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How to build a low-level deck with 100mm clearance?

Hello experts

I am undertaking a decking project, a DIY. Low level deck with a ground clearance of 100mm or so. Attached is the proposed design.

Posts would be 400 mm length with 300mm underground.

Any suggestions or advice pls.

The bearers will be placed flat on the posts and the decking board on top.

Best regards

RaviDraft design

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Comments

JacobZ

Hi @jinugu,

Thank you for reaching out for some guidance with your decking project. I'm excited to help you out with this project.

As a starting point, I think you should have a read through How to understand deck components and How to understand deck span tables as they give all the information that needs to be considered when designing a deck.

I like to hear that you are going to use posts concreted into the ground. This will give you a nice sturdy deck that is well supported. When you say the posts are going to be 400mm in length with 300mm in the ground, are you saying there will be 100mm above the ground?

If so, you may need to rethink this because you can't sit a bearer directly on top of a post; it has to be attached to the side of the post using bolts. The standard is to have the post notched out so that the bearer sits on it with two bolts going through the bearer and post to lock it in place. This ensures the weight is supported by the posts, not the bolts.

Another thing to note is that Ekodeck must be supported every 450mm. If you are running the boards vertically between your bearers, they would span almost double this at 850mm. This would not be a safe deck.

My suggestion is to revisit your design and add some joists that run between the bearers. If you use 140x45mm framing timber, these joists can span up to 2600mm between bearers, meaning you would only need 3 runs of bearers. Something like this would work.

A design like this would ensure you are building your deck safely and suitably and are in line with the deck framing span tables and requirements of the Ekodeck.

Let me know what you think and if you have further quetsions, please don't hesitate to ask.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/53693#Comment_53693

Good morning Jacob Hope you had a good weekend.

Thanks for the reply.

Yes, the post would be concreted for about 300 mm in the ground and will stick out approx 100 mm above the ground

I take your advice.

Do you think it would be ok for the joists to be screwed into the bearers or will I have to use joist hangers. It would be easy for me to screw them in rather than using joist hangers.

Your help and advise is very much appreciated.

Thanks

Ravi

Best regards

Ravi

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/89085#Comment_89085

Hi @jinugu,

Joist hangers are specifically designed and tested to carry vertical and lateral loads. Screws alone, especially standard wood screws, are not load-rated and cannot safely transfer these forces.

To create a structural connection, you'll have to use joist hangers with these Pryda Timber Connector Screws.

Let me know if you have any further questions.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/110298#Comment_110298

Hi Jacob

Based out of your design, would the below work? I presume the spacing between joists is 450 mm.

As a side question, if I want a mimosa pergola of approx the same dimensions span the deck, how would you suggest i fix its legs?

90 x 22mm Decking H3 Treated

Best regards

Ravi

EricL

https://www.workshop.bunnings.com.au/discussion/comment/122512#Comment_122512

Hello @jinugu

I propose choosing your pergola first and making sure that its footing and installation are compliant with local council rules and regulations. This makes the pergola a self-standing structure that is not linked to the low-level deck. Once the pergola is in place you can then build the low-level deck underneath the pergola. Please make sure to check the rules and regulations in regards to deck height and pergola roof clearance.

If you need further assistance, please let us know.

Eric

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/130401#Comment_130401

Hi Eric

Thanks for the reply.

I was given to understand by a tradie that the pergola could be bolted to the same posts (800 mm under the ground) that I would use for the decking. From your advice, that's not recommended.

Do you recommend using concreted footings instead?

Best regards

Ravi

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/135311#Comment_135311

Hi Ravi, (@jinugu),

It is best to keep things separate, as permanent pergolas will often require submission of engineering plans to your local council, and the standard plans for pergolas will not take into account construction over an existing deck.

I would recommend doing some research on the type of footings your particular pergola requires. It will be dependent on the specific pergola you use, but concrete footings are common and likely a good option.

Let me know if you have any further questions.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/138575#Comment_138575

I was referring to this one, which is a semi permanent structure.. Mimosa 3 x 4m Lava Portsea Louvre Semi Permanent Gazebo - Bunnings Australia

Doesn't appear to require council's approval?

Best regards

Ravi

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/140759#Comment_140759

Hi Ravi (@jinugu),

It will depend on your local council's rules, but they often require council approval. We have copies of the engineering plans for these semi-permanent gazebos that we often send to our members.

In the engineering plans for that particular gazebo, it's noted that a cylindrical concrete pier underneath each post, 450mm in diameter and 600mm deep, is suitable for this gazebo.

If it was attached to a deck and you were required to submit plans for approval, you would need to have it reassessed by an engineer to ensure there is a suitable foundation. It would be much simpler to install the gazebo using separate foundations to the deck.

