Composite decking buying guide

Composite decking buying guide

Jenny, construction and gardening writer, Oxford

Guide written by:

Jenny, construction and gardening writer, Oxford

Composite decking is the perfect low maintenance alternative to softwood and exotic wood decking. Whether you have a large or small space to work with, composite decking boards and tiles come in a range of different types (e.g. hollow, semi-solid or solid) and colours to match to your exterior walls and garden décor.

Important features

  • Features
  • Materials and quality
  • Format and size
  • Accessories and maintenance
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How to choose composite decking: the basics

Couleur et aspect des dalles ou lames pour terrasse en bois

The benefit of composite decking is that it requires little maintenance. Want to pick the perfect decking boards? Think about the following criteria:

  • the size and format of the boards which should be chosen to match the dimensions and purpose of your decking;

  • the plastic-to-wood percentage (generally 50 to 70%);

  • density (750 to 1400 kg / m3);

  • finish type and colour to suit your preferences;

  • type of profile (hollow, solid or semi-solid);

  • budget.

What is composite decking?

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Composite decking: a definition

Composite is a material that combines wood products with plastic and typically contains the following:

  • natural fibres: flax shive, wood flour, hemp, bamboo, sawdust, etc.;

  • polymers: PVC, polyethylene (PE), polypropylene (PP) (which determine mechanical properties);

  • pigments: dictates the colour of the material;

  • additives: anti-fungal treatments, hardeners, etc. ;

  • UV stabilisers for durability.

Composite finishes

Composite is made to look like exotic wood in terms of wood grain, fibres, colours, and so on. Available in decking boards and decking tiles, composite is always through-coloured but it can feature a solid or hollow structure. Composite is a durable material which can be used in place of exotic wood.

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Decking boards

Advantages of composite decking

Comment choisir ses lames de terrasse en bois composite

Composite decking offers a number of advantages compared to pine or exotic wood decking. For example, it is:

  • less expensive than exotic wood;

  • anti-slip;

  • available in different colours;

  • rot-proof;

  • easy to clean and won't wear over time;

  • made to look like wood.

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Wood and composite decking boards

Disadvantages of composite decking

Composite decking also comes with a few drawbacks:

  • it is fairly expensive (around £55 to £100 per square metre);

  • the cheapest composite looks like plastic;

  • the edges of hollow composite can be quite unsightly;

  • the colour of the material can fade over time and through exposure to UV light.

It's best to go for composite that has been coated with a form of UV protection.

Hollow composite decking

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Unlike with solid wood decking, you cannot drill through hollow composite decking boards. These decking boards also tend to be less strong. While hollow composite is less expensive than real wood, you will be able to see the honeycomb profile at the end of the boards. These factors make hollow boards the entry-level choice when it comes to decking.

Solid composite decking

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Solid composite decking boards can look just like real wood as they do not feature a honeycomb profile once cut. They are highly shock-resistant and offer a longer service life than natural wood. The fact that these boards don't feature hollows means that you can drill through the boards wherever you like. However, solid composite decking is more expensive than exotic wood decking. Solid composite decking is therefore deemed a high-end option.

Semi-solid composite decking

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Semi-solid composite decking is just as strong as solid composite. As these boards are not solid, they require fewer raw materials to make and can be about 25% cheaper than solid composite boards as a result. They do feature hollows which makes them less attractive than solid boards if the ends of the boards will be on show. However, it is possible to cap the boards to cover up the ends. Semi-solid decking sits somewhere between solid and hollow composite decking and is considered a mid-range option.

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Wood and composite decking boards

How to select high-quality composite decking

There are four main factors to look out for when it comes to picking out quality composite:

  1. Wood-to-plastic percentage: the higher the wood ratio, the worse the quality as the boards will be more sensitive to humidity and are more liable to warp as the relative humidity changes.

  2. Density refers to the weight of the boards – choose the highest density possible.

  3. Finish: check the surface for staining.

  4. Look out for a long warranty.

If the product specifications do not mention density or wood-to-plastic ratio, look for a low expansion rate which indicates a low wood content and high density.

