Low-level deck over concrete

[Backyardtradie]

Building a low-level deck transformed the look of this outdoor entertaining area.

• The project
• Before and after
• How to build a low-level deck
• More inspiration for your deck

 

The project

I built a 3800 x 3440mm low-level deck on a concrete slab. The deck meets the house on two sides, with a 120mm clearance on one side and 110mm on the other, so I decided to keep the deck height just above 110mm.

I used 90 x 45 treated Pine joists sitting on galvanised brackets with about 10mm ground clearance. I was planning on using 70 x 45 joists, but MitchellMc suggested using 90 x 45 to stop the timber from flexing.

I ran the joists in the alternate direction to the decking boards with 400mm spacing on the joists to support the timber.

Pre-sanding.

Washed.

Oiled using Cutek with a matte finish.

Before and after

How to build a low-level deck

A low-level deck can pose a range of potential design and installation problems, with particular challenges around ventilation, drainage, termites and rotting. But it doesn't have to be a difficult project once you take the time to understand the basics of how they are put together.

Experienced Bunnings Workshop member Adam Woodhams has created a comprehensive guide to building your own low-level deck which should provide an excellent reference for getting started. 

More inspiration for your deck

Whether you are building a new deck or rejuvenating an existing one, get inspired by the clever and creative Bunnings Workshop community in our Top 10 most popular deck projects.

[cathham]

That looks great ! 

[MitchellMc]

Welcome to the Bunnings Workshop community @cathham. It's sensational that you've joined us, and wonderful to see you're excited about this project.

Let me mention @Backyardtradie so they are alerted to your kind comment.

Are you considering building a deck at your own home? Something like this project could really transform the feel of your whole outdoor area. Please let us know if you need any assistance, as our knowledgeable members would all be keen to provide any guidance you need.

We look forward to hearing all about your projects and plans around the house and garden and encourage you to let us know anytime you need help or have something to share. You'll find tonnes more inspiration within the community, just like this project, and I can highly recommend reading through our Top 10 most popular deck projects for more ideas.

It's great to have you on board.

Mitchell

[ssjolly]

Great outcome @Backyardtradie

I have a question. I was wondering how did you go about fixing the treated pine next to the wall? and which bolts and nuts did you use to attach the timber to the brackets?
Thanks

[Backyardtradie]

@ssjolly  Apologies for the delayed response. 

[Backyardtradie]

@ssjolly I had limitations with Hebel hence had to take the longer path as shown below. If you have Bricks- suggest pre-drilling through the wood and brick wall and using fasteners suggested by @MitchellMc . 

Reach out as you need- I am sure you'll have more questions when you progress with the project. 

Good Luck!!

[Beachbox]

Beautiful job!

[shez_89]

Hi @Backyardtradie @MitchellMc , 
A noob on this forum but I'm looking to build something very similar to what @Backyardtradie built. I've got an alfresco enclose on three sides. I'm planning to use 90x45 joists and bearers, and am looking to bolt the bearers to the brick walls. There's about a 10mm clearance once all joists and bearers will be installed although wondering if this will be enough (I noticed this being OK on a couple of other discussions). Do have a couple of questions:

* What screws should I use for the angle brackets of the joists to be bolted to the ground? Also, I know I case Dynabolts to bolt the bearers to the brick wall, although what is the recommended length of bolt give I'm using the 90x45.

*What screws should I use for the merbau to be screwed into the frame?

*Is there anything else I need to consider while building the deck? Pain points etc?

Cheers

Shez

[MitchellMc]

Welcome to the Bunnings Workshop community @shez_89. It's wonderful that you've joined us, and many thanks for your question on deck construction.

A 10mm gap under the timber is really the bare minimum. It might allow water to drain, but there will be limited to no airflow under the structure. Time will tell if this becomes an issue that could lead to a premature life span on the deck.  

