Decking sub-structure best practice

[NeilScotland]

I'm starting a decking project in the spring (Keen DIY'er)  and so I'll have many questions to come... but, the first questions I have are about which type of structure to use. And are my spans ok?

There is an absolute mountain of information out there about what is the best way to do this, it's quite over-whelming - but, from what I can see, there are two distinct differences in the base structure.

And I'm not sure what is best for my own effort....

 

1. Build a frame, put your joists in the frame, attach the frame to the support posts that you put in the ground.

2. Put supports in ground. Add some bearers. Place the joists on top of these bearers. (this requires more digging).

 

Is there a right way or a wrong way of these options?

 

I've drawn out a plan (Note: noggins to be added), based on all that I've seen - and it takes option 2 above. It's a hard wood deck and my decking boards will likely be 21-25mm (I will have them milled - was thinking 25mm). 

I'd appreciate any help on the best way forward and if the spans seem ok.

 

I found this document to help: https://www.trada.co.uk/.../3809/design_a_deck_planning.pdf

 

I was just going to get standard 2x6 for the sub-structure. (i'm in Amsterdam but the materials are largely similar to UK). 

thanks

Neil 

[Mr Punter]

Don't sink the support posts into the ground, just create concrete pads and use galvanised post bases.  This will stop the posts rotting.

[NeilScotland]

4 minutes ago, Mr Punter said:

Don't sink the support posts into the ground, just create concrete pads and use galvanised post bases.  This will stop the posts rotting.

Thanks - what specs would you use for the concrete pads?

 

neil 

[Mr Punter]

Depends on the ground.  You need to dig out the soft topsoil until you reach firm ground.  Maybe 300-450 square.  Concrete 150mm thick min according to your finish levels.  You don't want the deck to be wobbly but neither are you going to drive over it.