‘d’ or by length and gauge. The ‘d’ is abbreviated from the Latin word for ‘penny’ and historically identified a quantity of handmade nails of a fixed length. For example, a fixed quantity of ‘2d’ or 1-inch nails would once have cost 2 pennies, and the same quantity of ‘16d’ or 3½-inch nails would have cost 16 pennies. So if someone needed a 2-inch nail, they’d look for a 6d or 6 penny nail.

The ‘d’ or penny designation is still used, but thankfully most manufacturers and retailers also identify nails numerically by length and gauge. The longer the length, the more metal to wood contact, so the stronger the grip connection. The smaller the gauge means the bigger the diameter, which results in greater shear strength.

Gauge

The gauge is commonly used to identify the diameter of a nail which influences the shear strength. However, the gauge is inversely proportional to the diameter, which can be confusing. It’s best to remember that the larger the gauge, the narrower the nail or smaller the diameter.

For example, a 2d nail is 1-inch long and commonly 15 gauge or 9/125” or 0.072” or 1.83mm in diameter while a 30d nail is 4½” long and 5 gauge with a diameter of 11/50” or 0.22” or 5.59mm. The thicker metal makes it harder to cut or shear, so a stronger vertical bond. Diameter influences the use and purpose of different nails.

It should be noted that while the gauge affects the shear strength, nails of the same length aren’t all the same diameter. A 2d or 1-inch nail may be 0.0413” or smaller or even 0.148” or greater in diameter. The small diameter is less likely to split thin wood for finishing trim, while the larger diameter will have greater shear strength for supporting and fastening things like joist hangers.

Length

The length of the nail shaft influences the diameter or gauge, as does the type or purpose of a nail. A longer shaft means greater metal to wood connection, which means a better fastening grip strength between wood layers. A 2d or 1” nail is much easier to drive or pull out – less grip strength – than a 16d or 3½” nail. However, longer nails commonly are greater in diameter and are more likely to split thinner wood than shorter narrower nails.

The length of the nail also determines its use and vice-versa. Using a 3½” nail (16d) to join two 2x6s together is one use, but using the same nail size to attach a flimsy piece of trim isn’t. Whereas, a 1” nail wouldn’t hold two 2x6s together, but may be better for the door trim.

It is important to use the correct nail length and gauge or diameter for the task. The nail should go through the piece or two being joined, but only 1/2 to 3/4 of the way through the last piece.

Types of Nails for Decks

Selecting the correct nail length and gauge for different projects is important, as is choosing the appropriate type of nail. Different names are used to label nails based on design, manufacturing features, treatments, and function.

Common Nails

Common nails are manufactured from iron or steel wire and have a smooth 1” (2d) to 6” (60d) shank with a diamond-shaped, 4-sided point. The shafts are thicker than box nails of similar length and have greater shear strength. There are also 4 to 6 ribs or notches on the shaft below the head to improve grip strength. The nails have a flat round head and are frequently used in construction and may be driven by a hammer or nailer.

Box Nails

Box nails are similar to common nails but have thinner shaft diameters. The nails have a flat round head and also have the dimples or ribs near the head for improved gripping. Box nails are generally 1 to 3½” long. They are used for lighter building – non-structural – tasks such as wooden boxes or frames where the narrower shank is desirable to prevent splitting.

Finishing Nails

Finishing nails are used for finishing work. They have a smooth narrow 1” to 4” shaft and a slightly wider barrel-shaped head. The narrower shank is less likely to split thin wood, and the head can be countersunk below the surface with a nail set.

Ring Nails

The shaft on a ring nail has rings or ribs covering the bottom 3/4 of the shank from the point to improve grip strength. The wood fibers move into the channels to hold the nail in place. The nails are harder to drive into and withdraw from wood. Ring nails are commonly used for plywood, OSB, underlay, siding, and shingles.

Spiral Nails

Spiral or twisted shaft nails drive into wood similar to ring nails but are more difficult to pull out. They turn or twist as they are driven in and have greater grip force than most other nails, making them a construction favorite.

Galvanized Nails

Many types of steel or iron nails are available in galvanized formats. The process of galvanization melds a coating of zinc to the nail. The thickness of the zinc layer affects how corrosion resistant the metal is. A smooth-faced hammer or nailer is recommended as a milled faced hammer can chip the zinc coating.

