Cut nails bring a bygone air to wood floors, doors, cabinetry, or fencing. With their heads showing on or above the surface of the wood, cut nails provide the look of early American construction. Granted it may cost one-third more to finish a floor with cut nails, but they are the ideal accent for a period home or décor.
Authenticity and Style
Like nails made during the 19th century, cut nails are sheared by machine from steel plate, producing a nail with a distinctive wedge shape that ends in a blunt point. It is this particular profile that gives the nail its authenticity. Cut on all sides to produce four edges, they’re often called “square nails.” The characteristic square head looks distinctive on a wood floor.
Beyond this, the differences between nails are subtler. Nail design varies mostly in the length of the shank and the size and shape of the head, which is proportionate to the shank. Shanks measure from 1 to 4 inches on up to 8 inches for post and beam. Nail heads are determined by the type of nail (finishing, flooring, etc) and style. Nail heads can be domed, flat, hammered for an authentic look, or have a bump for decorative purposes. Wider heads are used for face nailing floors, siding, doors, and fences while small or non-existent heads are used for delicate work, molding, and tongue-and-groove flooring. Sometimes the nails are meant to be clinched (bent at a 90-degree angle after the nail has passed through wood) for use on wide flooring and batten doors. When ordering these, be sure to mention that the nails will be clinched so that the metal won’t be tempered.
Strength and Staying Power
True handmade nails provide the greatest authenticity and an even greater holding power than a machined cut nail because the surface is irregular. With flat spots and rounded areas, hand cut nails tend to rip and grip the wood. Unfortunately, they are prohibitively expensive when it comes to the number of nails needed for a floor installation. As a compromise, it is possible to get a slightly more expensive decorative wrought-head nail with a three-sided head and black oxide coating. These nails are designed to simulate the nails hand-forged by farmers in their backyards during the 1700′s.
Machine-cut nails also provide superior grip because they tear through wood fibers instead of splitting the wood. A slight variation on the straight-edged nail is the belly nail that bows out in the center. As the nail is driven into the wood, the broad middle rips a path that gets closed up around the head as it’s pounded in. Its irregular shape keeps it from pulling out.
Since cut nails have blunt ends, there’s a bit more work involved in putting them in. While no particular type of hammer is needed, cut nails must be installed manually. With no pneumatic nailers, the cost of the project adds up if you’re using an installer. Installers should be experienced in cut-nail installation.
It’s very important to nail with the grain to avoid splitting the wood. The wider side should always go with the grain. To drive a cut nail, start with short, tapping strokes until the nail is securely in place. It’s important to be careful with the heavier, driving blows that follow because a cut nail is more brittle than common round nails. If it does become bent it must be straightened carefully. If it snaps, a cut nail leaves a pointed tip in the wood that’s difficult to remove. Pre-drilling pilot holes can help ward off problems, especially at the butt ends of boards where splitting is most likely to occur.
On flooring, which makes up over 50 percent of cut nail use, nailing is the same as with round nails. Thinner boards take a nail 3/4-inch from each side to prevent curling while boards wider than 12 inches take three nails. For tongue-and-groove flooring a slim shank is used to avoid splitting the groove. Nails should be spaced 8 inches apart on 3/8-inch-thick material and 12 inches apart on 3/4-inch flooring. To retain an older look, there are short decorative nails that are pounded down to the desired height but that don’t go into the sub-flooring.
When sanding a floor with cut nails, keep in mind that sanding will abrade nail heads. Countersink the nail to avoid shaving off the decorative head. A one-eighth-inch depth is enough. Pre-sanding the floor to allow for a nail head at floor level or slightly above is another option. To do this the floor must first be secured with blind nailing or glue, and sanded. Then the cut nail can be hammered in as part of the finish process. This is very time consuming. While it’s possible to buy pre-sanded wood, it will still require some sanding. Wood shrinkage can cause nails to work themselves up, but this is usually because the nails were too short. Should this should occur, the nail can be tapped down.
Caring for Cut-Nail Floors
Sometimes authenticity takes a back seat to practicality. In damp or coastal regions, and for exterior work, the biggest enemy to traditional cut nails is rust. While simple maintenance can protect the nails indoors, this can become difficult outdoors. Polyurethane or tongue oil will protect indoor floors from a busy family, wet dogs, damp mopping, and spills. If water hits the floor, it need only be wiped up. Outdoors, however, most people opt out of the extra maintenance by having the nails galvanized. While this does prevent rusting, it should be noted that a galvanized nail could stain wood due to the chemical reaction between the wood and zinc. This is particularly common with cedar and redwood.