DIY Ideas – How to build a deck

Looking for DIY ideas to spruce up your backyard? Whether you’re updating your pool area, or creating a more organic indoor-outdoor flow, a DIY deck can dramatically lift the appearance and functionality of your space. So without further ado, here’s how to build a deck with your own two hands!

DIY Ideas - How To Build a Deck | ModularWalls
Start by sketching a detailed plan of your DIY deck

1. Plan your DIY deck

The first tool you need to pick up is a pencil; like any large DIY project, a deck requires some serious planning. Things to consider include:

  • What are the council approvals and building regulations/site setbacks for your local area?
  • Are there any underground services, such as cabling or pipes, to look out for when digging your foundations?
  • Will you need outdoor lighting or plumbing plans for your decking area?
  • Is there adequate drainage underneath your deck?
  • Is it protected from the weather or do you want to incorporate a shade structure?
  • How will your decking material age and what appearance are you looking for in 12 months’ time?
  • What tools and equipment are you going to need, on top of materials?
  • Are you working with soft ground, or is there rock or existing concrete/paving to consider?
Poolside lounge with HardieDeck – read full Case Study here

Material choice

Material choice is another big decision, and will ultimately affect the foundations you need. Whilst timber is affordable, it is also highly susceptible to rot or termites, or not suitable for bushfire zones. In this case, a composite deck (made from a mix of recycled wood fibres and plastic) may be more suitable. When choosing the thickness of the decking boards, remember that the thinner the planks, the more support they will need (i.e. shorter bearer and joist spans).

On the other hand, if your deck is being installed over rock or concrete, a modular deck kit may be a far easier and quicker alternative. These kits usually come with certain elements prefabricated, offer simpler foundations and can be installed over otherwise problematic ground conditions.

Finally, fibre cement decks, such as HardieDeck, offer a completely timber-free and very DIY-friendly alternative that has been highly favoured by many renovation gurus, including Three Birds Renovations.

Outdoor fireplace decking with bench seats

Deck design

When choosing your design, consider the natural terrain and the intended use of your deck. Some handy questions include:

  • Will the deck be flush with your home’s ground level, or will there be steps down to the deck?
  • Is the outdoor area level, or will you need a stepped deck edge?
  • Do you need to leave holes for trees or other design elements, such as pre-running cabling for lights or music systems?
  • Would you like to incorporate benches or other seating options within the deck?
  • Can you incorporate other unique DIY ideas, such as lighting or an outdoor fireplace, outdoor kitchen or outdoor shower?
Use string guides and spirit levels to mark out the site of your DIY deck

2. Measure your site

Once you’ve answered the above questions, grab your measuring tape and a notepad and head out to your site. Draw a detailed plan of your deck, including any graduation of the land; this will be important when laying the foundations, to ensure a level deck.

A typical deck will have four main structural elements:

  1. Vertical posts concreted into the ground, which bearers will be attached to; the ground conditions will dictate the foundation requirements.
  2. The bearers, which must be sized in accordance with your layout and required spans and deck loadings.
  3. The joists, which the decking boards will be fastened to. The spacing of these will also need to be determined in accordance with the decking board chosen, as different boards will have different span capabilities.

The ‘brainwork’ behind these elements can be fairly delicate; consult online span tables to calculate the correct bearer and joist spacings, according to your material choice. It may even be beneficial to consult with a deck builder, or to use an app like Quick Decks, to confirm these details.

Once these plans have been approved by the council, use the planning permissions and engineering specifications of your selected decking products to set out your deck. Ensure every detail is followed to the letter (or number!), as small errors will cause bigger implications later on. Pay particular attention to the maximum bearer spans; over-spanning your deck will severely affect the strength of it.

Using string guides, measure out your deck’s foundations according to your plans. Mark the ground where your string lines overlap; this will be where your stumps need to go.

3. Build strong foundations

For a great, sturdy finish, you need to invest in the unseen elements of your deck. A warped foundation will result in an unlevel deck, so when concreting the posts or stumps into the ground, remember to continue checking (and re-checking) measurements and levels regularly.

Once the concrete has set (best practice is to leave it overnight), it’s time to install the bearers and joists! The bearers support the joists and the joists are what your decking materials will sit on. Referring back to your plan and engineering specs, mark out where your joists should be installed and secure them to the bearers using appropriate screws or nails. Once again, keep checking those spirit levels.

Improve Your Yard With These 15 DIY Projects } ModularWalls
Secure each decking plank to your joists with a screw or nail

4. Lay the decking

It’s time for your deck to materialise before your eyes! Keep spacing between planks even and ensure you secure planks to each joist it crosses.

A typical spacing for a timber decking board would be around 3- 5mm. For easy DIY spacing, use offcuts with a nail through it. For a sleeker finish, use a Camo Hidden Deck Fastening tool, which ensures even spacing and hides the nails or screws from sight.

Also ensure your plumbing and lighting plan is kept in mind to avoid restricting access for cabling or piping work.

Once the decking is all secured, trim any excess lengths at the end with circular saw for a completely perfect edge.

Customised SlimWall with integrated lighting | ModularWalls
Seal your new deck with your choice of stain or oil

5. Seal your deck

The very last step is to seal your deck to protect it from premature aging against the elements. Consider the best stain or oil for your climate and architectural style; you need it to be both functional and aesthetically harmonious. It is also good practice to use a ‘deck wash’ first.

If you’re using timber, ensure the wood is first completely dried of all treatments it might have come with. As a test, pour a bit of water on the timber; if it beads, it’s still too wet, but if it soaks in, it’s ready for sealing.

And there you have it — your brand new DIY deck is ready to be styled and enjoyed! If you’re still hungry for the finer details, check out this awesome video collection, which goes through each and every step of their deck installation.

Written by Evelyn Kandris


Enclose your new outdoor entertaining area with an acoustically rated DIY modular fencing system that you can customise to your heart’s desire.

Explore the possibilities with ModularWalls today; use our online Quick Quote tool, call our friendly team on 1300 556 957  or fill out the enquiry form below. 

« Back to blog
Share this: