How to Build a Deck

Step-by-step guide to building your own deck

 

It serves a fabulous centrepiece, brings the family together and increases the value of your home.

Building a deck is a fantastic way to enhance your outdoor living space and add value to your home, and Merbau timber is an excellent choice for decking due to its durability and rich colour. If you need a deck in your life, but want to save some cash, why not go the D.I.Y. route? We’ll show you how to get it right the first time. This step-by-step guide will help you build a beautiful and functional deck, complete with steps, picture framed edges, planter boxes! 

Safety tip: Always wear the appropriate safety equipment (safety glass, ear muffs, gloves and mask, for example) and always follow the instructions for the product or equipment. 

 

 

 

TOOLS

  • Measuring tape 
  • Spirit level 
  • String line 
  • Hurdles 
  • Shovel 
  • Post hole digger 
  • Saw 
  • Drill and bits 
  • Hammer 
  • Nail gun 
  • Circular saw 
  • Angle grinder 
  • Paintbrush 

 

MATERIALS

  • Merbau timber (for decking, framing, and screen) 
  • Spray paint 
  • Timber stumps 
  • Bearers and joists 
  • Decking screws and nails 
  • Concrete 
  • Bitumen paint 
  • Decking oil 
  • Weed mat 
  • Planter box liners 
  • Gravel  
  • Soil 

 

STEPS

How to set out your deck 

1. Mark out your deck area 
First things first, sketch out your deck on some paper and then take a look at your local council guidelines and make sure your plans are above board. Then grab your tools and materials and head outside. Take some marking paint and roughly mark out your deck, as this will help you visualise the size of your deck and plan where to place your hurdles. 

At this stage you can make any changes to the orientation, the sizing and or other design elements you’d like. 
Marking the deck area
2. Place your hurdles 
The key to a successful deck build is taking steps to create guides to ensure everything is plumb and straight at each step. The first way to do this is by installing temporary hurdles at each corner of your future deck, about half a metre away from the actual perimeter. Hammer star pickets into the ground and attach timber to the pickets. Use a level to make sure it’s straight before inserting a screw at the top of each hurdle.  
Installing temporary hurdles at each deck corner
3. Run the string line 
Next, use a string line to define the shape and dimensions of your deck. Take your string line and stretch it along the outer edges of the screws on each hurdle to create the shape of your deck.  
Using a string line to measure the deck's dimensions
4. Check string line is squared 
Once the strings are in place, use the 3/4/5 rule to ensure the deck is square. Measure 3 metres in one direction, 4 metres in another direction, and the diagonal between these points should be 5 metres. 
Strings on the deck ensure it is square


How to install stumps 

5. Measure and mark where the stumps go  
To determine how high you can have your deck, check with your community guideline local span table and sure you’re compliant. Then decide on the spacing for your joists and beams. Common spacing for joists is 400mm on centre, but this can vary depending on your design and load requirements. Stump spacing is typically determined by the size and spacing of your bearers and joists. For example, timber stumps might be spaced 1.2-1.8 metres apart along the bearers. Once you’ve figured out the spacing of your stumps, mark out where the stumps will go with spray paint and install string lines to guide you.  

For reference, joists are the horizontal planks that provide support to the decking boards, bearers are larger horizontal planks that support the joists, and stumps are the vertical posts that transfer the load from the beams into the ground and keep the deck elevated and stable! 
Marking the stumps placement with spray paint
6. Dig the holes 
Once you’ve marked out where your stumps will go, use a shovel or an auger to dig the holes for your stumps. Make sure that you dig your hole so that the stumps will be centred when lowered in. Dig until you’ve reached at least 100mm of stiff clay. A general guide is to dig 300x300mm by 600mm deep. Roughly drop the post in to make sure it fits and that you’ve got the height correct. 
A person is digging the holes using a hole digger
7. Paint the stumps 
When cutting your stumps, make sure you leave them a bit longer than you need so that you can trim them to the correct height once they’ve been laid down. Before placing the stumps in the holes, coat the part of the stump that will be in contact with the ground with bitumen paint. This protects the timber from moisture and rot. Allow the bitumen paint to dry completely. 
Painting the stumps with permanent waterproof paint
8. Mix concrete 
When your stumps are dry, mix quick set concrete in a wheelbarrow according to the manufacturer’s instructions. You’ll need enough to fill each hole approximately half way, with at least 150mm of concrete on the bottom for your stump to stick into.  