How much does composite decking cost?


Board type

Wood percentage and density


Price in square metres


Hollow / semi-solid / solid

5 to 10 years

£55 / m²


Hollow / semi-solid / solid

5 to 15 years

£100 / m²


Hollow / semi-solid / solid

5 to 20 years

£150 +

Grooved or smooth decking: what's the difference?

Lame terrasse en bois composite : lames lisses ou lames rainurés

Composite decking is generally anti-slip but, knowing that the weather can affect how slippery it is, it's worth noting that grooved boards will always be more non-slip than smooth boards.

That said, grooved boards are trickier to clean than smooth boards as dirt and water will settle more easily into their grooves.

Composite decking board sizes

Composite decking boards come in all dimensions:

  • Thickness: 18 to 50 mm.

  • Length: 2.2 to 5 metres.

  • Width: 18 to 25 cm.

Composite decking tile formats and sizes


Decking tiles often come in the following dimensions:

  • 20 x 30 cm;

  • 30 x 30 cm;

  • 40 x 40 cm;

  • 50 x 50 cm;

  • 100 x 100 cm.

Decking tiles are made up of several boards which are spaced out and fixed in two or three cross patterns.

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Decking tiles

How to select high-quality composite decking tiles

Pay attention to the five following factors in order to pick out the right decking tiles:

  1. Finish: the boards that make up the tiles must appear uniform. This means they must be level and equally spaced out – there should be no unevenness.

  2. Colours: the boards must be coated with a protective polymer coating.

  3. Strength: the material must remain intact when scraped.

  4. Shape: if you pick hollow boards, the honeycomb structure must be even.

  5. Wood ratio: the higher the wood content, the less durable the decking will be.

Installing decking riser pedestals

The structure and composition of your surface will determine how exactly you can install your decking boards or tiles. If you have a flat and solid surface, such as a concrete slab, you can simply install your decking tiles over the ground or lay joists to which your boards can be secured.

Alternatively, adjustable decking risers can be a great option as they allow you to level your surface without having to carry out too much preparation. Your choice of decking supports depends on whether you are laying decking tiles or boards. Here are the following features to look for when purchasing:

  • polypropylene construction;

  • frost and heat resistance;

  • resistance to cleaning products;

  • able to withstand a minimum load of 1 ton;

  • can be used on grass, asphalt, gravel, etc. ;

  • height adjustments;

  • ability to level a small slope of 5% or more depending on the supports and the type of gap permitted.

The standard BS 585 Part 1 1989 sets out the requirements for decking risers.

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Decking tiles

How to lay composite decking

Composite decking is installed more or less like regular wood decking except when it comes to clipping the boards in place.

7 steps to laying composite decking on decking supports

  1. Prepare the ground so that it is flat and level.

  2. Lay a geotextile membrane to prevent weed growth if installing over a natural surface.

  3. Calculate the number of decking risers required

  4. Position the decking riser pedestals: you'll need 30 risers for 5 m² if you are laying decking boards over joists. If you are laying decking tiles, the number of supports depends on the format of the tiles.

  5. Check that the support is level and factor in a slope of 2% for rainwater drainage.

  6. Lay the decking boards and fit them to your supports or lay and fit your decking tiles.

  7. Fix your boards to the joists using clips.

  8. Cut your composite boards to size.

  9. Fit your deck end caps.

Go for composite decking boards for any installation over concrete and lay your boards parallel to the entrance of the house wherever possible.

How to maintain composite decking

Comment entretenir une terrasse en bois

Composite decking requires doesn't require a lot of maintenance. However, you still need to clean as the seasons change. A broom, water and a special floor cleaning product should be your weapons of choice once spring draws to a close. At the end of winter, it's best to use a slightly harsher product and warm water to clean.

More information on decking

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Guide written by:

Jenny, construction and gardening writer, Oxford

Jenny, construction and gardening writer, Oxford

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