Composite decking installation doesn’t necessarily require a professional if you follow the right steps and consider a few essential guidelines. It is also an increasingly popular choice for garden areas, sturdy patios, and outdoor pathways due to its weather resistance, visually appealing appearance, and low maintenance.

Step-by-Step Composite Decking Installation

For a successful composite decking installation, proper planning, a solid base, and quality materials are key.

Planning and Measuring

Begin by measuring the exact dimensions of your decking area. It’s advisable to sketch a layout plan, including the decking pattern, fixing points, and structural support locations. Be sure to account for thermal expansion during planning, as composite materials—made from a blend of recycled plastics and other durable components—can expand and contract with temperature changes.

Preparing the Base

The foundation should be solid, level, and stable. Suitable bases include concrete slabs, pressure-treated timber beams, or even metal structures. Support the base structure every 30–40 cm to prevent sagging or settling over time.

Building the Joist Frame

Typically, WPC or pressure-treated wood joists are used beneath composite decking – but our recycled plastic decking subframe joists are also an excellent choice. Fix the joists securely to the base, ensuring they are perfectly level. The gap between joists should not exceed 35 cm to avoid flexing or sagging of the decking boards.

Laying the Composite Boards

Use a clip system to attach the boards to the joists without visible screws. Leave a 5–7 mm gap between boards to allow for thermal expansion. Use end caps or edge profiles for a clean, finished look and to increase durability.

Edging, Ventilation, and Finishing Touches

Use trim boards or aluminium edging profiles to close off the decking edges. Ensure the area beneath the deck is well-ventilated to avoid moisture build-up and prevent mould growth.

Mistakes in Composite Decking Installation

Even DIY enthusiasts often make avoidable mistakes during composite decking installation that may compromise the long-term quality of the decking. These typically include:

Inadequate Joist Spacing

One of the most frequent errors is exceeding the recommended 35 cm spacing between joists. This can lead to the decking sagging or warping, both structurally and visually.

Ignoring Expansion Gaps

Composite materials expand with heat and contract in the cold. Always leave adequate spacing between boards and at wall edges. Failing to do so may cause boards to warp, crack, or buckle.

Incorrect Fixings

Using fixings not recommended by the manufacturer can lead to boards shifting or cracking during use.

Poor Drainage

The area under your deck must be well-drained. Standing water can cause structural damage and encourage mould or fungus growth over time.

Composie Decking Maintenance Tips

One of the key benefits of composite decking is its minimal maintenance requirements. That said, a few simple routines can help preserve its appearance and durability over time.

Regular cleaning during the spring and autumn is highly recommended. A pressure washer or garden hose will remove general dirt and debris, while tougher stains can be tackled with soapy water and a soft-bristled brush – strong enough to clean, yet gentle enough not to damage the surface.
 

In shaded or damp corners of your deck, moss and algae can sometimes take hold. When this happens, opt for an anti-algae treatment designed specifically for composite materials. Avoid using harsh chemical cleaners, as they may damage the finish of the boards.

During the winter months, snow should be cleared using a plastic shovel to prevent surface scratches. For ice, it's best to allow it to melt naturally rather than using metal tools or aggressive ice-melting agents that could harm the decking.

To guard against physical damage, it's a good idea to place protective pads under the legs of outdoor furniture. You should also avoid placing hot grills or fire pits directly onto the decking, as the extreme heat may cause permanent surface damage.

Repairing Damaged Composite Decking

Even with a well-executed composite decking installation, minor damage such as scratches, cracks, or discolouration can occasionally occur. Fortunately, these problems are usually easy to remedy.

Light surface scratches can often be removed with a gentle sanding using fine-grit sandpaper. As the decking weathers naturally, the sanded area tends to blend in with the rest of the surface, making the repair barely noticeable.

If a board becomes cracked or broken, it can typically be replaced without too much trouble. Clip systems make this especially simple, allowing individual composite decking boards to be lifted out and swapped. For screw-fixed boards, just remove the screws and install a new panel in its place.

Stains or areas of discolouration should be cleaned using warm soapy water or a specialised composite deck cleaner. Steer clear of petrol, solvents, or abrasive scouring tools, as these can leave permanent marks or degrade the material.

Final Thoughts

A properly executed composite decking installation is not only attractive but also highly durable. With careful planning, correct installation, regular maintenance, and quick repairs when needed, your decking will stay in excellent condition for years to come.