Composite Deck Board Spacing
Composite and PVC decking do not share one universal gap. Product line, fastener system and installation conditions determine the final spacing.
Open deck spacing calculator →Use the exact decking system, not a generic rule
Composite and PVC decking is manufactured, so the required side-to-side and end-to-end gaps are specified by the product maker. Hidden-fastener clips can also set the gap automatically. That means a spacing value that is correct for one product can be wrong for another.
The deck spacing calculator includes planning presets for common Trex and TimberTech cases and a manual mode for every other product. The manufacturer’s current installation guide always overrides a generic planning value.
Why calculate the layout after choosing the gap?
Once you know the required side-to-side gap, the calculator shows how many board rows fit across the deck, how many gaps occur, the linear footage and an estimated stock-board count. This helps avoid discovering an awkward last-row condition after most of the deck is already fastened.
End gaps, breaker boards, picture frames, joist support, heat exposure and specialty fastening details are outside the scope of the simple row calculation and should be checked separately.
Composite Deck Board Spacing FAQ
Is 1/8 inch correct for all composite decking?
No. Composite and PVC spacing depends on the exact product line and fastening system.
Does a hidden fastener determine spacing?
Many hidden-fastener systems establish a specific side-to-side gap, but you should verify the manufacturer instructions for the exact clip and board.
Can I enter my own product gap?
Yes. The Leftover deck spacing calculator has a manual mode so you can use the gap from your current installation guide.