Rustproof Wood Siding Nails

DEAR TIM: We are getting ready to install some plain beveled wood siding on a room addition project. As you can see from the photos (not shown in this column), we live next to the ocean. We are afraid of stains. What kind of nails do you recommend that we should use? Are galvanized nails sufficient? Also, do you have any suggestions with respect to nailing the wood siding? N. B.

DEAR N. B.: Does that room addition happen to have a spare bedroom for a traveling columnist? Seriously, I do love the ocean and the ocean environment loves to corrode metal. As such, you should only use one type of siding nail, that being a type 316 stainless steel siding nail. High quality galvanized nails will work in just about every location except for yours.

Galvanized siding nails are available in many different types and grades of quality. There are four types of galvanized nails: mechanical plated, hot-galvanizing, electroplated, and hot dipped. All of these types have a zinc coating which is applied to a standard steel nail. However, the thickness of the zinc coating and manner in which it is bonded to steel varies significantly.

Mechanically plated galvanized nails receive a thin coating of zinc dust which is applied to cold steel nails. Sometimes an extra thin layer of chromate is added to these nails. Hot-galvanized nails are not to be confused with hot dipped galvanized nails. The hot-galvanized nails receive a zinc coating by tumbling steel nails in a drum with small zinc chips. The drum is heated and rotated and the zinc chips melt. However, the coating results are often uneven. The bond between the steel nail and the zinc is not as good as it could be.

Electroplated galvanized nails often are very shiny. The thin zinc coating is applied to the steel in an electrolytic solution. The coating of zinc is very thin. This method is often used for nails that are used in pneumatic nail guns. These nails often begin to rust in short order when exposed to any type of weather.

The best galvanized nails are those that are hot dipped. Steel nails are bathed in molten zinc. The temperature of the molten zinc is so hot that the zinc actually forms an alloy with the outer layer of the steel. The best process involves the nails being dipped a second time. This adds a thick layer of zinc to the nail. If you must use galvanized nails for any outside purpose, only use double hot dipped galvanized nails.

The ultimate exterior nail is stainless steel. These nails are commonly available in two grades: type 304 or type 316. The type 304 stainless steel nails contain 18 percent chromium and 8 percent nickel. These nails will never corrode in most environments. However, ocean spray and mist can contain chlorides which will corrode 304 stainless steel. Type 316 stainless steel contains molybdenum which makes it resistant to attack by ocean water spray or mist.

Nailing your beveled siding is very critical if you want the best results. A large majority of this type of wood siding is often incorrectly nailed. Wood siding will expand and contract in response to changes in moisture content. Because of your ocean location, your siding will be on the move. This movement is greatest across the grain of the wood. The siding must be allowed to move freely with changes in moisture.

To permit this movement, only one nail should penetrate each piece of siding at each wall stud location. These nails must pass through the siding just above the hidden top edge of the piece below. Should you nail into the piece below, you will effectively pin it. Cracks or bulges may appear at a later date. Finally, make sure that the siding nails are long enough to pass through the siding, the exterior sheathing, and into the wall studs a minimum of one and one-half inches.

This column was featured in the May 6, 2014 AsktheBuilder Newsletter.