Joist spacing is it 450 c or 450 in and over

Was just wondering for 20mm Kiwla Decking when they say 450 is that from centre of joist to centre of joist or is that an in and over measurement a little confused?

Also someone told me that with kwila decking, not to used any spacings just butt them hard up against each other and in time they will shrink and form their own gaps? is this the way its done?

I have relayed some decking in the past and used spacer nails between boards, and with the spacer nails in place and have about 5 boards ready to be nailed I want to get a straight line of nailing but cant because the spacer nails are in the way to get a chalk line down the joist. Anyone has a different way of doing this?

450 is standard centre-centre measurement.

I always advocate spacing boards - even if a small gap - because it allows you to adjust if the run gets out of parallel as it aproaches the finishing end. Try a nail about 2½mm thick. Remember the gap also allows some air circulation...

A nice staggered pattern is easy if you eyeball either side of a stringline along the joist centre, or even make up a template and shallow drill the holes before laying. As a licensed contractor, I'd refuse to nail inline because I believe it predicates a greater risk of the joist splitting lengthways.

Regards, Adam.

Move the spacer nails, either to the edge of the joist or off the edge and let them hang there. A simple trick is to get a few bits of scrap or cardboard and put your spacer nails through these, to act as washers to stop the nails falling through the gap

If you're within a designated 'bushfire prone area' the minimum spacing is 5mm. Someone can correct me if this isn't Aust. wide.

Ditto in NSW.

I use wedges to gap mine and I tap them in a couple of inches beyond the joist so they're not in the way. It's part of a system though, so it probably wont work for you unless you do the 'lay every 5th board and fill in the gaps' method.

they are the same spacing 450 c to c or 450 in and over
les