Hi
I'm assuming that when you say "all timber will be hardwood", the supports will be F15 hard wood? I was just going to mention that unless you are getting red gum (which costs a squillion), hardwood is mixed. What you end up getting is timber that has the same lifespan as treated pine, plus the hassles of installing decking on hardwood. So a lot of timber merchants I have talked to either avoid stocking hardwood and/or insist on treated pine.
Either way, below you will see is AS1684 with F5/F7 specs. The supports are rightsized to AS requirements which should give you a comparison and cost. Similar to Stevoh, I would go 90x90. I would also consider 5mm gap not 3mm.
Timber Requirements |
Bearer - 2 x 140x45 F5 TP laminated, 60mtrs @ $5.85 Cost $351 |
Joist - 140x45 F5 TP at 428.6mm centres, 129.9mtrs @ $5.85 Cost $759.915 |
Decking - 90x19mm wide board with 5mm gap, 602mtrs (incl 10% waste) @ $4.85 Cost $2919.7 |
Total Timber Cost $4030.615 |
|
Screw and Support Cost |
Decking Screws - 50mm 10g screws 2 per joist, 6 boxes of 500 @ $60 Cost $360 |
Supports - 300x90 Stirrups, 20 stirrups @ $8 Cost $160 |
Concrete - 0.92m3 concrete delivered, 0.92 m3 @ $340 Cost $312.48 |
Total Support Cost $832.48 |
|
Total Project Cost $4863.09 |
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Support Detail |
Bearers - 5 with a bearer span of 1800mm supported by 300x90 Stirrups |
Joists - 15 spaced at 428.5mm centers |
Concrete - 20 holes 300x650 wide and deep |