Stainless Steel Decking Nails

Nails manufactured from stainless steel wire are very corrosion resistant and thus, expensive. They are ideal for cedar or redwood decking as they don’t oxidize and stain the wood.

Hot-Dipped Galvanized Nails

Hot dipping is a process that fuses zinc to iron or steel nails by submerging them in molten zinc for a rougher but more even coating. Double dipped nails receive a second bath of zinc for added protection from corrosion. Dipped nails have a rough, dull gray finish which is up to 10 times thicker than the electroplated finish.

ElectroGalvanized Nails

Electro-galvanized nails, also known as electroplated or cold-galvanizing, are galvanized using an electric current. They have a smoother shiny surface than dipped nails. However, the coating of zinc is thinner, making them less expensive but more susceptible to corrosion. They are not suitable for pressure-treated wood, cedar, or redwood.

How to Read Nail Sizes

When purchasing nails it is important to understand what the information on the label is telling you. Some information like who the manufacturer is and where they were made is often on the label, as is the quantity. Other labels identify the length, diameter, head shape, and type of nail pictorially or in words.

You may encounter packages that identify the contents in an abbreviated format, such as 10d5HDG – which translates to 10d or 3” nail in a 5-pound package, and the nails are Hot Dipped Galvanized. The label may also suggest what the nails can be used for; including joist hangers and brackets.

What Size Nails to Use for Decking

Nails are used for connecting material together such as buildings and decks. The better the nail quality, the longer the nail will last and the structure will stay standing. Selecting the right nail for what you’re doing is an important factor.

Deck Framing

Deck framing is often 2×6 or 2×8 or larger 2 by lumber and is commonly pressure treated for outdoor use. Hot-dipped or double-dipped galvanized or stainless steel nails should be used with pressure-treated lumber. Nail length, diameter, and type need to be considered.

When connecting lumber you don’t want the nails to poke through, so the length is important. Additionally, the diameter influences the shear strength of the connection. If the lumber flexes or pulls use ring or spiral nails to improve holding strength and keep pieces together.

Use 10d (3”) hot-dipped (HD) or double-dipped (DD) galvanized or stainless steel (SS) common spiral nails for connecting 2 by lumber together. 16d common HD, DD, or SS nails for fastening beams together.

Deck Boards

Deck boards are fastened to the joists and tend to flex with a weight depending on the spacing of the joists. The farther apart the joists are, the more spring in the deck; 12-inch spacing has the least bounce and 24-inch spacing the most. Smooth shaft nails will work loose over time, so ring or spiral shaft nails are recommended.

For cedar, redwood, or pressure-treated boards, dipped galvanized or stainless steel will resist their corrosive content best. For 2” thick decking use 16d (3½”) ring shank or spiral shaft hot or double-dipped common nails. Attach 5/4 lumber to joists with the same type of box nail, but use a 10d (3”) or 12d (3¼”) length. If fastening plywood decking, select galvanized 8d (2½”) or 10d (3”) spiral or ring nails.

Deck Joist Hangers

Joist hangers commonly fasten to a ledger, plate, or rim joist and support and hold a joist in place. The big concern is shear strength, so use 12d (9 gauge) or 16d (8 gauge) spiral or ring nails with double-thick planks or smooth shank 9 gauge-4d (1½”) when fastening to single thickness boards.

Use dipped or double-dipped nails with hangers of the same material, or similar stainless steel fasteners and hangers. Once the hangers are in place, drop the joists in and drive two 16d nails per side diagonally through the hanger and joist into the plank the hanger is attached to.

Railings

Deck railings vary in materials and dimensions, so the type and length of fasteners depend on the railing style being installed. You may want to predrill narrow or thin material to prevent splitting. Depending on the material, use dipped galvanized or stainless steel 6d, 8d, or 10d common nails for rails, spindles, trim, and caps.

Stairs

Stairs must withstand vibration and shear forces, so 16d nails are best to connect the treads to the stringers and the stringers to the deck frame. Use galvanized dipped or stainless nails and hangers.

Using Nails for Different Deck Materials

Untreated steel or iron nails are ideal or most indoor construction using pine, spruce, or fir. However, cedar and pressure-treated lumber will corrode untreated metal. Select the appropriate fastener for the material being used.

