Composite deck installation, built to the product’s rules

Lock the product before the frame is designed

Composite brands and product lines specify maximum joist spacing — often tighter when boards run diagonally — and many require a solid blocking pattern at ends or where picture-frame borders meet field boards. That spacing has to be in the framing plan before posts go in, not negotiated after the joists are set.

Watch for: A frame already built “standard” with the composite choice still open. Changing product later can force sistered joists or a second layer of sleepers, which costs more than deciding first.

Substructure for composite still follows code

Footings, ledger flashing, structural connectors, guards and stairs are code-governed the same way they are on a wood-surfaced deck. Composite does not relax permit or inspection requirements. What changes is how the walking surface attaches to joists that already meet structural rules.

Watch for: Marketing language that treats composite as “low maintenance so the build is simpler.” Maintenance is about the surface. Collapse risk still lives at the ledger and the guards.

Acclimation and job-site handling

Boards stored in full sun on one side and shade on the other will not behave the same length at install. Competent crews stage packs flat, off the ground, and install within the temperature range the manufacturer allows. Cutting produces polymer dust; clean cuts and manufacturer-approved blades matter more than they do with softwood.

Watch for: Boards stacked in a twisted pile in the driveway for a week, then forced flat with fasteners. Those boards will still try to return to the shape they held in storage.

Hidden clips versus face screws

Most modern composite systems use a groove-and-clip or similar hidden fastener so the face stays clean. Clips only work when the groove, the clip model and the joist spacing all match that product line. Face-screwing a “universal” screw through the board face may void the finish warranty even if the board holds.

Watch for: A crew substituting a cheaper clip or wood screw “because it holds.” Ask which fastener SKU is listed for your exact product and colour line.

Gapping for expansion and drainage

Composite expands and contracts with temperature more than dry hardwood. End gaps, butt joints and the space against the house wall are set from the manufacturer’s temperature chart for the day of install — not from a single fixed gap used on every job. Side-to-side spacing also drains water; pinching boards tight for a seamless look traps moisture on the joists.

Watch for: Boards butted tight end-to-end in summer heat, or gapped like green pressure-treated lumber in winter. Both patterns show up later as buckling or as gaps that look like missing pieces.

Stairs, picture frames and breakers

Stair treads, riser covers, fascia and border boards often use different profiles from the field decking. Colour matching across those pieces is a ordering problem, not a sanding problem — composite does not sand out a mismatch the way paint can. Plan the border layout so rip cuts fall where the manufacturer allows them.

Watch for: Field boards used as stair treads when the product line requires a specific tread profile, or fascia screwed only into the board ends with no solid backing.

Inspection, registration and the two warranties

Framing and final inspections still close the permit. Separately, composite surface warranties almost always require product registration and proof of correct fastening. Labour to replace a failed board is rarely in the manufacturer document — that is the builder’s workmanship warranty, if any.

Watch for: A handover with no registration receipt and no written labour warranty. When a board fails in year four, you need both documents.