Decking spacing

[Chumley]

Most sources I've come across say gaps between decking should be 3 to 4 mm. I'm thinking in particular of treated pine decking (but I guess I could ask the same question for hardwood), is there any reason why the gaps shouldn't be larger, say up to 15 mm?

Curiously,
Adam

[silentC]

Do you mean legal reason or practical?

The only regulation I'm aware of is that decking in a bushfire zone is minimum 5mm spacing. I'm unaware of any maximum.

However, if you make the gap too wide, it might be impractical, depending on the situation. Thinking of the following:

1. Pets might find it difficult to walk on
2. More things can fall through the cracks - ie. car keys, money, important stuff like that
3. High heel shoes could be tricky
4. You can see what's under it more clearly - ie. the ground underneath, sub-floor timbers etc.

So maybe we should ask why you want gaps that wide?

[Chumley]

Actually I meant practical -- I've given up on legal, no matter how much research I do I always seem to find out something new after I've done it...

The reason. Yes, well, I've got a hexagonal gazebo to cover with decking. The floor has joists running front to back (from the entrance) as I wanted the flooring to run side-to-side. But there is a central bearer running left-to-right in the very middle of the floor.

Now I don't want to have a gap in the flooring over this bearer 'cos water would get trapped, so I need to put one floorboard over the bearer. I also want a full floorboard at the front with a 10mm overhang. Then I can fill the space between with boards. I have some play because the bearer is 50mm wide but the floorboards will be 90mm. However, I may not be able to juggle them to give me only a 3 or 4mm gap. I suppose I could find out the exact distance and do some calculations and trim all the boards, but I'd like to avoid that if I can.

Cheers,
Adam

[silentC]

I'd be surprised if you can't work it with smaller gaps than 15mm though. If you think about it, you only need to gain 10mm from 9 boards to be able to fit in a 10th. So if you had 9 boards spaced at 15mm you can fit in another one with a 5mm gap between each by reducing the gap between all of them by 10mm. Given that 10 boards cover about 945mm with a 5mm gap, and I'm sure your floor is wider than that, I'm sure it will work out better than you think.

[silentC]

Say your floor is 2000mm wide. 21 boards will cover 1990mm with a 5mm gap between each: 21x90 + 20x5 = 1990. So you need to make up 10mm. If you increase the gap to 5.5mm, you'll get there. Conveniently, that would give you a board in the middle.

If it worked out to an even number of boards at 5mm spacing over a similar distance, the maximum you'd need to shrink or grow to have an odd number would be 90mm. So if you adjust the gap to either 3mm or 7mm, over 20 boards or so, you'd be getting close. Even 7mm is better than 15, although it's a bit on the wide side and I'd be trying to squeeze another board in, rather than have big gaps like that.

[Chumley]

You're pretty good value - whatever they pay you should be doubled.
I obviously hadn't thought it through properly.
Thanks for the tip,
Adam

[Bleedin Thumb]

You haven't got the bill yet!