Let me know if you have any further questions.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/142368#Comment_142368

That was quick Jacob. Thanks

Are you able to share the plans/instruction manual for this product. I couldn't find any.

Regards

Ravi

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/143518#Comment_143518

Hi Ravi (@jinugu),

The instruction manual can be viewed here - Mimosa Portsea 3x4m Instruction Manual.

I have emailed you the plans, which would need to be submitted to the council if their rules require it.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/144389#Comment_144389

Thanks Jacob

Received with thanks.

I had another question but I will leave it for another day

Have a good weekend.

Best regards

Ravi

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/145021#Comment_145021

Hi Team

In continuation, I checked with the council and they connffirm that a consent is not required if the floor area is below 10 sqm. So, I am now looking at 3 x 3 mtr instead. On your comment below, quick set concrete alone is ok or does it require reinforced steel as well? I had a look at the designs you had forwarded, it doesn't have any reference to the use of reinforced steel.

Quote

In the engineering plans for that particular gazebo, it's noted that a cylindrical concrete pier underneath each post, 450mm in diameter and 600mm deep, is suitable for this gazebo.

Unquote

Best regards

Ravi

For the

Best regards

Ravi

EricL

https://www.workshop.bunnings.com.au/discussion/comment/145533#Comment_145533

Hello @jinugu

If the instructions have no mention of steel reinforcement, then it's ok not to put any in. But in saying that, if you wish to give your footing extra reinforcement then I would recommend putting in some Reo bars for support. In regards to the type of concrete, if you are not in a great hurry, I suggest using regular heavy-duty concrete as it provides an extra bit of strength. It will cure a bit longer, but you'll get a stronger footing.

If you need further assistance, please let us know.

Eric

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/53693#Comment_53693

Hi Jacob

Its been a while hope you are doing well.

What options have i got in case i am not able to notch the bearer on the post? I have seen elsewhere ( on the internet, professionals doing thatbearer and post) the bearers sitting on the posts direct. I understand its not recommended. But, if that was the only option i have got, would using angle bracket in conjuction with the use of T bracket work? as per the attached image. Ravi

EricL

https://www.workshop.bunnings.com.au/discussion/comment/90161#Comment_90161

Hello @jinugu

Yes, it is possible to use a nailing plate or large T plates to anchor the bearer to the post. Adding an angle bracket might add extra support. However, I still suggest doing a single lap joint on the post to hold the bearer in place as you can use a nut and bolt fixing which is much more reliable.

Let me tag @JacobZ just in case he wants to add more information.

If you need further assistance, please let us know.

Eric

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/143518#Comment_143518

Hello Jacob

Hope you are well.

I have managed to land myself in trouble.

For a external decking project (the posts in the chain), i have in error bought structural timber which i cannot return due to .log

Istics. Am I able to paint it to increase the life span? Which paint should I be using? I understand its not ideal to use untreated timber for external projects but I have no choice. Lifespan of 2 years is ok with me.

Best regards

Ravi

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/144434#Comment_144434

Hi Ravi (@jinugu),

Ultimately, returning and replacing the untreated timber with a suitable material would be much better, but if you have no other option, then 3 coats of Gripset Betta 4L Bitumen Rubber Waterproofing Membrane would give you the best chance of protecting the timber.

In saying this, I couldn't guarantee that the timber would last 2 years, even if it is coated in the membrane. If any moisture gets inside the timber, which it likely will because you need to use screws to attach decking boards, which will penetrate the membrane, then you might not even get 1 year out of it.

Considering the expense of building this deck, I would weigh the cost of returning the timber. If you contact your local store's Trade Desk, it might be possible for our delivery partners to deliver suitable replacement material and pick up the timber to be returned. You would need to pay additional shipping costs, but this is not necessarily impossible.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/145062#Comment_145062

Thanks Jacob. Much appreciated.

It should be fine to use it to use it on a concrete decking in a patio where there will be no water at all?

Best regards

Ravi

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/145552#Comment_145552

Just to add it's a covered patio

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/145552#Comment_145552

Hi @jinugu,

As long as the water stays out, you'll get better longevity, but there is also the risk that any water that does get in won't be able to dry out, as there will be little to no airflow.

Ultimately, it is not ideal, but if you coat the timber with bitumen membrane, you should be fine.

Jacob

jinugu

https://www.workshop.bunnings.com.au/discussion/comment/145933#Comment_145933

Hello Jacob it took a wee while but I managed to finish the decking on concreted patio. Photo is attached. I painted the bearers (untreated timber) with what you had suggested. Just the bearers near the sliding doors where water can seep in. There are openings and so I think no moisture will build up. Pic attached. Pls comment. Thanks for your help.

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/146237#Comment_146237

Hi @jinugu,

That looks great!

Thank you for sharing your finished product.

Jacob

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