Hi, I've spent the last few days trawling through dozens of posts and now my head is spinning with the amount of differing information I've read on what is a fairly common subject.

I am planning on laying a ground-level deck which will be part laid on concrete and part laid on earth. The area above the concrete is pretty straightforward and all the info I've read seems to point me in generally the same direction but when it comes to decking over the soil I'm getting a bit confuzzled.

The concrete is approx 90mm below where I want the deck to finish so I plan to simply lay appropriately sized TP across at standard spacings. The soil level is vaguely at the same level as the concrete but has the usual obvious undulations etc. While it seems apparent that using 70x45 on the concrete will be more than adequate, I'm pretty sure it's nowhere near adequate over the soil.

Obviously, with the soil and concrete being at similar levels, I'm assuming I'm going to have to do a fair bit of shovel work to accomodate the correct sized timbers but this is where I'm stuck. I've read that I can use 140x45 buried in soil with the deck laid directly on top, I've read that I'd need bearers set on stirrups in concrete footings and joists above, I've read that I can use varying sizes of timber laid on concrete pads or pavers, I've read that people have laid a new slab to match the old and then lay timbers across this - the list seems to go on. I wish I'd stopped reading a few hours ago as soon as I read the first post but I didn't and now I'm more confused than when I started.

I've attached a drawing of the basic layout of the deck showing the general layout. I've indicated the basic layout of the joists as this is about the only thing I've got consistant agreement on - I've put them at approx 400 centres with some slight variance to allow for a couple of posts I need to avoid. Obviously, with some 24 joists to be laid across the soil I've got a fair bit of earth to move so don't want to be digging any more than is necessary. My budget won't extend to any form of mechanical help so it's just a trusty shovel for me.

Could one of you experienced folk out there give me the benefit of your knowledge and give me your opinions on the most suitable way to go about laying the timbers across this area as I'm going cross eyed after staring at my screen for so long!

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Mate your right plenty of options .. berrying 140x45 aint one though as you would have to get sleepers that size to get the appropriate treatment for in ground use

If your putting timber on or in ground it has to be h4 or h5 treated

option 1 pull uout the turf for the area of the deck and extend the concrete and batten over and deck

option 2 dig out enough dirt to put your 90mm joist at the right height and get a 90 x 70 bearer under the joist and still off the dirt to support the joists .. support bearer on a stirrup set in concrete

option 3 dig a trench and lay treated sleepers in at the appropriate heght to act as bearers for the joist to sit on.. joists need to be off the soil and sleepers should be set on road base or concrete


option 3 is the cheapest but not a method we use

utemad

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www.dialadeck.com.au

Thanks for the response. It's made things a little clearer for me and I guess I'll go with option two - it seems to be the more 'standard' approach.

Can I now ask to clarify a couple more points for me?

Firstly, if I use 90x90 bearers supported on stirrups, what is the max spacing between the stirrups? I've read of people using 1000mm, 1200mm, 1500mm but can't seem to find any details of what the 'actual' max is.

And secondly, is 1300mm centres on my bearers OK for running 90x45 joists as this allows me to run three bearers across the soil section?

Thanks in advance for any advice.

What are the planning regs re the size of the deck and if you need to have it complying does your plan comply. (normally over 25m2)

Not being a spoil sport here but things can bite you later particularly at sale time.

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Mate if you pull the bearers in 200mm from the front and 200mm from the slab then you'll reduce your centres a bit.. 1200 is nice between bearers for 90 x 45 joists
So joist span would be 1200

1300 between shoes along the bearer is as far as you would want to go to avoid bounce

A lot of tables don't have spans for these sectional sizes but for treated pine this is what we have found from experence

utemad

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www.dialadeck.com.au

Thanks for the input UteMad.

Pulling them that bit closer isn't an option really as I'd already dragged them in a bit to get the 1300. Looks like I'll have to either add an extra bearer row or up the size of the joists - just have to figure out which is the most cost effective option.