How to Lay Composite Decking

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Installing composite decking can be a straightforward process, depending on the location and your preference for sun or shade. Being prepared is key for a successful installation. For detailed guidance on preparation, fitting, and maintenance, always refer to the decking manufacturer's instructions. Following their guidance ensures correct installation and also safeguards any warranties. In rare cases, you may need planning permission, so it's advisable to check with your local council for further advice.

Before starting your project, gather essential tools like a tape measure, cordless screwdriver, mitre saw, jigsaw, drill, rubber mallet, and a deck fastener-compatible gun if needed. When constructing the composite decking subframe, use structurally treated timber for durability in all weather conditions. Ensure the ground is level and free from debris before securing the timber to form the foundation of your deck. 

Decking tools you’ll need

When tackling a project on fitting composite decking, having the right tools is essential to ensure an efficient installation process. Proper preparation facilitates the installation and guarantees a durable and aesthetically pleasing finish. Composite decking steps involve precision and care, from initial measurements to the final fitting. Here is a list of essential tools required for composite decking installation:

• Tape measure

• Cordless screwdriver 

• Mitre saw

• Jigsaw

• Drill

• Rubber mallet

• Deck fastener-compatible gun (optional)

What is the best foundation for composite decking?

A sturdy and level foundation is essential for laying composite decking and ensuring its longevity and stability. The best materials for this purpose include concrete, pressure-treated timber, plastic lumber, and aluminium. Each of these materials offers unique benefits, such as durability, resistance to moisture, and ease of installation.

Concrete

Concrete offers a strong, stable base perfect for composite decking, being highly durable and able to withstand heavy loads and harsh weather. It also offers a long lifespan with minimal maintenance.

Pressure-treated timber

Pressure-treated timber is favoured for its affordability and easy installation. Treated with chemicals to resist rot, insects, and decay, it's a reliable choice for decking foundations. Ensure the timber is rated for ground contact for the best results.

Plastic lumber

Plastic lumber is made from recycled plastics and offers excellent resistance to moisture and decay. It requires little maintenance, making it a convenient option for composite decking foundations. Its durability ensures that it will not warp, split, or rot over time.

Aluminium

Aluminium, a durable and lightweight material, offers a stable base for composite decking. Resistant to rust and corrosion, it's perfect for outdoor settings. Easy to handle and install, saving time and effort during setup.

Steel frames

Steel frames offer unrivalled strength and durability, suitable for large or elevated decks. They are resistant to warping and weather damage, ensuring a long-lasting foundation. Steel frames are often preferred for commercial applications or areas requiring additional structural support.

How do you build a deck frame for composite decking?

Timber will provide the basic framework of your composite decking subframe, arranged in rows. When building a composite decking framework, use structurally treated timber for durability in all weathers.
Try to avoid building timber frames and joists in wet weather. Even with treating and damp-proofing this might lead to some distortion to the wood that can throw off your measurements.

There are different methods in approaching how to build a decking frame. This can vary depending on space, how level the ground is and so on. Guidance for planning your subframe, and how to lay composite joists, is as follows:

This guidance should give you an idea on how to prepare, and the steps to consider, when building your new decking. However, there are variations in styles and designs in composite decking, so as previously mentioned, follow manufacturer’s instructions and guidelines for details on laying decking.

How to Lay Composite Decking: FAQs

What do you put under composite decking?

You should put a solid foundation, typically consisting of a pressure-treated timber or aluminium subframe, under composite decking. This ensures stability and longevity. The foundation is the most critical aspect of any decking project. For composite decking, using pressure-treated timber or aluminium subframes provides a robust and durable base. This helps to prevent warping and ensures that your decking remains level over time. Additionally, a weed control fabric can be laid under the frame to prevent weed growth, ensuring a clean and low-maintenance space beneath your decking.

What do you fasten composite decking with?

Composite decking is typically fastened with either screws or hidden fasteners, depending on the board design and the desired aesthetic. The decision between screws and hidden fasteners hinges on the desired look and the type of composite decking boards. Screws offer strong holding power, ideal for high-traffic areas. Hidden fasteners provide a cleaner appearance by concealing the system beneath the decking. Both methods secure the decking to the subframe, ensuring a stable, durable structure. Always refer to the manufacturer's instructions for best guidance.

Do you need a gap in composite decking?

Yes, a gap is necessary between composite decking boards to allow for expansion and contraction due to temperature changes. Proper spacing between composite decking boards is crucial to accommodate the natural expansion and contraction that occurs with temperature fluctuations. Typically, a gap of 5-8mm is recommended. This spacing prevents the boards from warping or cracking over time and allows for proper drainage, which helps maintain the integrity of the decking and prolongs its lifespan.

Can you put composite decking directly on concrete?

While composite decking can be installed on concrete, it is necessary to use a sleeper system to ensure proper ventilation and drainage. A sleeper system involves placing a layer of pressure-treated wood or metal framing on top of the concrete. This creates a gap that facilitates ventilation and drainage, preventing moisture buildup that could damage both the decking and the concrete over time. This method provides a solid base while ensuring the longevity and performance of your composite decking.

If you want to know more about the benefits of composite decking and aftercare, we have more gardening articles for you to read up on!

Disclaimer: The information contained on this page is intended as an overall introduction and is not intended as specific advice from a qualified professional. Travis Perkins aims to avoid, but accepts no liability, in the case that any information stated is out of date.

Always refer to the manufacturer's guidance and installation instructions.