Timber or composite decking: what changes in the build?
The frame underneath is still timber. What changes is joist spacing, fixings and how you cut.
Both decks sit on the same treated timber frame: posts, beams and joists. The board on top is the difference, and it changes more of the order than people expect.
Many composite boards ask for joists closer together than a softwood board would, often 300 mm or 12 in centres, and closer again on stairs or diagonal runs. Closer joists means more joists, more hangers and more screws.
Composite usually goes down with hidden clips and its own screws, and needs a gap at board ends that changes with temperature. Timber is face-screwed and can be planed or sanded later. Composite can't be fixed that way once it's marked.
Check before you buy or dig
- Read the joist spacing in the installation guide of the exact board you'll buy, before you build the frame.
- Order the clips and start/end fixings made for that board range. They are not interchangeable between brands.
- Composite boards are heavy and long. Check delivery access and stock lengths before you set the deck size.
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Compare the take-off for both in 3DA general answer, not a structural design. Local rules, ground and loads decide the final build.