The simple rule for decking screws
Running out of screws halfway through laying a deck is one of the most common DIY frustrations, and it is completely avoidable with a minute of maths. The basic rule is straightforward: you use two screws wherever a deck board crosses a joist. So the number of screws you need depends on how many boards you have and how many joists they cross. Work that out and you will buy the right quantity the first time, with a sensible few spare.
A quick worked example
Say your deck is 4 metres long and 3 metres wide, with joists spaced every 400mm. Boards run across the 3 metre width, so each board crosses about 11 joists along the 4 metre length. With two screws per joist crossing, that is roughly 22 screws per board. If your boards are 145mm wide, you need about 21 boards to cover 3 metres. Multiply it out: 21 boards times 22 screws is around 460 screws for the deck surface.
Rule of thumb: two screws per board at every joist. To estimate quickly, count your boards, multiply by the number of joists they cross, then double it, and add about 10 per cent spare.
Why add spares?
Always buy around ten per cent more than your calculation. You will drop a few, occasionally strip a head, and want some left over for repairs or a future addition. Screws are inexpensive compared with a wasted trip to buy more, and matching the exact same screw later can be surprisingly difficult once a batch sells out. A small surplus is cheap insurance against a stalled weekend.
Don't forget the substructure
The figures above cover the visible deck surface. If you are also building the frame, you will need additional fixings for the joists, bearers, and any connectors or brackets, and these are usually larger structural screws rather than decking screws. Factor those in separately so you order everything in one go.
Buying the right screws in the right quantity
Our decking screws are sold in boxes with the quantity clearly listed on each product, so you can match your total to the right pack size without guesswork. If you would like a hand sizing your order, or you are not sure which screw suits your boards, our team is happy to help; we would rather you ordered the right amount once than came back short. Browse the decking screws range to get started.
