Installing your own deck is a manageable weekend project if you plan properly and have the right materials on hand. This guide walks you through the full process, from measuring your space to fixing the final board, whether you're working with timber or composite decking.
What You'll Need Before You Start
Before you begin, make sure you have the right decking boards and accessories ready:
● Your choice of Timber Treated Decking Boards or Composite Decking Boards
● Decking Joists to build the sub-frame
● Screws & Clips for fixing boards securely
● Decking Trims for a finished edge
● Handrails if your deck is raised or you want added safety
● A spirit level, tape measure, drill/driver, saw, string line and postcrete (for posts, if raised)
If you're still deciding between materials, our guide on Composite vs Timber Decking can help you choose before you buy.
Step 1: Plan and Measure Your Decking Area
Mark out the area with string lines and pegs, and measure it carefully to work out how many boards, joists and fixings you'll need. Always add 5–10% extra to your board order to account for cuts and wastage. Check whether your project needs planning permission — most ground-level garden decks in the UK don't, but raised decks near boundaries sometimes do.
Step 2: Prepare the Ground
Clear the area of grass, weeds and debris. For a ground-level deck, lay a weed-suppressant membrane and a bed of gravel or paving slabs to support the frame and prevent damp rising into the joists. Make sure the base is level before you continue.
Step 3: Install the Sub-Frame (Joists)
Lay your joists at 400mm–450mm centres for standard boards (check the spacing recommendation for your specific board thickness). Use a spirit level throughout to keep the frame flat, and fix joists to support posts or a ledger board if the deck is attached to your house. A solid, level sub-frame is the single biggest factor in how long your deck lasts.
Step 4: Lay and Fix the Decking Boards
Starting from one edge, lay your first board flush against the frame and fix it using screws or hidden clips, depending on your board type. Leave a small consistent gap (usually 3–5mm) between boards to allow for drainage and natural expansion — this matters more for timber, but composite boards still need some breathing room in changing temperatures. Continue board by board, checking alignment regularly with a string line.
Step 5: Add Trims, Edging and Fascia
Once the main boards are down, finish the exposed edges with decking trims or fascia boards. This covers the joist ends, gives a clean professional finish, and protects the frame from direct weather exposure.
Step 6: Install Handrails (If Needed)
If your deck sits above a certain height (typically anything over roughly 600mm in the UK), a handrail is a safety requirement, not just a style choice. Our handrails range includes posts, spindles and railings designed to match both timber and composite builds.
Timber vs Composite Installation — Any Differences?
The installation method is largely the same for both materials — joists, spacing, fixing — but there are a couple of differences worth knowing:
● Timber boards often need pre-drilling to avoid splitting, especially near the ends.
● Composite boards usually use hidden clip systems for a screw-free surface finish, which composite manufacturers specifically design their board profiles around.
If you haven't chosen your material yet, see our Composite vs Timber Decking comparison for a full breakdown.
Common Mistakes to Avoid
● Skipping the membrane and gravel base, which leads to damp and rot underneath the deck
● Spacing joists too far apart, causing boards to flex or sag over time
● Forgetting expansion gaps between boards
● Not checking level regularly during installation, resulting in an uneven surface
Frequently Asked Questions
Do I need planning permission to install decking?
Most single-storey garden decks under 30cm in height and covering less than 50% of your garden don't need planning permission, but it's worth checking with your local council if your deck is raised or near a boundary.
How long does it take to install a deck?
A standard garden deck (around 3m x 3m) typically takes one to two days for a confident DIYer, longer if ground preparation or raised framing is involved.
What spacing should I leave between decking boards?
A 3–5mm gap is standard for both timber and composite boards, allowing for drainage and material movement.
Can I lay decking directly onto grass?
No — always clear the area and lay a membrane with a gravel or slab base to prevent damp and weed growth underneath the deck.
Ready to get started? Browse our full range of Timber Treated Decking Boards, Composite Decking Boards, and everything else you need in All Decking Boards.