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Sawdust & Steel
project guide

Why Composite Deck Gaps Change With the Weather

Composite deck gaps depend on the board, fastener, and installation temperature. Check the actual product instructions before closing an uncomfortable-looking joint.

  • 2 min read
  • by Sawdust & Steel Workshop
Project Guide · Ontario homes · 2 minute readRead the 1 primary source

A neat deck photograph rarely includes a close-up of the gaps. Then November arrives, a joint looks wider, and suddenly that little space becomes the only thing you can see.

Identify the board before judging the gap

Trex explains temperature-sensitive spacing and directs installers to the applicable guide. Side spacing, end spacing, and clearance against a wall are different details. A measurement copied from another brand can be wrong for yours.

Keep the useful space useful

Photograph the same joint with a ruler and note the weather. Record whether it is simply wider or whether an end is lifting, rubbing, or losing support. Those are different observations. Do not fill the joint with caulk or force boards together to improve a winter photograph; drainage and movement still need somewhere to happen.

Before the next step

  • Find the exact board line and installation guide.
  • Compare joint type and installation temperature, not appearance alone.
  • Have unsupported, buckled, or loose ends inspected.

A deck is allowed to move. Your installation should have a deliberate way to accommodate it. Ask for that explanation before asking for a smaller gap.