Decking post spacings: is this enough

[James_H]

We are having a standalone garden deck built 4.5m long, 3.5m wide.

The frame has been constructed as follows. There are 100x100 posts. Joists from treated C24 '4x2' and 450mm spacing with noggins are screwed together and to the posts (no bearers). I have drawn it as below.

I thought that minimum post spacing was 1.8m, so I don't think there are enough, given the 2.25m gaps along the long edges and 3.5m on the right.

Fitter thinks this is enough and started on the deck boards. I'm not sure, not just for bounce but strength. For it to take the planned 180kg 4m x 3m pergola and the weight of people on it, should it have more?

Thanks all.

 

[Dereekoo]

timber size based on the post spacing way to small unless you are going to limit floor loading to some low value

 

[James_H]

That is my concern. Given the joists are in but posts could still be added, what post spacing would you recommend?

 

[Dereekoo]

That is my concern. Given the joists are in but posts could still be added, what post spacing would you recommend?

Layout based on total starter for ten loading of 150 kg/m2 as per domestic flooring, actual weight of flooring which is usually allowed for ignored but everything depends on what loading is used in design calcs, loading is more than would be normally expected on decking (whatever that is???). 50 x 100 bearer down centre of decking required to reduce spans of joists and keep deflection(bounce) within acceptable limits. Things can be designed to the nth degree but for simplicity of layout and the sake of 8 more posts ?????? Forget the noggins.

 

[James_H]

Thanks for adding that, I appreciate it. The joists and noggins are already in, but there is still time to dig for more posts between them.