9. Place the stumps in and backfill with soil 
Fill each hole one by one about halfway with concrete and place the stump in, making sure it’s plumb and lined up with the string lines you installed earlier, and backfill with soil. Allow this to cure for 24 hours. Try to get the stumps all the same height, but don’t worry too much because you’ll cut them all to the correct height when they’ve set.  
Using a spirit level to ensure all the stumps are the same height
10. Mark and cut the stump 
Now it’s time to cut your stumps to height. Follow the equation below to get the height needed. 

Height of stumps = Overall height of deck - overall height of joists, bearers & decking 

Mark this on each stump and cut to the specified height. SpecRite recommends a minimum height clearance of 400mm. When this is not possible, increase gapping, ensure cross flow ventilation, and provide drainage to minimize excess moisture buildup. 
A person is cutting the stumps to the required height


How to install screening posts 

11. Install stirrups 
If you’ve chosen to include screening in your deck design, now is the time to add in your stirrups to support your screening posts. Dig holes at specified intervals along the deck perimeter or where your screening will be. Place your stirrups into the holes and with their anchor bolts set in concrete in line with your stringline. Backfill with soil for stability and allow to cure for 24 hours. 
Installing stirrups to support the screening posts
12. Add posts for screening 
Pre-drill holes into each screening post before bolting them into the stirrups and then cut to the height according to your screening height. To keep your posts straight, install some temporary bracing posts by hammering pickets into the ground first. Then lay a plank of wood alongside the screening post and screw this into the picket to keep the screening post straight. 
Adding the screening post and screwing it into the picket


How to install bearers 

13. Measure bearers 
Now it’s time to attach your bearers and joists. The bearers have to carry the weight of the entire deck and whatever is put on top of it, so they need to be strong. A 140x45 treated pine bearer for decking will usually do the trick, and they’ll need to run the span of the deck (and parallel to the length of the deck).  
Attaching bearers and joists to support the weight of the entire deck
14. Cut bearers 
Once you’ve measured up, cut your bearers to size. 

15. Installing bearers 
For extra support, you’re going to nail your bearers together using a nail gun. Next, nail your bearers into your stumps with a nail gun. Then tie down your bearers with hoop iron and secure them with a drill and screws. 

To provide extra support to each bearer, mark out the locations under each bearer where it meets the post. Secure each bracket with stainless steel screws , ensuring all connections are level, properly aligned, and follow local building codes.  
Holding a piece of timber and a nail gun


How to add a step to your deck 

16. Measure and mark where the stump will go for the step 
Now, if you’re adding one, it’s time to build the step that leads up to your deck. Typically, for steps on a deck, the stumps or support posts will be placed at the ends of each step and at intermediate points along longer steps for additional support. Mark out the hole placements for the stumps. Then, a general guide for step height is to divide the height of your deck to ensure you get a maximum height of 190mm and a minimum height of 110mm.   

17. Dig the holes and insert stumps 
Repeat the steps from when you installed the first stumps by digging out each hole using a shovel or auger.  Paint each stump with bitumen like earlier and allow to dry. Then mix up the concrete in your wheelbarrow according to the manufacturer's instructions with a shovel and fill each hole halfway.  Place the painted stump in, ensuring again that there’s at least 150mm of concrete at the bottom to secure the stump and ensure it’s level and plumb. Backfill each hole and allow the concrete to set for 24 hours before cutting your stumps to height. 
Digging holes using a hole digger
18. Create box frame for step 
Using timber, create a box frame for your step.  Attach it to the stumps with a nail gun. 

19. Attach rubber to bearers 
Then to protect the timber from weather conditions, you’re going to use a staple gun to apply rubber stripping along the tops of the bearers. This protects the timber from moisture and rot.  
Attaching rubber to bearers using a staple gun


How to install joists 

20. Measure and mark joists 
Moving on to the joists, the next layer of support you’re going to install. Take the width of your deck and divide it into even sections no more than 450mm apart. Mark this out along the bearers on the perimeter of your deck. Then remember how we talked about creating guides to make things easier and more level? This is where the chalk line comes in. Use a chalk line to plot out where each joist will go along all your bearers so that you’ve got the perfect grid to know where to place each joist.  
Installing joists along the bearers to create a precise grid for placement
21. Nail joists on bearers 
All that’s left to do is to place a joist over each chalk line and nail into place using a nail gun and galvanised nails. Screw in metal support brackets along both sides of the joist on top of each bearer and then ahead and staple rubber strips along each one like you did with the bearers earlier. 
Using a nail gun to attach nails to metal support brackets  


How to add garden beds into your deck 

23. Add in planter box 
Now if you’ve added any feature areas into your decking design, it’s time to build them out. For our example, we’ve chosen planter boxes for plants. Raised garden beds add a pop of greenery and are really easy to install. You can simply drop in a timber or metal frame that you can fill in with soil and plants later.  