If the ground is concrete, then Dynabolts are also used to fix the joist brackets to the ground. To join the brackets to the joists, you can use Zenith M10 x 40mm Hot Dipped Galvanised Hex Head Coach Screws. You need to space your ledger board off the brick wall, as it can't be placed directly onto the bricks. You can do that with 10mm worth of plastic packers or flashing. Your Dynabolt needs to be 45mm, plus your packers depth and/or flashing and then at least 50mm into the brickwork. You'll likely be looking for something close to a Ramset 12 x 125mm Hex Nut Dynabolt.

My recommendation for the screws would be self-drilling stainless steel. They'll save you a tonne of time by not having to pre-drill and countersink every screw hole in the Merbau decking.

If you haven't already read through it, @Adam_W's article on How to build a low-level deck is an excellent resource for what to consider when building a deck.

Please let me know if you have further questions.

Mitchell

[shez_89]

@MitchellMc Thanks a tonne for your advice - really helpful. I didnt come across the packers for brick installs but that was a good tip. Are you able to tell me why these are required? 

WIth the joists, would a 70x45 be better to go with in that case to allow another for more airflow?

Also what size angle brackets are advisable to use?

Cheers

Shez

[MitchellMc]

Hi @shez_89,

There needs to be a gap or flashing between your ledger board and your wall as you'll be generally attaching above the brick walls damp course line. If there is no gap, moisture can be transferred from your deck into the wall. If this then gets into the houses' timberwork, there can be issues.

More airflow is always better, though you'll need more supports for the 70 x 45 as it can't span as far unsupported. A bracket similar to the Wesfab 75 x 75 x 40 Galvinised Angle Bracket should be suitable.

Mitchell

[shauny]

@Backyardtradie Your picture framing, is it a 140mm board, with a board laying on its side with an additional 19mm space before your normal decking boards? I like that feature just inside of the wide board.

[Faheem]

Hi @Backyardtradie , your deck look so professionally done mate. Excellent job! 

i am going to build my own deck as well and need some guidance on the fixings. Whats the name and size of brackets you used to join joists with the concrete slab? And the screws or bolts you used? And the brackets you used to join joist with the beam at the end. 

And i can see you have one frame edging. What should  be gap between the two joists on the edges to support the frame? 

and lastly, i have clearance of 160-170mm. What combination of footings, bearers and joists you recon I should use? 

Thanks mate,

Faheem

[Faheem]

Nice work @Backyardtradie. just a quick one. What type of screws or bolts you used to connect the brackets with the concrete slab?

also, Do you have masonry drill? I have a regular 3amp makita drill. Will that work? 

[DIYImpressions]

@Backyardtradie  How did you manage to get this border done? 

 

[newhobby]

Looks awesome! I want to do the similar thing. Can i ask what materials are required?

[EricL]

Hello @newhobby

Thank you so much for joining the discussion. Let me tag @Backyardtradie to make them aware of your kind comments. The materials used for low-level decks are often framing timber and decking panels . But before you start I recommend reading this fantastic guide - How to build a low-level deck by @Adam_W. There you will be able to see the general idea of how to plan your deck. I suggest planning it on paper or computer so that you will have a better idea of what is involved in building a low-level deck.

Here is a link for ideas and inspiration: Inspiring low-level deck builds

If you have any other questions, please let us know.

Eric

[RussF]

Looks really good, inspirational

[Craig-G]

Hi People,

Very impressed with the updated look of the deck. Would like to consider something similar.

I have a large irregular shaped existing patio with tiles covering concrete. No drumming or loose tiles but very slippery when wet.

Can I just run treated pine slats, 450 centres, in the direction of the existing fall to fix the decking to?

If so, how do I fix these to the tiles/concrete?

Thanks

[EricL]

Hello @Craig-G

Welcome to the Bunnings Workshop community. It's fabulous to have you join us, and thank you for sharing your question about installing a low-level deck over tiles.

Unfortunately, if the timber slats are in direct contact with the tiles you'll get moisture contamination which will greatly shorten the life of your proposed deck. Not only that, but the slats being very thin will create a spongy deck and will provide no support to the decking panels. In regards to this type of installation, I recommend using treated framing timber in H3. The size of timber that you can use will depend on the clearance you have between your door and the floor area.

