Poor planning
- Problem: Missing measurements and weak planning lead to wrong material orders and uneven construction.
- Solution: Measure accurately and use a deck board calculator to estimate the right amount of decking and screws. Make a detailed sketch of the deck before you start, and remember to add about 10 % cutting waste to the material estimate.
Weak foundations
- Problem: An uneven or unstable foundation can cause the deck to sink or go out of level over time.
- Solution: Prepare the ground properly with gravel or crushed stone for drainage, and use solid footings such as pier blocks or concrete foundations.
Wrong joist spacing
- Problem: Joists spaced too far apart cause deck boards to sag, bounce, or crack.
- Solution: Use 60 cm (24 in) on center as the standard, and 40 cm (16 in) for thin boards, diagonal installation, or composite — see what joist spacing should you use for a deck. Always check the manufacturer’s recommendations.
Poor deck board installation
- Problem: Screws that aren’t fastened properly, or boards laid without a drainage gap, lead to rot and cracking.
- Solution: Use stainless screws and keep a consistent 3–5 mm (about 1/8–3/16 in) gap between boards for drainage. Fasten the boards evenly and use spacer blocks for precision.
Insufficient finishing
- Problem: Many skip treating the wood after installation, which leads to rapid wear and damage.
- Solution: Apply high-quality oil, stain, or paint to protect the wood against the weather. Repeat the treatment annually for a long service life.
Bad drainage
- Problem: Missing drainage causes water to collect under the deck and creates moisture problems.
- Solution: Use draining materials under the deck and give the surface a slight slope to lead water away.
Neglected maintenance
- Problem: Many forget to maintain the deck after building it, which shortens its life.
- Solution: Plan regular cleaning, refinishing, and checks of screws and fasteners.
Use the deck calculator for better planning
To avoid these mistakes, use the deck calculator on this page. It estimates exactly how much decking and how many screws you need — typically 35–40 screws per m² (3–4 per sq ft) — so you can plan and build smarter.
Start planning today and build a deck that lasts for years!