To find deck board count: divide the deck width by the board width plus gap, then multiply by the number of boards needed to span the length. Always add 10% for end cuts and waste.
Common Deck Board Spacings
1/4" gap (6mm): Standard for pressure treated lumber — allows for expansion
1/8" gap (3mm): For composite decking or hardwoods like ipe
No gap: Butt joint — common with composite hidden fastener systems
Joist Spacing Guidelines
12" OC: For composite decking or spans over 12 ft — maximum rigidity
16" OC: Standard residential — works for most wood and composite products
24" OC: Only for specific composite brands rated for 24" spans
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