How to build outdoor BBQ framing?

[Paolo1]

Hi,

I'm building an outdoor bbq (on a concrete slab under a standalone steel pergola). The frame will be constructed with steel channel and will have a concrete benchtop (50-60mm thick). I would appreciate some advice on two questions.

Is the Siniat 75mm channel framing below adequate or should I use a heavier channel (ie. Stratco 75mm 1.2BMT)?

https://www.bunnings.com.au/siniat-76-x-3000mm-0-50bmt-steel-track-wall-siniat_p1091043

https://www.bunnings.com.au/siniat-76-x-2400mm-0-55bmt-steel-stud-wall_p1091176

Can I place the channel directly on the concrete? The area is covered, however the perimeter can get wet.

Any help would be appreciated.

Thanks

Paolo

[Jewelleryrescue]

Hi @Paolo1 

I like your thinking

But I don't recommend that steel under a heavy concrete BBQ top as that steel is not load bearing for one. For two that steel is galvanised but is not really ready for frequent immersions, you are better of using cut up aluminium posts braced diagonally or with supported fillet angle brackets in each corner as a direction change. the slab will need supports all the way under it as they are strong but brittle too, so more than just corner posts.

I would use brick work under your table slab as it is long lasting and can handle the weight and spread the load

Not what you wanted to hear but you don't want a cement slab collapsing down on you.

[Paolo1]

Thanks for the quick response. 
I’m not too concerned with the structural adequacy of the gal steel frame (if using the heavier 1.2mm thick). I was trying to be cheap and use a lighter section. 
However, I do agree with you about the channels being subjected to water. That bit worries me. Might think on it a bit more. Cheers 

[Jewelleryrescue]

Hi @Paolo1 

The steel you can always  spray paint additional layers of Galvanised paint over the surface as a second protection not just the factory coating . Cover especialy the cut edges that are exposed metal.

You  can  sit the steel on a10mm rubber mat strip so its out of pooling water longer, Little tricks like that.

I like coating the colourbond  fence posts with bitumous  paint for longer ground life.

Rememer to brace the steel  diagonally i use stainlesssteel  wire as used for  fencing applications.

Enjoy your project.

[Paolo1]

That’s for the info. Appreciate the help. Cheers. 

[MitchellMc]

Hi @Paolo1,

I agree with Jewelleryrescue's point that the Siniat channel framing is not structurally rated for such a heavy application as a concrete benchtop. The framing material you use needs to support the weight of the concrete slab, and the strength of the framing is critical in ensuring that the slab remains stable.

The width and length of the benchtop, along with the distance between support points, will determine how much structural support is needed. For shorter spans, reo-mesh within the concrete may provide sufficient reinforcement, but for longer spans, you would need to incorporate galvanised lintels or stronger structural elements to provide the necessary support and prevent failure.

Overall, I’d recommend reviewing the span and weight loads, and possibly consulting a structural engineer to ensure the design can handle the load safely and efficiently. 

Please let us know if you have any questions.

Mitchell

[Paolo1]

Hi @Jewelleryrescue ,

I have been watching way too many DIY BBQ videos, and noticed a lot of people using composite decking to raise galvanised frames off the concrete. Not sure if it rot over time? Another alternative could be galvanised or stainless levelling feet.

By the way I'm not using channel for the frame. I have decided to use 50mm galvanised SHS (2mm).

Cheers

Paolo

[Noyade]

Hi @Paolo1 

Can you provide a sketch of what you're attempting - with dimensions? And maybe a photo of where it's going.

How heavy do you think the concrete top will be?

Do you plan on welding the steel?

I was thinking of a welded frame with shelves - and wheels.

Would strong, large, lockable wheels fit in your plan?

Cheers!

[JacobZ]

Hi @Paolo1,

It sounds like an exciting project that I am happy to assist with.

Similarly to @Noyade, I'm not entirely sure what you are planning to do here. A sketch of the orientation would certainly help.

Composite decking is a combination of plastic and timber, so it would last for a good amount of time, but it will eventually rot if it is in direct contact with concrete.

I can't see a reason you would need to use composite decking to raise galvanised frames off the concrete as they are galvanised, meaning they are rust-protected and can be in contact with concrete.

Stainless steel levelling feet would take things to the next level in terms of rust protection, but I'm not 100% certain you would need it.

Let me know what you think.

Jacob

[Jewelleryrescue]

Hi Again   @Paolo1   

I hear you  re endless research 

Your 50mm Gal 2mm SHS steel  is a a great choice it will hold a car off the ground as long as it has  angled or  cross bracing.  The  Cement bench top slab will be supported.   Just make sure your frame  has supports in the middle region so the concrete dosnt try to bow 1mm and crack as steel will flex unsupported over time.     What if some one stands on the BBQ table thats another 50 to 150kg per person . Never say never lol

If you weld or cut the  steel use  some 

Dy-Mark 400g Silver Zinc MetalPro Primer / Top Coat   I/N: 1580764   $14^.48

It has the highest level of zinc in the  paint last  time  I  looked.  You  can paint a  color over the top.

It cant hurt to spray the whole steel frame  with Dymark as Gal steel is manufactured with a  minimal gal coating and will fail over time.  Unless it is the more expensive hot dipped gal that normally looks shiny.

Composite decking   as  stand off it will work for 20 plus years as a an estimate I dont know if it will like the 50 mm SHS putting alot of direct pressure like a  cookie cutter on it as the BBQ would  weight 200kg approx.  I would use a  paver cut in half as a guide as to strength.  But try the composite decking just need to jack the bbq up later if it fails to replace it. Placing a flat 5 mm aluminium flat bar 60mm x 60mm will help stop the cookie cutter action if it happens. Galvanised  metal  plate as an idea if you think that way others avaliable.

I think regular adjusted feet will not handle the weight Plus how do we attach them to the open 50mm tube of a  leg. A welded cap over the 50 mm leg with a drilled and threaded bolt hole is my first thought.  It will need a custom build I think to work.   But a  great   idea.  I prefer this to decking.  Maybe there are more robust industrial strength adjustable feet?  Other heavy duty adjustable feet are like $60 each.

If possible make the  BBQ base flat and level before you start or custom  cut the length of the individual legs so an uneven base will create a flat even  bbq top as differing leg sizes will be the easyest  solution.  Not like a concrete bbq top will be portable every day.

Hope  this  helps.