How to lay down the perimeter line of your deck 

24. Mark out picture frame for perimeter line 
If you are planning to install a picture frame (a border of decking boards around the perimeter), measure and mark the location of the inner edge of the picture frame. This is typically set back from the outer perimeter by the width of one or two boards, depending on your design. For a clean and professional look, mitre cut the ends of the decking boards at 45-degree angles where they meet at the corners. Ensure the cuts are precise for a tight fit.  
A person is screwing nails into a frame  
25. Screw picture framing into place 
Pre-drill holes near the ends of each framing board to prevent splitting, then screw the picture framing into place. For extra support, place noggins horizontally between the joists or beams along the inner edge where the picture frame will be attached. Secure the noggins by screwing or nailing them into place, using galvanised screws to prevent corrosion. 

 

How to lay decking 

26. Mark out intermediate boards and screw into place 
Just like the step before, you’re going to mark out where each board goes using chalk line. It is recommended to leave a gap between planks that is equal to 5% of the board's width. Then, screw in every 5th board. This is going to maintain consistent spacing and alignment of the deck boards. It acts like a reference point, ensuring that all boards are laid straight and evenly spaced. 
The deck boards are laid straight and evenly spaced  
27. Cut remaining boards and lay out on deck 
Cut the remaining boards to size, then place all your boards down according to the chalk grid and make sure they all fit.  Create chalk lines on top of your boards for where the screws will go. Doing this is going to make your job a whole lot easier and give you a clean finish.  
Laying down deck boards ensuring proper fit  
28. Drill boards and joists 
If the boards aren’t long enough and you need to join boards, make sure you stagger the joins, but ensure they sit on top of a joist. Not only does this look more aesthetically pleasing, but it distributes the load of the deck more evenly.  To prevent splitting, pre-drill before going ahead and screwing the boards in, making sure they are countersunk for a smooth finish. Use spacers to create even gaps between each board.  
Using drill to screw the boards into the deck

 
How to install plinth boards 

29. Install plinth boards 
For a clean, professional finish, install plinth boards around the perimeter of your deck to hide the stumps. Cut them to size, allowing for a 20mm gap between each for air flow. Position the boards along the base of the deck, ensuring they are level, evenly spaced and aligned. Secure them in place using screws or nails.  
Installing plinth boards around the perimeter of the deck  


How to stain a deck 

30. Tannin wash 
Merbau timber is known to leach tannins when it gets wet. Before using the deck, wash it down with a tannin wash, brush to apply evenly and then hose off.  Let it dry completely. 
A brush is evenly applying stain to the deck  
31. Oiling 
Once the timber is dry, apply a decking oil to protect the wood and enhance its natural colour. Using a brush, roller, or sprayer, apply the oil evenly along the grain of the wood, starting at one end of the deck and working your way across. Follow the manufacturer's instructions for application and drying times, and allow it to dry completely before using your deck. Remember, Merbau arrives pre-oiled, so only one coat is necessary. Applying a decking oil regularly will nourish the wood, enhance its natural colour, and provide protection against the elements. Oil your screening posts at the same time. 

 

How to install screening 

32. Add screening 
Secure the screening timber to the screening posts, ensuring each one is level and use spacers for uniform gaps. Use screws or nails to fasten the screening securely, and trim any excess material for a clean finish, working from top to bottom. Remove the supports and oil the screening timber as you did the deck.  
Securing screening timber to posts
 

Finishing touches for the deck 

33. Add decorative features 
Lastly, it’s time to add in your final decorative features. We’ve gone for native plants, outdoor furniture for awesome entertaining, and cladding for privacy. 

Building a deck with Merbau timber can be a rewarding D.I.Y. project that transforms your outdoor entertainment area . With careful planning and attention to detail, you'll create a beautiful and durable deck that you can enjoy for years to come. 
Adding plants to the deck as final decorative features