Driving nails into concrete is no one's idea of a good time, but when there is no alternative, a few pointers can help make it easier and less dangerous. One of the best ways to reduce the effort involved in this task is to drive the nails before the concrete has completely cured. As it ages, concrete becomes dense and hard, so you may not be able to penetrate it without some high-powered help.
Concrete nails bear a passing resemblance to wood nails, but they have thicker shanks that frequently have vertical ribs for easier penetration. Because they are made of hardened steel, they pose a danger to the person driving them -- because striking one with a hammer also made of hardened steel, such as a framing hammer, has the potential to send tiny shards of metal flying through air. These shards can penetrate skin and injure unprotected eyes. Safety precautions include wearing eye protection and gloves, as well as driving the nails with a small sledge hammer, which is made of softer steel than a framing hammer, so it doesn't shatter and throw off metal splinters.
Drive Nails Straight
In order to bind, a concrete nail must penetrate its target dead straight; if it deviates or wobbles while you strike it, it will chip the concrete rather than make a hole. If you're using a concrete nail to hold a piece of wood, such as a two-by-four wall plate, to a concrete pad or wall, the wood usually guides the nail, but you must still take care to center each hammer blow directly on the head. Striking the head at an angle creates vibrations that chip the concrete and ultimately cause failure of the nail.
Drill Pilot Holes
It's relatively easy to drive concrete nails into green concrete, but if you have to nail into fully cured concrete, you may need to drill a pilot hole for each nail. The masonry bit you use to drill the hole should have a diameter at least an eighth-inch smaller than the nail shank -- if it's any larger, the nail won't hold. Always vacuum the dust out of the holes you drill before driving a nail. Otherwise, the dust can lubricate the nail shank and cause the nail to back out over time.
To save time, many builders drive concrete nails with powder-actuated tools. These use a cartridge filled with gunpowder to drive each nail with such force that it can take a ton of leverage to extract it. PATs aren't appropriate for all concrete surfaces -- you can crack the concrete if it's too hard. In order to check, tap a test nail into the concrete surface. If it makes a well-defined dent, you can use a PAT, but avoid the tool if the concrete shatters. To use a PAT, hold it vertically on the wood you are attaching and strike the plunger once with a mallet. Wear face and ear protection, as well as protective gloves.