The gauge of nails that you use for installing pine tongue and groove wood on the ceiling of your home is largely unimportant. Several gauges of nails work well for this task. Because the nails are all hidden in the wood, it's possible to even use different gauges of nails.
A nail's gauge represents its diameter. Common gauges for nails used in tongue and groove installation include 15, 16, 17 and 18. The gauge of a nail has nothing to do with its length. As such, it's possible to use 15-gauge nails with lengths of 1 inch, 1.5 inches or 2 inches. As the gauge of a nail increases, the nail is smaller. For example, a 15-gauge nail has a diameter of 0.072 inches, whereas an 18-gauge nail's diameter is 0.048 inches.
The gauge of the nails you use for the installation of a tongue and groove ceiling is unimportant because of the very slight difference in the diameter of different gauges. For example, a 16-gauge nail has a diameter of 0.063, which is only a fraction of an inch smaller than 15-gauge nail and very difficult to notice without using a digital caliper.
The length of the nails is more important than the gauge when using the nails to install tongue and groove wood. The nail must be long enough to go through the piece of pine and into the ceiling above. If the nail is too short, it won't hold the pine tongue and groove securely to the ceiling. If installing one-half-inch pine, use 1 1/2-inch nails. For three-quarter-inch pine, 2-inch nails are appropriate.
When you have the ceiling prepared for the first piece of tongue and groove wood, nail it to the ceiling by putting nails diagonally through the tongue and into the ceiling. Use a pneumatic nailer for this process to allow you to put the nails in place quickly and with ease. When you have secured the first board, push the second board into place so its groove surrounds the first board's tongue. Nail the second board to the ceiling in the same method and continue this process.