How To Plan & Install Garden Decking

Adding decking is one of the best ways to transform your garden into a practical and attractive outdoor living space. Whether you’re creating a seating area, entertaining space or pathway, careful planning and preparation are key to a long-lasting deck. Follow our simple guide below to learn how to install decking correctly, and don’t forget to explore our recommended products at the end of this article to help complete your project.

Tools & Materials You’ll Need

Step 1: Plan Your Deck

Good planning is essential before you begin. Start by sketching a rough design of your deck or marking out the area using timber battens to help visualise the finished size.

Draw a simple scale plan showing:

  • House walls
  • Doors
  • Air bricks
  • Drain covers
  • Trees and obstacles
  • Wastewater soakaways

If your deck is attached to your home, make sure the finished deck level sits at least 150mm below the damp proof course (DPC) to comply with building regulations.

Remember to leave access to inspection chambers and avoid covering air bricks.

Step 2: Measure the Area

Calculate the total size of your deck in square metres to work out how much decking you’ll need.

You’ll also need to calculate the number of:

  • Deck boards
  • Joists
  • Posts
  • Fixings

If you’re unsure, bring your deck plan into your local Buildland branch and our team will be happy to help calculate your materials.

Step 3: Prepare the Ground

Mark out the deck using pegs and string before removing all grass, weeds and vegetation from the area.

Lay weed control fabric over the ground to help prevent future weed growth beneath the deck.

The decking frame should always sit on a solid base rather than directly on the soil.

For most garden decks:

  • Lay concrete paving slabs in a grid approximately 1.4 metres apart
  • Check each slab is level
  • Ensure the deck falls 10mm per metre away from the house to allow rainwater to drain

If the ground is particularly soft or has poor drainage, create stronger concrete foundations by digging holes approximately 300mm square and 300mm deep, then fill with concrete and allow it to cure.

Finally, place pieces of DPC membrane between the concrete supports and the timber frame to protect the timber from moisture.

Step 4: Build the Frame

Construct the outer frame using 150mm x 50mm treated timber joists.

Fix the corners together using:

  • Exterior wood glue
  • 100mm rust-resistant screws

If attaching the deck to your property, fix the wall plate to the house using stainless steel washers to create a minimum 10mm ventilation gap between the timber and wall.

Use a spirit level to ensure the frame remains level while maintaining the slight fall away from the house.

Next, install the internal joists at 400mm centres, running at right angles to the direction of the decking boards.

Step 5: Lay the Deck Boards

Before laying the boards, fit short timber noggins between the joists to strengthen the frame.

Begin laying decking boards from the house outward.

For best results:

  • Leave approximately 5mm gaps between each board for drainage and expansion.
  • Use stainless steel or galvanised decking screws.
  • Pre-drill all fixing holes to reduce the risk of splitting the timber.
  • Fix each board at every joist.
  • If joining boards, always join them over a joist and stagger the joints for a more attractive finish.

Continue until all boards have been securely fixed.

Disclaimer: This guide is intended for general information only. Buildland accepts no responsibility for any injury, loss or damage resulting from the use of this guide. Always follow manufacturer instructions, relevant building regulations and current health and safety guidance. All work is carried out at your own risk.

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