Low level deck, where to start

[aaronwier]

Hi everyone, looking after some help with decking. We have a split level home with an outdoot section that was I believe used sit a spa. The tiling looked horrible, was raised in some parts, so I wanted to rip it up curious to see what was underneath so I could look at options. It appears to be big sections of sandstone, which they tiled over. The section is boxed in with brickwork. The high side of the brickword does seem very sturdy, though does look rough

This would be a great spot for a deck. Area is approx 3.5 x 3.5 with a view to extend out further in the future. 

My questions/comments:

• Where do I start? I know the area to deck, how do I work out the bearers/joists required, and relevant sizes?
• I'm not a complete noob, as I have built retaining walls, fences etc many times, and would love to give this a go
• Any considerations I need to take into account because of the sandstone? ie for footings? It varies in depth from 300mm to 600 or so. Can I use stirrups for bearers?
• Does the deck need to be attached to the house? As you can see from the pic, there is a section of  the house, but that wall is not flat all the way across (its like a render/textured paint)

Pics below:

I've read a heap of the low level deck posts here, which have been awesome. 

Thanks all

Aaron

[Jason]

Great to see you've found other low-level deck posts @aaronwier, it's certainly a popular topic on the site.

Let me tag the ever-helpful @ProjectPete who might like to kick off this discussion for you. 

Jason

[aaronwier]

Guess this is a tricky one no replies 🙁

[Jason]

Sorry about the lack of replies so far @aaronwier.

Let me tag a few other members for you who might like to share their thoughts on tackling the project. @Adam_W, @MitchellM, @Brad, @pete_brig, @Harv, @Crash76, @raymao268 

Jason

[MitchellM]

@aaronwier is that sandstone of just disintegrated old concrete?

This webpage should answer most of your questions https://www.bunnings.com.au/diy-advice/outdoor/decking/how-to-build-a-deck?gclsrc=aw.ds&&gclid=Cj0KC... 

I have never built a deck on concrete, but there are a range of low profile mounting stirrups available at Bunnings.

You may want to chemically anchour some Reo bar into the slab approx 200mm deep instead of using 100mm dynabolt for them though.

That looks like the powdery concrete which is just going to crack and turn into dust when you drill into it though.

I hope others with more knowledge will join in soon for you.

[aaronwier]

Thanks @MitchellM 

The surface is sandy but hard. Can be broken up pretty easily though.

[MitchellM]

@aaronwier perhaps try some test hole in it to see how structurally sound it is.

[Adam_W · Accepted solution]

An old handyman DIY technique for a small slab was to create a boxed-in area with bricks & then just fill it, or sometimes just skim coat over rubble, with a sand & cement mix. Quite serviceable but not overly strong.
I'm thinking this could be good situation for the Good Times decking system.

You don't have to use their decking but the adjustable supports and sub-frames could make it a lot easier & certainly easier to add on to further down the track.

[aaronwier]

Thanks @Adam_W i think you are spot on. It is indeed boxed in using bricks. I’ll have a bit of a dig anyhow and see how far it goes down. 

Are thinking of putting a spa here so might end up being concrete slab with decking around the spa and extended out too.

Will keep you all posted!