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How to Lay Decking

Posted on by Alex Leech
13
Nov

A simple, ground-level deck is a fantastic way to transform your outdoor space, adding extra functionality and impeccable style. If you’re keen to take on this project, start by consulting this handy guide. We’ll take you through how to lay decking and highlight the best products for a secure and professional finish. 

How to Lay Decking

Whether you’re carving out an area for outdoor relaxation, entertaining guests, or adding value to your home, proper installation is key to ensuring your decking lasts for years to come. In this guide, we’ll take you through the essential stages of building decking, including:

  • How to lay decking on soil
  • How to build a decking frame
  • How to lay timber decking 
  • How to lay composite decking

Preparation: How to Lay Decking on Soil

Before starting your deck project, we recommend sketching your design. This diagram helps you determine the dimensions, the number of deck boards you’ll need, and where your decking frame will sit. Once your design is ready, you can begin preparing the ground.

What You Will Need:

The Method

1. Mark the Site:

Measure the site according to your plan and mark the four corners with pegs. Then, run a builder’s line between the pegs to create a clear visual outline of the decking area.

2. Level the Ground: 

Next, ensure the ground is level. Clear away any interfering plants, rocks or weeds. Use an edger to make straight cuts into the lawn, then remove the turf with a spade. To confirm the ground is even, place a straight edge (like a deck board) on the ground, with a spirit level on top, and check that the whole site is level. Adjust any uneven areas as needed.

3. Prepare the Base: 

Finally, cover the area in a layer of weed control fabric and then add around 40mm to 50mm of gravel.

Alternative Method: Adding Concrete Pads

If you’d like, you can place your decking on concrete pads. This option makes the project slightly more complex but will help stabilise your deck and extend its lifespan.

1. Determine Pad Locations: 

After levelling the ground, decide precisely where the pads are required and dig holes roughly 150mm square and 150mm deep at intervals of 1.2m around the deck.

2. Fill the Holes:

Fill the holes with quick-drying, ready-to-use concrete up to just above ground level. Use a spirit level and straightedge to check that the pads are even with each other. If not, use a brick trowel to level off the highest points while the concrete is semi-dry.

3. Finalise the Area:

Once the concrete has hardened, cover the area with weed control fabric (making cut-outs for the concrete pads) and add a layer of gravel (40 to 50mm in depth).

4. Add Damp-Proof Course:

Cut and lay squares of damp-proof course between the concrete and the deck joists. This will act as a crucial moisture barrier.

Construction: How to Build a Decking Frame

Before starting your build, perform a dry run of the decking to avoid future issues that may compromise stability and appearance. Lay out the joist frame and position the deck boards on top, maintaining the necessary expansion gaps: 

  • Timber Deck Boards: Timber boards require a 5 to 8mm expansion gap along the length of the board and a 3mm gap along the ends.

  • Solid Composite Deck Boards: Composite boards need a 6mm expansion gap along the length of the board and a 3mm gap along the ends.

If you find that the timber deck boards on the end row overhang the joist frame, you can consider adjusting the expansion gaps within the recommended 5 to 8mm range. However, remember that solid composite boards have a standard 6mm expansion gap that cannot be altered. Alternatively, you could adjust the outer frame so that your final decking row finishes flush with the edge of the joist frame.

What You Will Need:

The Method

For clarity, we’ll split the frame construction into two parts: the outer joists and the inner joists.

Outer Decking Joists Method:

This part of the process involves creating the perimeter of your frame.

1. Cut or Join to Create Correct Size: 

Measure your deck frame and cut it to size. If your decking is planned to exceed the length of the joists, you’ll need to join two joists together to achieve the correct length for the frame.

2. Position the Frame:

Once the outer frame is the correct size, move it into position. Ensure it is level before securing it – using risers, paving slabs or timber offcuts at 500mm intervals can help. Verify that the corners are square using a set square.

3. Join the Frame:

Line up the adjoining outer joists, mark and drill a pilot hole, then fix two external-grade timber screws into each corner. If the external corners of the frame are hard to access, drill skewed pilot holes at a 45-degree angle into the wood and, again, drill in external-grade screws.

