Joist Spacing for Composite Decking

Before building a composite deck, always read the installation instructions from the manufacturer, paying special attention to the required joist spacing for composite decking. Most composite decking materials, like Trex composite decking, require minimum joist spacing for composite decking at 16″ on center spacing for straight decking and 12″ on center joist spacing for 45-degree angle diagonal decking.

Also, many composite decking materials require 12″ or even 10″ on center stair stringers spacing to support composite stair treads. If you are installing composite decking over an existing frame, you may need to install new intermediate joists or stair stringers to meet the installation requirements.Since most composite products aren’t as inflexible as their wood counterparts, they don’t hide imperfections in the framing quite as well. This can sometimes cause an uneven surface. That’s why stretching a string across the joist spacing for composite deck boards can help detect spots that may be higher than others. These spots can be addressed with a power hand planer to give you a nicer, smoother surface for the deck of your dreams.

Laying out the first joist position on an angle.

Using a scrap piece of wood as a guide to locate the first joist in the situation of an angled corner.

Use a sharpie or construction pencil to mark your joists.

Marking joist locations at 16″ on center spacing on the header with a marker.

Toe nailing a joist to the rim joist.

Installing a joist over a beam. Make sure the top of the joist is flush with the header. Toe nailing will fail in 75+ mile per hour winds. Use hurricane clips in high wind areas.

Use a chisel to notch beams to create a level frame.

Notching a joist over a beam. This joist was 1/4″ higher than all the others. You can notch out a section of the joist or add shims to a narrow joist to even out the top of the deck frame.

Always fill all the nail holes for deck hardware.

Using a palm-nailer or hammer to install joist hangers with 1-1/2″ teco nails to the ledger board.

Inspect the board and trim off the rougher edge.

Measuring the 2×10 pressure treated joist length to prepare for cutting. Use a speed square to square off your joists.

Lift with your knees!

Installing 2×10 pressure treated joists at 16″ on center. Be sure to install the joists crown side up.

You can use a pneumatic palm nailer.

Installing a Simpson Strong Tie H2.5Z Hurricane Tie for every joist to beam connection.