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How to lay composite decking

Planning and preparation

Before you lay your composite decking, it’s important to decide exactly where you want your deck to go and which direction you want your deck boards to run. Very large or raised decks may need planning permission, so be sure to do some research with your local planning office or a qualified decking professional before you go ahead and order your deck boards.

Picking the right spot

Laying decking is a great way to combat tricky areas in your garden such as differing levels, steps down from your back patio doors or uneven ground. Think about the way the sunlight hits the areas of your garden and how that might affect the style of decking, its position and the colour you go for. Avoid darker colours if you have a south-facing garden as they can retain more heat in direct sunlight, making them hotter to walk on for children and pets. On the other hand, if your garden doesn’t get much sun, avoid building your deck under heavy shade-bearing trees that might drop slippery leaves and sap.
Think about the direction you want the deck boards to run in too. Looking along the length of the boards will make the deck look longer, while looking across the boards creates an illusion of width.

Grass, soil or something else?

The structure you decide to lay your composite deck on is almost as important as the deck boards themselves. We’d advise against laying your decking straight onto soft ground such as soil or grass as you may find your decking sinking when the ground gets waterlogged and this will affect its long term performance.

drilling composite decking

The best way to get started is to decide on the location for your deck and measure the length and width of the total area carefully. Using a string line and pegs in the ground is a great way to get a sense of the overall space and make sure it’s big enough both for your furniture and to move around on.
If you’re decking over grass, you should first dig out an area the size and shape of your string line plan, removing a 5cm thick layer of turf. Lay a weed control landscaping fabric over the area to help reduce light reaching the ground and prevent weeds coming up through your decking boards.
Next, build a series of sub-frames for the decking to rest on. You’ll need to angle this to allow for water to run off the decking surface away from your house for example. Ask your decking supplier for advice if you’re not sure what kind of subframe to go for.
Timber is a popular and easy choice, but will eventually rot and need replacing, whilst aluminium is strong and sturdy, but a little more expensive. If you’re expecting your composite decking boards to last a decade, you might as well invest in a joist frame that will last just as long.

Test before building

Before you start constructing your deck, make sure you’ve thought through how you plan to use it day to day. Adding things to your deck after building it such as a hot tub can cause major headaches and need to be carefully planned. A full hot tub can weigh several tonnes, and even soft tubs such as Lay-Z-Spas can reach temperatures of up to 40 degrees. When sited directly onto the surface of a composite deck this can cause the boards under the tub to expand at faster rates than those of the nearby boards which can lead to problems.  A better and simpler hot tub decking option is to build your deck around your hot tub, making sure you leave an easy access point for pump maintenance, etc.

composite decking hollow board
decking board packaging

Using the right products

There are so many options when it comes to choosing the right look and feel for your decking. Cheap softwoods may appeal on price alone, but will need regular treating and maintenance, whilst  hardwoods like teak or pressure-treated timber are more durable, but need to be researched carefully to ensure they are ethically sourced and still need a degree of maintaining to keep them looking at their best.
Composite decking is a mixture of recycled wood and plastic looks and feel like wooden decking but is more or less maintenance free, and aluminium decking is a safe choice for a raised deck or balcony that needs a non-combustible deck.
Your choice will be swayed by your personal design preferences and budget, so it is best to order samples so you can look at your choices up close.

Getting the right tools

Fitting composite decking doesn’t require any different tools to fitting a timber deck, but if your deck shape is going to require a lot of cuts then you’re likely to need a chop or circular saw and a jigsaw as well as the usual sprit level, tape measure and power drill. Avoid the use of an impact driver though as this is not advised for use with composite decking.
Any reputable brand should supply you with a Technical Installation manual with a method to follow, as composite decking fixings usually require a different technique to fitting timber. Usually, the side edges of the composite boards will have a recess in to slide a fastening clip into, which allows for a smooth finish – with no nails or screws in the surface of the board.
All decking needs to be installed with gaps between boards width to width and end to end as they will expand and contract in warmer and cooler weather, so make sure you consult your supplier to check what size gaps you need to leave to avoid buckling or warping.