Cleats and Staples for Nail-Down Hardwood: Gauge, Length, Spacing and Setting Them Right

Nail-down hardwood depends on thousands of small fasteners, driven through the tongue of each board into the subfloor. Most crews choose cleats or staples by habit and set the nailer by feel. The flooring maker's fastening schedule says something more specific: what gauge and length, how far apart, how close to the ends, and how the tool should be set. Squeaks, cracked tongues and loose boards usually trace back to one of those.

Read the maker's schedule

Every hardwood flooring maker publishes a schedule for its products, and they differ. Mercier's technical bulletin on fastener selection is a typical example.¹ It sets the fastener by product construction and thickness:

• Solid 3/4” (19 mm): cleats or staples from 15,5 ga to 18 ga, at least 1 3/4” (45mm) long.¹ Space them 6 to 8 inches apart, and 2 inches (51 mm) from the ends.¹
• Engineered 1/2” (13 mm): 18 ga to 20 ga cleats, or 18 ga staples, 1 1/4” (32 mm) long, spaced 4 to 6 inches, 2 inches from the ends.¹
• Engineered 3/4” (19 mm): 15,5 ga to 18 ga fasteners, 1 1/2” (38 mm) long, spaced 4 to 6 inches.¹

It adds two rules for every board. Fasten each with at least 2 nails, and do not nail less than 2 inches from the ends, to avoid splitting the tongue.¹ Aacer's instructions for its 3/4" solid strip and plank ask for at least two fasteners per board, 8-10” apart and 2-3” from the ends.² The two schedules differ in spacing. Each applies to its own product.

Wide boards need more than nails

Wide plank floors move more and are more prone to noise. Mercier recommends assisting the nailing of its 6 ½” (165 mm) and 7 ½” (190,5 mm) wide boards with a urethane-based or silane adhesive, to reduce creaking.¹ It describes applying the adhesive with a trowel in bands about 20 inches wide, perpendicular to the direction of installation.¹ Aacer says to always end-glue wide boards, 4” or more, with PVA wood glue.² See silane adhesives for wood floors.

Setting the tool

A nailer set wrong damages the flooring as it installs it. Aacer warns that improper pressure settings, or failure to use the proper adapter, can cause severe damage.² Too little air pressure may not set the fastener and can damage the next board. Too much can damage the tongue, preventing the next board from fitting, and blister the face.² It recommends a regulator on the air line, starting at 70 PSI and adjusting until the fastener sets properly.² It asks crews to fasten a sacrificial board first, check for surface damage, pressure and tongue damage, then destroy that board.²

Mercier makes the setting the installer's responsibility. The striking force, pressure and position must be adjusted so the fastener head sits correctly in its cavity.¹ It warns that cracked or broken tongues may cause cracking sounds or height differences.¹ On prefinished boards, Aacer says to avoid striking the edge with the nailer's mallet, because edge crushing causes cracks and splinters.²

Starting and finishing rows

The nailer cannot reach the first and last rows. Aacer's method for the first rows is to pre-drill and face-nail the groove side, then blind-nail through the tongue at a 45 degree angle.² Where clearance allows, a pneumatic finish nailer with 15 gauge, 1-3/4” nails can blind-nail the starting rows instead.² The last one or two rows are face-nailed after pre-drilling.² Mercier also specifies a 45-degree angle for fasteners.¹

The subfloor holds the fastener

A fastener is only as good as what it is driven into. Aacer's preferred subfloor is ¾” CDX grade plywood. It says not to install over particleboard, waferboard, pressed wood or fiberboard.² It says water-damaged, swollen or delaminated subflooring will not hold fasteners and must be repaired or replaced.² Loose areas should be nailed or screwed down every 6” along each joist.² The USDA Wood Handbook notes that nail withdrawal resistance in plywood is 15% to 30% less than in solid wood of the same thickness.³ That is one reason fastener length and subfloor thickness are specified together.

Noise is not always a defect

Some sound is normal in a nailed floor. Aacer notes that minor occasional noises in mechanically fastened floors are not abnormal, because of structural movement with changing conditions.² Following the instructions minimizes them, but cannot promise a silent floor.² Persistent squeaks, cracking sounds or boards that move underfoot are different. They point to cracked tongues, fasteners that missed the subfloor, or a subfloor that moves. See hollow spots and deflection for the related problem in floating floors.

Cleats or staples

Both appear in the schedules. Mercier lists L- or T-shaped cleats and U-shaped staples for its products, with gauges and lengths for each construction.¹ Aacer's tool list includes a flooring nailer with 2" cleats and a blind fastening machine.² The choice is usually set by the flooring maker, then by the tool and the crew's experience. What matters more than the type is that it matches the schedule for the product, is driven at the right angle, and seats in the nail pocket without breaking the tongue.

A fastening checklist

• Use the gauge, length and spacing in the flooring maker's schedule.
• Keep fasteners off the ends of boards, and at least two in every board.
• Fit the right adapter, regulate pressure, and test on a sacrificial board.
• Add adhesive or end-gluing where the schedule calls for it on wide boards.
• Confirm the subfloor is sound, dry and thick enough to hold the fastener.

Sources

1. Mercier Wood Flooring, “Technical Bulletin #9: Fastener selection table”. icms.mercier-wood-flooring.com/icms/webfolder_download/f5da71d27054c1efe
2. Aacer Flooring, “3/4" Solid Strip and Plank Installation Instructions (nail-down)”. aacerflooring.com/downloads/residential/Installation-Instructions-Solid-
3. USDA Forest Products Laboratory, “Wood Handbook: Wood as an Engineering Material (FPL-GTR-282)”. research.fs.usda.gov/download/treesearch/62200.pdf

General information for the flooring trade. This article was drafted with AI assistance and checked against the sources listed above; the manufacturer's current instructions and the project specification govern any real job. If something here is wrong or out of date, tell us.