Internal Decking Joist Method: 

When the outer frame is constructed and positioned correctly, it is time to secure the inner joists.

1. Mark Spacing of Inner Joists: 

Measure and pencil mark the even spacing of your inner joists. The spacing of your joists can vary depending on your chosen decking design.

2. Attach Joist Hangers: 

Secure the joist in your workbench and attach a joist hanger to each end. This hanger will strengthen the deck’s load-bearing ability and improve structural integrity.

3. Position the Joists: 

Place the joist into position so the centre lines up with your pencil marking. Ensure the joist end is flush with the frame.

4. Drill and Secure: 

Drill pilot holes into the external face of the frame. Then, drill countersink holes and secure the joists using timber screws. Repeat this process for the rest of the internal joists, constantly checking that the joists’ ends are flush with the frame. 

 

How to Lay Timber Decking

Timber decking is a popular choice for many homeowners, favoured for its durability, low maintenance and natural appearance. Choose your favourite timber decking boards and measure and cut with a mitre saw, hand saw or jigsaw if necessary. You could also apply a protective treatment to the cut or recessed timber. 

What You Will Need:

The Method

1. Position the First Board: 

Begin at one corner of the sub-frame. Place the first timber decking board across the inner joists, ensuring it runs opposite the joists and sits flush with the frame.

2. Secure the First Board: 

Secure the board to every joist it crosses along the sub-frame, using two screws where each board meets a joist. To prevent the wood from splitting, drill pilot holes for the screws and countersink them if necessary for a smooth finish. If laying grooved deck boards, position the screws at the bottom of a groove.

3. Lay the Next Rows:

Continue laying the subsequent rows, ensuring you leave the appropriate expansion gaps between each board. You can use spacers to maintain even gaps if necessary.

4. Finish the Edges: 

Use sandpaper or a sander to smooth any roughly cut ends. Afterwards, you can apply a timber preserver to protect the wood from rot and decay. 

 

How to Lay Composite Decking

Fitting composite decking doesn’t require specialist tools – you can use the same ones as timber decking. However, composite decking fixings involve a slightly different method. The grooved edges of solid composite boards are designed for a hidden fastening system, creating a clean, seamless finish. Here’s how to achieve this sleek installation.

What You Will Need:

  • Composite Decking Boards 
  • Starter Clips (usually packaged with screws and a drill bit)
  • Hidden Fasteners (usually packaged with screws and a drill bit)
  • Drill

The Method

1. Fit the Start Clips: 

Begin at one corner of your decking area. Attach the start clips along one edge of the outer joist, centring each clip on each outer and inner joist. Secure the clips with the screws and drill bit provided.

2. Position the First Board: 

Push the grooved long edge of the first composite deck board into the start clips, ensuring the board is straight and securely positioned.

3. Slide the Hidden Fastener: 

With the first board in position, slide a hidden fastener into place so it sits within the groove of the deck board. These fasteners ensure a consistent 6mm expansion gap between the boards. Align the screw hole in the fastener with the centre of the joist, and screw it in about 75% – but don’t fully tighten just yet. Repeat this process along the length of the board, semi-fixing at every joist.

4. Position the Second Board: 

Slide the second board into place, ensuring the hidden fasteners sit neatly into the groove. Avoid forcing the board; it should fit smoothly. Then, repeat the above process, adding the next set of hidden fasteners on the other side of the second board. Again, do not fully tighten the screws at this point.

5. Tighten the First Row: 

Once the second board is semi-secured, you can go back and fully tighten the screws on the hidden fasteners on the first row. Repeat this process for each successive decking board you lay down. Remember you must lay down the next board before fully tightening the screws on the previous board.

Find Essential Decking Supplies at Building Shop.

Before commencing work on your new garden structure, head to Building Shop for essential decking materials and fixings. We offer competitive prices and timely delivery of your order, so there are no delays in your upcoming project.

Please don’t hesitate to contact us if you require any assistance with your supplies. Simply call 01372 230 830 or email sales@buildingshop.co.uk to speak with our friendly team of experts who will be happy to help.

Alex Leech