How to build a ground-level deck?

[MMason]

Hi

Looking through the AS 1684.3 for building a ground level deck. 

All the bearers listed in Table 5 Floor bearers, Supporting floor loads only. Table five was recommended in one of the many deck building design guides I have read. 

There using two boards bolted together for all bearers. There is no option for single boards at a larger size to manage the load. 

looking at YouTube videos where professionals are installing ground level decks.  They all seem to use only one board as a bearer. 

So I can get a cantilever at one end, from table 5, I need two 190mm x 45 timbers bolted together.

I picked this size as to get a 900 mm cantilever and a 3 metre spacing. 

Is this correct or am I missing something here by having to bolt two boards together. 

[MitchellMc]

Welcome to the Bunnings Workshop community @MMason. It's fantastic to have you join us and many thanks for your question about building a ground-level deck.

While I don't have direct access to AS 1684.3, I understand your concern about needing two 190 x 45mm timbers bolted together for the cantilever. A cantilever of 900mm is indeed quite large, and it's not surprising that the design guide would specify two laminated timbers to achieve the necessary strength and stability. Using two boards bolted together can be an option to achieve a span without resorting to a single, much larger timber. 

You may have seen single bearers in some YouTube videos, but these may be for different spans, loads, or designs, which don't require the same level of structural support. It's always important to follow the specific requirements of your build, especially with a cantilever of this size.

For any critical structural elements, like your cantilever, I'd recommend verifying your interpretation of the construction codes with an engineer or builder to ensure the safety and integrity of your deck.

Please feel free to ask if you have any more questions.

Mitchell
 

[MMason]

Thanks Mitchell

The AS tables suggest two bearers bolted together even if I wasn't  incorporating a cantilever. 

I was just down at the local Bunnings, they were suggesting the contractors that they supply to, only ever use one beam not two bolted together. 

This is where I would like confirmation of the general practise for bearers sizes. 

Also can you tell what the grade of the H3 treated pine that bunnings sells. Is F7 or MGP10. 

 

[EricL]

Hello @MMason 

I can only suggest what the AS table recommends. I propose engaging the services of an engineer or builder and presenting to them your idea of using a single beam in your decking plans. 

In regards to the framing timber Bunnings sells they are MGP10. But you'll also find that we sell F7 treated pine primed LOSP. I suggest having a look at the Bunnings website and typing in the timber size you're after. The product details are further down the webpage.  

If you need further assistance, please let us know.

Eric