Composite decking can lift the look of any outdoor area. But mistakes during installation can cost time and money. Worse, they can shorten the life of your deck.
If you’re building a new deck or upgrading an old one, here’s what to avoid.
Poor Planning of Joist Spacing
Composite boards need the right support underneath. If the joists are spaced too far apart, boards can bend or break over time.
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Stick to the manufacturer’s spacing guide. Most recommend joists at 300–400 mm centres for residential use.
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Use tighter spacing for diagonal layouts or heavier foot traffic.
Don’t guess. Measure twice.
Failing to Account for Expansion
Composite materials expand and contract with temperature changes. If you install boards too tightly, they can warp or buckle.
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Leave the recommended gaps between boards.
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Allow space at the ends for length changes through the seasons.
Have you thought about how your deck might move in summer and winter?
Laying Boards Without Slope
Flat decks can collect water. Water pooling will stain boards and speed up wear.
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Install a slight slope (at least 1–2 mm per metre) to help water run off.
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Check this with a level before you fasten down any boards.
Even a small slope makes a difference.
Skipping a Solid Base
The substructure holds everything together. If it’s unstable, your whole deck will shift over time.
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Use treated pine or steel framing rated for outdoor use.
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Make sure posts or footings are deep enough and set in concrete.
Soft or uneven soil? Use concrete piers or stirrups for extra support.
Using the Wrong Fasteners
Composite decking needs specific fasteners. Standard nails or screws can damage the material or void the warranty.
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Use stainless steel or coated screws made for composite boards.
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Choose hidden fasteners if you want a clean surface.
Fasteners also affect board movement and spacing. Are yours made for the job?
Not Checking Local Conditions
Salt air, heavy rain, or strong sun can all affect how your deck holds up.
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Choose products tested for your region.
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Use darker boards carefully in full sun—they get hotter underfoot.
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In coastal areas, go for materials with higher resistance to corrosion.
Local weather should shape your choices.
Rushing the Finish
Decks need time to settle. Rushing to place furniture or walk on it too soon can leave marks or disturb the boards.
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Let the deck settle for 24–48 hours after installation.
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Clean up sawdust and debris before it gets trapped.
Take a moment to check the whole build before calling it done.
Every outdoor space is different. Whether you’re building beside a pool or under a Bali hut, composite decking can work well—if it’s installed right. Avoiding these common mistakes will help you build something solid, safe, and good-looking for years to come.
