# How much extra decking to order to allow for offcuts

I'm ordering decking for my deck and I'm wondering how much extra I should order to allow for the variation in length of the supplied decking? For example my deck is 4100 x 4500 and the decking timber is 90mm wide. So if all lengths of the decking timber were exactly 4500 I would need 207 lineal metres. Should I add 10% to this or 15%? The timber is being milled for me so it's important I order enough.

• I guess I would start by asking the mill how accurate they are going to be. There shouldn't be any variation in length or width that would make a 10 to 15% difference. That is a lot. Now, if you are doing a diagonal pattern or something other than straight it could add up to that. Apr 27, 2016 at 21:33
• The decking comes in variable lengths but the width of my deck is 4500mm and joists at 450mm spacing so I'm going to have to trim the lengths to fit. If I order the exact amount in lineal metres then I'm going to end up short. Apr 27, 2016 at 21:36
• Hmm yeah sounds similar to a tongue in groove floor. Maybe they have a rule of thumb for ordering that kind of flooring that would help you. Apr 27, 2016 at 21:45
• Ordinarily, I'd get 10% extra for a job like you describe. Given the custom setup, I'd seriously consider 15%, and maybe maybe if it wasn't outrageously cost-prohibitive, going for 20%. Splits, knots, and if you live in my world, mis-cuts happen. It would break my heart to have to go back for one more stick... Apr 28, 2016 at 1:03
• @AloysiusDefenestrate, good for an answer.... Do the 15% and consider 20% if the conditions are like you describe...
– Jack
Apr 28, 2016 at 3:00

Ordinarily, I'd get 10% extra for a job like you describe. Given the custom setup, I'd seriously consider 15%, and maybe maybe if it wasn't outrageously cost-prohibitive, going for 20%. Splits, knots, and if you live in my world, mis-cuts happen. It would break my heart to have to go back for one more stick...

Plus, if you get way too much, then you'll have the fun of figuring out a project on which to use the scrap. Bench seating? Table? Quadcopter? (Okay, maybe not the last...)