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How to Properly Space Deck Boards

Decking is structural in addition to being an aesthetic element. Decking must be able to support 40 lbs live load + 15 lbs dead load as it is supported between joists. Most decking is designed to be installed across 16" on center joists. You may be required to install 12" on center joists for diagonal decking.

For many years, decking was primarily wood. People used redwood, cedar, pressure-treated pine and even some exotic hardwoods. Wood has some beautiful natural characteristics, but also requires some maintenance. Decking comes in many forms these days. There are over a hundred different man-made decking products on the market today. Most are composed of wood-plastic composite, capped composite, vinyl and aluminum. They offer low-maintenance and a variety of appearances.

Wood decking is commonly available in 2x6 and 5/4 x 6 profiles. 5/4 x 6 is produced specifically for decking and is milled with a radius edge or bull nose. 2x6 is thicker and is stronger, but is also more expensive. Spacing between deck boards provide a few critical functions. The primary function is to drain water from the deck. Gaps that are narrow (1/8”), can catch debris, specifically on top of the joists, and can be difficult to clean out. Larger gaps, such as 1/4”, allow more of this material to fall through the deck. Ventilation below the deck is also enhanced by the gaps between the deck boards, but this is only important in ground-level decks.

For lumber decking, both the moisture content of the lumber and the environment its installed in matter. “Green” lumber with a moisture content of more than 19% can be installed with nearly no gaps in arid environments, and in a few short months, will shrink to a desired size gap. Overall, conventional decking profiles should be installed such that when seasoned, will have gaps between 1/8 and 1/4 of an inch. Look at the ends of the boards and install the decking "barkside" up to prevent cupping. Install decking with 3" pressure-treated compatible deck screws instead of nails. Use two nails for each joist to deck board connection. Locate screws about 3/4" from the edges of boards. Start installing deck boards at the outside of the deck and work towards the house wall. Stagger butt joints as much as possible for a nicer appearance. You may want to predrill the screw holes at the ends of the boards to prevent the wood from splitting. Many deck builders overhand the decking over the frame by about 1/4". You can use a chalk line and circular saw to trim the edges of the decking. Hidden deck fasteners are also an option to create a fastener-free decking surface.

Wood decking will require you to stain your deck at least every year for the first several years to protect the surface from sun and moisture damage. When the decking is installed, it is usually high in moisture content, which can lead to cracks in the wood if it is allowed to dry too quickly.

Wood decking is usually nailed or screwed to the joists for attachment. Alternative decking products have a wide range of hidden fastening systems. Always follow the manufacturer's instructions.

Your choice in decking is very important because it is the surface you will see, walk on, maintain and have to live with for years to come. Do some research on our site to find a material that lends itself to your tastes.

Installing Decking
Installing Decking

Trimming the decking around an angled corner.