Ground decking

[cihan]

I want to build a deck that is close contact with the ground, am i able to use H4 sleepers as for my bearers? I read and it says H4 timber is not for structural purposes?

[MitchellMc]

Welcome to the Bunnings Workshop community @cihan. It's great to have you join us and many thanks for your question.

Treated pine sleepers are used for retaining walls and not for weight-bearing applications in construction. They do not have a structural rating and that is why they state not for structural purposes. The appropriate timber to use when building a deck in close proximity to the ground is H4 treated and F7 structurally rated. In our range that would limit the selection to post sizes.

How close are your bearers going to be to the ground?

Mitchell

[cihan]

Backyard decking: Some parts of the decking will be almost in contact with the ground due to matching the same height of the existing structure. As you mentioned H4 treated F7 timber is for posts. So the question is: Is there any structural timber available in the market that can he used on the ground as a bearer.
 
Second question is 100x50 H4 Sleepers have higher density and better Second moment of inertia right (I=bh3/12) than 90x45 H3 timber. Both are treated right? So please tell me what are the structural differences? What are the bending strength of those for comparison? What are the max span for those two? 

Worst case scenario if H3 timber preserved with “eco in-ground timber protects” (from Bunnings) will it work? But this will be last option. 

Sorry for to many question but I really want to know further.

[MitchellMc]

@cihan,

We do not stock any H4 timber which has a structural rating and is suitable to be used as bearers. I have not heard of structural rated H4 being available but I am sure someone would make a specialised product if you looked around.

According to the Building Code of Australia, any timber used in construction that bears weight needs to be structurally rated. Our treated pine sleepers have not had a structural assessment done on them as they are not traditionally used in weight-bearing applications. You can find the max span for the 90 x 45mm H3 F7 in relevant timber spans tables available online. You will not find what the max span is for H4 sleepers as they haven't been graded for structural use.

I can't clarify if H3 timber coated in Diggers Eco In-Ground Timber Protecta will be suitable for your application. Though applying the product on H3 timber will most certainly extend the timbers lifetime. 

Mitchell