# Forum Home Renovation Decking  Deck frame from steel

## DNL

I am thinking of building my 11mx5m deck from 50mm RHS and welding up the frame.  
I will price up the cost of steel vs wood vs Duragal for the frame. I am thinking that by using steel I would not need as many posts as well. 
Has anyone built a deck using steel? 
cheers

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## Bloss

My guess would be that your costs will skyrocket compared to timber-framed construction using RHS and you would need engineering design for any approval (to determine spans/ loads/ steel thickness etc.). 
Costs might be comparable if you use residential steel framing members like Quika-floor or FirmLok beams, but they are not available retail AFAIK usually through licensed supplier/ installers. See - http://www.lysaght.com/go/product/lysaght-quika-floor and http://www.lysaght.com/go/product/lysaght-firmlok-beam. 
Plenty of help and advice on here for timber . . . :2thumbsup:

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## DNL

Thanks Bloss  
I was thinking wood to begin with for ease of construction; however, my brother in law, who is a structural engineer and works with steel everyday has sold me on the idea of the RHS. I think it may take a tad longer - as I'm not as good a welder as the brother in law, but at the end of the day, I know I'll not have to replace any of the substrate. 
I've got a mate who is a chippy - he loves wood obviously and has limited knowledge of steel. The brother in law loves steel and has limited knowledge of wood. As it was just said to me, it is easier to weld a bit of steel on than add to a length of timber. 
Me....well I have no preference for either. It will come down to the tools, time and cost...plus the fact that the job in steel will improve my welding! 
With that said, I'm open to any advice for wood construction. 
cheers 
Dave

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## bpj1968

Using RHS lying down may allow water/moisture to accumlate and rust from the inside.
Using treated pine subfloor should last as long as the decking boards.

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## rod1949

Yep, I've built my deck using RHS duragal steel consisting of 150x50 bearers and 100x50 joists.  Its all straight and true not twisted or bent like timber is or will become and never have to worry about termites.

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## DNL

> Yep, I've built my deck using RHS duragal steel consisting of 150x50 bearers and 100x50 joists.  Its all straight and true not twisted or bent like timber is or will become and never have to worry about termites.

  Yep that is my thinking too Rod.  
Then deck will be around 600 off the ground at it highest point and around 400 at the lowest. Plus being under a verandah, the main part of the deck will be undercover with just the extremities exposed. 
Rod why did you go for the 150 and 100 x 50 bearers and joists? I would have thought 50x50 all round would be sufficient. Also how did you join to posts? I am thinking of welding a flat plate to the top of the posts and then welding bearers to that.  
Cheers

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## rod1949

> Rod why did you go for the 150 and 100 x 50 bearers and joists? I would have thought 50x50 all round would be sufficient. Also how did you join to posts? I am thinking of welding a flat plate to the top of the posts and then welding bearers to that.  
> Cheers

  
No No No 50x50 SHS, It would be like walking on a trampoline... springing everywhere. The steel framework members will still need to be of similar sizes as if it was done in timber. Talk to you Structural Engineer Brother in law and your Chippie mate.

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## Dan574

I would be going with whatever is cheaper, like rod said 50x50 shs would be no good, Im sure you wont find any span tables for steel rhs (unless you use firmlok or similar) thats why an engineer is engaged when steel is used they design it and tell you what to use for a given span. 
At least with timber span tables are easy to find, you will probably find that its cheaper as well.

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## UteMad

what about the added hassle fixing the boards down and the added cost of fixings.. nailing together has to be way quicker than stick welder.. If you time is worth anything timber will flog it for price the way your looking at regardless of whether it will be any good.. personally it will bounce using 50 x 50 and need more supports than a 6 x 2 joist.. Also using self drilling screws into shs will leave filings between the metal and the deck board and starting the rust 
utemad

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