New Deck : So many questions...

Ok this is my first time here and also only my second major home project. The first was a post and rail colorbond fence which is still standing a year later :)

I'm planning on building a ground-level deck, 11 m x 6 m behind my house. The house is L shaped, and there's a rather large tree in the backyard which will overshadow most of the deck. Said tree is also the reason why the current pavers are no longer level - which is why we are going for a deck instead of paving or concrete :)

I using Jarrah for the decking, I managed to get 1500m of 65x20 pencil-round for about $1.10 / metre from a local auction place. The framing is all 190x45 CCA pine, with a ledger along the long side of the house, and two doubled 190x45 beams at 2.6 and 5.2 metres. The joists are all 190x45, hung from the ledger and resting on top of the beams.

Because the deck is so low (I need to excavate a little to maintain a minimum 300mm clearance for airflow), I want to go post-less, using Formatube cardboard tubes to build concrete columns right up to the beam level, with galv. stirrups connecting the beam to the concrete.

Biggest question is - Are these forms available ANYWHERE in South Australia? Best quote I've got is from FormaTube in Melbourne, and they want $400 including freight for 12 metres of 305mm tube, which sounds a lot for a bunch of cardboard.

I've specified 300mm diameter footings (600mm min. depth) in the plans that have already been approved, but I'm wondering if this is overkill too?

I'm a newbie at woodworking but I'd also appreciate any pointers on the best way to tackle this. Would also appreciate any tips on where to buy supplies in Adelaide, other than being gouged at the local Bunnings!

Thanks

Steve

The formatube is not necessary....

All you need is to finish your footings at a smidge above ground level ground level (your footing spec is overkill for most parts of Oz - but fine for Adelaide) then bolt down some Pryda half stirrup post anchors http://www.pryda.com.au/catalog.php?sectionid=20&type=Post%20Anchors&conn=PAH130 (which you can buy at Bunnings!!)

If you need to make them shorter than what they are....finish your footing below ground level (at the right height to give you the final stirrup height you need) then bolt in the stirrup....and fill the rest of the footing with concrete so that the post anchor is now embedded.

Or simply stick a length of 75x75 galvanised steel RHS in the footing with the concrete then bolt your beams to that....

So do the half-stirrups just bolt into the top of the concrete with Dyna bolts or something? Or can I set them into the footing itself?

To make the levelling easier, I'm considering building the beam, suspending it over the holes with the anchors already bolted in, and then just filling the holes - which I can only do if I set them into the concrete.. except this will make filling the holes harder - access to the site is already limited and I'd like to get pre-mixed concrete in (0.7 m^3) and do it quickly.


I guess I've just answered my own question - use bolt-in stirrups :)

Some stirrups are desigend to go into the footing. you rsuggestion is a valid method of construction.

If you excaveate as suggested is tahat going to create a puddle?

The tree (its a large variegated fig) actually stops most of the rain. But part of the excavation is a slight fall down a channel running along the middle with ag-pipe running out to the stormwater drain :)