Choose the board edge first, because it decides everything else: grooved-edge composite boards install with hidden clips and leave a screw-free surface, while square-edge boards are face-fastened with composite-rated screws and are the right choice for stair treads, perimeter boards and visible board ends. Joist spacing then comes from the board maker's installation guide, not from a rule of thumb. This guide shows how to match edge profile, fastener and framing so a deck installs cleanly and passes inspection in Los Angeles, where fall is the main deck-building season.
Grooved vs square edge: which one do you need?
Grooved edge is the default for the main field of a deck. A groove milled into each board edge accepts a hidden clip, so the surface has no visible screw heads and the clip sets a consistent gap for drainage. Square edge has a flat, finished face and edge, so it is used where the edge is seen or where a clip cannot be hidden, and it is fastened from the top. Many decks use both: grooved boards across the field and square-edge boards for stair treads and a picture-frame border.
| Feature |
Grooved edge |
Square edge |
| Fastening |
Hidden clips |
Face screws |
| Surface look |
Screw-free |
Visible fasteners |
| Best use |
Main deck field |
Stairs, borders |
| Board ends |
Need trim board |
Finished edge |
Boards to start with
The composite decking collection carries both profiles. For a grooved-edge field, look at the Enhance Basics Saddle grooved-edge board or the Prime+ Coconut Husk grooved-edge board. For stairs and borders, the Prime+ Coconut Husk square-edge board in an 8 ft. length suits short runs and detail work.
Hidden fasteners for grooved boards
A hidden clip system is the fastest way to install a grooved deck. The ArmorGuard EDGE hidden deck clip is approved for use with leading composite, PVC, capped composite and hardwood grooved boards on wood joists: its gusset fits the board groove and a stainless steel 2-1/4 in. x #7 screw drives into the joist. If you prefer a concealed screw with a plug, the Cortex hidden fastening system uses collated screws and matching plugs for a seamless surface across the deck. Check that any system you choose is rated for your specific board.
Face-fastening square-edge boards
Square-edge boards go down with screws made for composite. The #9 x 2-1/2 in. composite deck screws have a type-17 point that reduces the need to pre-drill, dual threads for driving and holding strength, and a pancake head that avoids mushrooming. For a deeper comparison of screw types, see our wood screws vs structural screws guide.
Joist spacing: what to check before you frame
Composite boards are not as stiff as wood, so the maximum joist spacing is set by the board manufacturer and can be tighter for stairs, diagonal layouts and heavy-use areas. Read the installation guide for the exact board you are buying, then frame to that spacing and to your permit plans. Framing with 16 in. on center is common, but confirm it against the board's span rating before you build, since closing a gap after the frame is built means adding joists.
Framing hardware to match the spacing
Tight spacing means more joists, and every joist needs a rated connector. The joist hangers buying guide explains how to match a hanger to joist size, and the post bases, column caps and corner braces guide covers the connection at each post. For the full build sequence from footings to fasteners, use our deck materials checklist.
Los Angeles notes
LA's strong sun and heat make composite expansion a real planning item: leave the gaps the manufacturer specifies at board ends and against walls, and avoid fastening boards tight to each other. Decks attached to a house, raised decks and stairs are permit and inspection items, so confirm requirements with your local building department. If you are still deciding between wood and composite, our pressure-treated vs composite decking comparison lays out the tradeoffs.
Decking order checklist
- Grooved-edge boards for the field, with a few extra for cuts and waste
- Square-edge boards for stair treads and borders
- Hidden clips, or composite screws, matched to the board
- Joist hangers and hanger nails for the extra joists
- The board maker's installation guide, printed and on site
Conclusions
Pick the edge profile first, match the fastener to it, and frame to the board maker's joist spacing before you cut a single joist. Use grooved boards with hidden clips for the main surface and square-edge boards where edges are exposed.