Pressure Treated

Use 6d to 16d hot-dipped or double-dipped galvanized or stainless steel nails to fasten pressure treated wood and minimize corrosion. The length of the nail depends on the thickness of the material being fastened. A good practice is to use nails at least double the length of the thickness of the wood – 1½” thick lumber, use 3” (10d) to 3½” (16d) log nails.

Common nails have a wider diameter than box nails and may split 5/4” deck boards. Both nails have round, flat heads that hold better than smaller headed nails. Ring or spiral nails hold better than smooth shaft nails too. Use a 10d (3”) or 12d (3¼”) dipped galvanized or stainless ring or spiral box nail to attach 5/4 lumber to joists.

Cedar

Fastening 5/4” cedar to deck joists using the same method used to attach 5/4 pressure-treated decking is the least expensive method. However, since you spent the money on cedar, you may choose to use metal hidden fasteners for a clean, aesthetic look. Metal hidden fasteners bite into the sides of the lumber and fasten to the joists. They prevent discoloration and splintering nails driven through may cause.

There are different types of hidden fasteners on the market and most attach to the joist nail, screw, or scrail. A scrail drives in like a nail, but can be removed like a screw. Select the method that works best for you, and use non-corrosive fasteners such as dipped galvanized or stainless steel nails.

Composite

Composite decking commonly has grooves or slots along the sides for hidden fasteners to clip into. The groove allows the plank to expand and contract with temperature changes without compromising the structure or surface. It isn’t recommended to drive nails through composite material for this reason. Additionally, nails wouldn’t sit flush and would mar the look of the surface.

Select the hidden clips or fastener the manufacturer recommends for the composite decking you’ve purchased to ensure the warranty requirements are met. Attach the clips using stainless steel or galvanized dipped nails or other fasteners.

Can You Use a Nail Gun on Decking?

Nail guns or power nailers, whether pneumatic, rechargeable, or electric have proven to be an asset in the construction industry. They’re not likely to replace the hammer but do make some tasks quicker. A nailer doesn’t dent the wood with a missed stroke and is less likely to split wood. It also doesn’t require one hand to hold the nail for setting or vibrate the board out of place when striking the nail.

Purchase or rent a nail gun that is capable of firing 2” to 3½” nails for greater versatility. Select hot-dipped or double-dipped galvanized or stainless steel spiral or ring nails. Remember to use the recommended nail strips to avoid damage, and wear safety glasses and ear protection. Nailers are commonly used to secure hidden fasteners and framing pieces, but less frequently used to secure deck boards directly to joists.

The problem experienced using power nailers isn’t with the nailer, but with the material used to collate the nails themselves. Nails are connected with wire, plastic, or paper to maintain the feed spacing and drive angle.

When the nail is fired into the wood, the connecting material either flies around the site (hence, the eye protection) or ends up stuck under the nail head preventing proper seating or sticking above the wood like a flag. The plastic and metal fragments are difficult to remove, and hard on bare feet if missed.

Wire Weld Collated Nails

Wire collated nails have two thin wires melded to them to maintain alignment and spacing. They handle moisture better than paper but can bend and cause a misfire or jam.

Plastic Collated Nails

Plastic collated nails are held together by plastic strips or bands to fix spacing and angle of delivery. The plastic is more flexible and moisture resistant but becomes brittle in the cold. Additionally, the plastic strip is more likely to interfere with nail seating or to leave flags sticking out under the nail head. The plastic band collated nails are more expensive and less likely to jam or cause flags.

Paper Tape Collated Nails

Paper collated nails have a paper strip glued to them to maintain spacing and angle. The paper tends to fire into the wood or waft around the site. The paper seldom interferes with firing or seating, which is why they are more expensive. It is important, however, to keep the paper collated nails dry from both moisture and humidity.

Conclusion

There are many types of nails varying in length and diameter to choose from. Frame with 10d or 1d nails, fastening deck boards to joists using 10d or 12d nails for 5/4 boards, and 16d for 2-inch planks. Finish off the deck with railings assembled using 6d, 8d or 10d nails. Choose spiral or ring shank nails for greater holding or grip, and select hot or double-dipped galvanized or stainless steel to prevent corrosion.

I hope you have a better understanding of nail sizes, types, and treatments, and which fastener to use for framing and securing deck boards. Remember to wear safety glasses when driving nails. If you found the article helpful, please share it with others. As always, your comments and suggestions are appreciated.