Composite decking calculator
Composite is the most quoted deck and the most argued-over price. Enter your size, pick composite, and see the boards, the closer frame it needs, the fixings and the cut list — in 3D, in metres or feet. No national averages: the cost appears only when you add your own supplier rates.
What changes when the deck is composite
Closer joists than softwood
Composite boards are less stiff across a span, so the frame carries more joists for the same area. The calculator applies the spacing for your country and shows it in the checks, which is the line most hand-written lists miss.
Board widths differ by range
A composite board is rarely the same width as a softwood one, so the row count changes. You can set the board width and the gap by hand in Fine-tune when your range is different.
Fixings are not nails
Hidden clips or colour-matched screws are counted per board metre, not guessed as a bag, so the fixings line matches the boards you are buying.
Expansion gaps matter
Composite moves with temperature. The gap you set feeds the board count and the cut list, so the ordered lengths already allow for it.
Why composite quotes come in high
A quote is not the board price times the area. It carries the frame, footings, fixings, waste from stock lengths, labour, your margin and tax. Online calculators that return one tidy number usually leave most of that out, which is why homeowners are shocked by the real figure. Here the quantities are shown line by line, and the money only appears with rates you entered, so a builder can defend every line of it.
Quoting composite jobs?
Save your rates once, then print a quote with your company name, your labour and your margin — from the same take-off the client saw in 3D.
See the plans