If you look at the second picture of the article you'll see that timber framing is below the door assembly. It has just enough space to install the decking panel. The timber framing is installed with angled brackets which are screwed down with Dynabolts onto the concrete base. In your case, you'll need to drill through the tiles and into the concrete base. It's not enough that the frame is only mounted to tiles.

Here is a link for ideas and inspiration: Inspiring low-level deck builds

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

Eric

[makhan006]

Hi

i like your project and i am planning to build similar . Could you please share the list of stuff i required for this?

Thanks

[EricL]

Hello @makhan006

It's great that you've been inspired by this decking project. Let me tag @Backyardtradie to make them aware of your kind words and question. 

Please keep us updated with your progress, we look forward to seeing the start of your decking project.

Eric

[Nikkigee89]

Hey,

this looks great! I have no experience making a deck, but I think I want to.

I built my first home, as a single mum, a few years ago and its on a downward hill so they built my slab up quite a bit. The side entrance is long and has dirt and rocks and you can visibly see the slap is stay higher than the boundary fence.

Can I make a deck that goes directly from the bottom of house/slab across to the boundary fence? It will start off level then the decking will be like 1 foot or so up the boundary fence. I know I'll need timber structure on the bottom, which will just fit at the beginning, but what would I attack the timber bottoms to? there's no conrete or flooring. I will get a pic when I can.
I just think my yard would be a nightmare to fill and put retaining walls around the boundary (don't even get me started on the backyard!)
Thanks so much,
Nicole.

[EricL]

Hello @Nikkigee89 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about building a deck.

It's great to hear that @Backyardtradie's decking project has inspired you to build your own. I suggest having a quick look at these guides - How to build a low-level deck by @Adam_W and How to build a deck by @MitchellMc. These guides will give you an idea of what you need to take into consideration when designing your deck frame. In order to give our members a better idea of your terrain, would it be possible for you to post a photo of where you plan on building the deck. We can then make recommendations on how to proceed.

I also recommend having a look at the Bunnings deck building video:

• How to plan out your deck
   
• How to set out a deck
   
• How to install stumps
   
• How to install bearers
   
• How to install joists
   
• How to lay decking
   
• How to add a step to your deck.

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

Eric

[NishanS]

Hi,

This looks like an amazing DIY project! I have a similar idea for my backyard, where I’m planning to build a low-profile deck with a height of 100 to 120 mm. However, my backyard currently has only grass, so I’m curious about how to build a low-profile deck on that surface.

While building a deck on concrete seems relatively straightforward, I understand that constructing one on grass may present some additional challenges. From my research, I’ve found that factors like termites, insects, poor ventilation, and drainage could complicate the process.

I’d greatly appreciate any suggestions or advice you can offer to help me get started with this project. Your input would be invaluable.

Regards

Nishan

[MitchellMc]

Hi @NishanS,

It’s great to see you considering the specific challenges of building on grass. Building a low-profile deck on grass is absolutely doable, but there are a few things to keep in mind to ensure the structure remains durable and well-ventilated.

If the soil will be in close proximity to the joists, particularly under 100mm, it's important to remove around 100mm of soil and replace it with drainage gravel. This step is important because it ensures proper drainage and airflow beneath the deck, preventing moisture buildup that could lead to issues like wood rot, termites, and mould growth. Gravel allows water to flow freely through the ground and avoids water pooling around the joists, which could compromise the integrity of your deck over time.

That said, building over soil is not a problem if you take the right approach. For stability, you can dig footer holes and then concrete in timber supports, ensuring the deck is elevated above the ground level. Alternatively, if you prefer to avoid digging too deep, you can compact the ground, lay pavers, and then use pedestal feet to support the deck. Pedestal feet are adjustable, allowing you to fine-tune the height of your deck, which is especially helpful for a low-profile build.

By addressing the drainage and ventilation concerns early on, you’ll have a solid and long-lasting deck.

Please let us know if you have any questions.

Mitchell