How many decking boards do you need?
Three steps. Divide the deck width by board width plus gap and round up for rows. Multiply by the run for lineal metres. Divide by board length with waste added. Our decking calculator shows a worked example, and this one only counts boards.
Which board length suits your deck?
Australian boards are mostly 5.4 m, with NewTechWood’s Avenue at 4.88 m and ModWood’s Marina at 4.2 m. A run of 5.4 m needs no cutting with a 5.4 m board. A run just over one board length, say 5.6 m, means a joint in every row; turning the boards the other way may be cheaper. Futurewood says boards over 3 m shouldn’t be butt joined.
Gaps change with temperature: a 5.4 m board needs 8.6 mm at 10 degrees, 5.4 mm at 25 and 2.2 mm at 40 on NewTechWood’s table.
See the boards table for each board’s size.
Questions
How many boards do I need?
Rows times run, divided by board length, plus waste. A 5 by 4 m deck with 137 mm boards needs 29 rows of 5 m, which is 145 lineal metres. Add 10 percent waste and divide by 5.4 m: 30 boards.
What waste allowance should I use?
Allow more for diagonal layouts and many cut-outs. The calculator lets you set the figure, and warns when offcuts can't be reused.