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How to build footing-free decking?

Andrew7
New Contributor

How to build footing-free decking?

Hi everyone, new member, just moved into my first house and experiencing the fun of DIY.

 

I'm building a deck out the back door and am trying to work out what footings to use and then found the footing free option.  I'm concerned that if I build too close to the house or connect decking to the house I will void my warranty with the builder.  Footing free seems like a good idea if I can make it solid enough that it won't move.

 

I saw the post that talks about footing free bearers: https://www.workshop.bunnings.com.au/t5/How-To/How-to-build-a-low-level-deck/ba-p/45715

 

My questions are:

a) I have H2 type soil, is this an issue, can I still use this method to build footing free?

b) The previous post talks about H5 timber, can I swap this out for aluminium bearers?

c) Is there a product recommendation for the membrane?

d) I have crusher dust for the compacted soil, what depth does it need to be after compaction?

e) How do I ensure there is no water building up on the higher side of the bearer while still keeping my decking level?

 

Screen Shot 2022-05-18 at 8.00.20 am.png

 

Thanks!

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to build footing-free decking?

Hello @Andrew7

 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thank you for sharing your questions about your low-level deck.

 

Let me try and answer some of your questions:

 

  • H2 soil is generally classified as a highly reactive clayey soil that's between wettish and dryish soil, moisture conditions can produce very high ground movement. In numbers: 60mm to 75mm of vertical movement. If these are the conditions in your area I'm afraid that it is not ideal to be doing the footing free option for your deck.
     
  • Ideally, you want to use materials that are protected against insect and termite infestation. Using aluminium is a good option, you'll need to refer to an aluminium span table in order to get the right size and thickness.  
     
  • Grunt 2 x 5m Black 200um Ultra Tough Plastic Film is commonly used as a moisture barrier. 
     
  • Compacted sand and gravel base are able to carry a great deal of load. The thickness of the base will depend on the size of your deck and the estimated load it will carry. This will include not only the weight of the deck but the weight of the number of people that will be standing on the deck at any one time. 
     
  • Drainage is critical when building a deck, it's important that the bottom of your deck has adequate facilities to remove water away from your deck. I suggest building a slight slope into the ground so that it directs the water towards a drain channel.   

 

It's great that you've seen the guide to how to build a low-level deck by @Adam_W. Before going any further, I recommend visiting your local council and having a look at the rules and regulations when building a low-level deck on open ground near your house. We definitely don't want to void your warranty with the builder. Some states require that you place a gap between your deck and the house others require a termite barrier, it all depends on what the rules are.

 

Would it be possible for you to post a photo of the area where you plan on building your deck? Can you please also include what your proposed deck size will be? Our members can then assess the conditions in the area. We can then make recommendations on the best possible course of action.  

 

Bunnings has created a new seven-part series on how to build a deck, starting with how to plan out your deck. The series includes:

 

 

Here are some more amazing decking resources:

 

If you have any other questions we can help with, please let us know.

 

Eric

 

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Andrew7
New Contributor

Re: How to build footing-free decking?

Thanks for the feedback it is very helpful for a beginner.

 

For context this is where I am up to at the moment:

 

The plan is to fill the back yard 50mm below the slab height and then lay turf on top taking the lawn to slab height (about 50 cubic meters in total).

 

Under where the decking is going I have needed to fill this so that any water will not sit under the decking and become a pool.  To do this I have put in Crusher Dust with the plan to compact it sloping away from the house.

 

Have a put in about 150mm deep of crusher dust currently:

 

 

 

281907343_345105854219616_7434179622243325803_n.jpg  280356451_984282562124827_3115237699528489497_n.jpg

 

Leaving me about 150mm to work out the decking (height of bricks).

280040359_374885048021027_7307387285895409946_n.jpg

 

Dimensions for the decking is about 8000x3000mm.

 

So as to not void the warranty of the house I don't want to connect the decking to the brickwork and will leave 10-20mm gap for termite inspections etc.

 

Close to the house I'm not sure how to go about setting up the posts / bearer supports.

 

At the end & on the sides I can do Posts at 400mm deep x 300mm wide (I think thats right?)

Actually, here is a drawing I think explains it:

 

281506526_737986047198170_729874689838075140_n.jpg

 

So the unknown for me is what to use along the house?

 

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: How to build footing-free decking?

Hi @Andrew7,

 

You can still concrete in posts next to the house. Set them back far enough away from the wall to create your footer. The deck portion along the wall can then be counter-levered between the last footer and the house. I've created a rendering for you below to illustrate it better.

 

Depending on the size of the timbers you're using for the structure, you might need more support than what you've featured. Typically, 90 x 45mm pine shouldn't span more than 1000mm, and you're spanning 1500mm. Just something to consider.

 

Please let me know if you have any questions.

 

Mitchell

 

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Re: How to build footing-free decking?

Thanks @MitchellMc 

 

I've been reviewing the diagram and decided that the design I am aiming for won't work with that solution so I will need to attach the ledge to the house. 

 

I'll be taking precautions to ensure the termite barrier is visible for inspections and there is a gap between treated timber and the home.  

 

I'll be starting on the outer edge posts to frame the area tomorrow, I'll post the progress as I go.

 

Thanks!

 

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