11th Apr 2023 -

As we approach the warmer months, incorporating garden decking into your outdoor space is an attractive and functional addition. While timber decking has been the traditional decking of choice for years, composite decking has emerged as a popular alternative due to its exceptional strength and durability. As you explore decking options and plan for its installation, we encourage you to consider composite decking. In this article, we will provide an overview of what you need to know about fitting composite decking.

What is composite decking?

Created from a combination of bonding agents, wood fibres and plastics, composite decking is a low-maintenance alternative to traditional timber decking. Although composite decking can cost more than timber decking initially, it will last longer and require less maintenance which makes it cheaper long term. Because of the materials it is made from, composite decking is resistant to dampness and rot and is also durable. The composite boards and composite tiles do not need to be stained or sealed for further protection against weather elements. Unlike timber decking, composite decking does not crack or warp in direct sunlight - it also absorbs minimal water from rainfall or spillages.

How to fit composite decking

To ensure a successful installation of composite decking, there are 12 steps that you should follow. As you plan for the project, it's important to consider the climate and allow for the acclimatisation of the decking boards or decking tiles. This typically takes around three days and involves laying each tile or board on sheets and covering them in the garden. This process will help the decking adjust to the weather conditions and ensure optimal performance over time.

Step 1 - Gather tools and materials

While leaving the composite decking to acclimatise, you should collect all tools and materials you will need throughout the job.

Composite decking boards or tilesTimber
Hammer and spirit levelMitre saw or handsaw
Tape measureComposite joists
Googles and pencilCordless drill and 6mm drill bit
Composite decking trimGloves
Decking screwsExterior nails
Cordless screwdriverReady-mixed concrete
Sand or pea shingleWeed membrane/landscaping fabric
Straight edge (set square)Builders line
Decking (fastener) clipsJoist hangers

Step 2 - Prepare the ground

Using your tape measure, start to map out the composite decking area. If you plan to lay your deck boards or tiles on your lawn, be sure to use a builders line and pegs to mark out the area. Cut any edges using a straight edge, then dig the soil at a depth of approximately 50mm. With landscaping fabric or weed membrane, cover the ground and secure it with pea shingle. For laying tiles or deck boards on soft ground, paving stones will need to be placed on top of the pea shingle to reinforce the joists and protect the timber. Make sure to use a spirit level to check everything is even. 

Step 3 - Build the composite decking subframe

Composite decking subframe being built in a back garden with a timber structure.

For the decking frame, join 2 sections together. This should be done if the decking is longer than the decking joists. To do this, measure and cut each section to reach the length you need. With a separate section, cut this to a length of 600mm - a halfway centre point line should be marked at 300mm. Then on your workbench, secure all 3 sections so the join of the joists and the 300mm mark are aligned. 

Step 4 - Mark out joist guidelines

On the joists, you will next need to mark out 4 guidelines. Use your tape measure to mark out a spot 75mm from each join side, then a further spot 150mm from the join sides. Draw a vertical straight line with a straight edge - the line should go through the 4 guideline marks. Once the line is drawn, pilot holes will need to be evenly marked out. With a 6mm bit, drill the pilot holes and use 100mm screws to secure the joists.

Step 5 - Position composite decking joists

After you have drilled the pilot holes, place the joists in the correct position. Extended joists should be at the end. With your set square, double-check that all corners are square and drill pilot holes with two 150mm screws to secure them. Once this is completed, the composite decking framing should now be fixed at the correct level - use your spirit level to go over this. 

Step 6 - Collect internal joists

Your internal joists should be spaced at 300mm intervals. Using a tape measure and pencil, mark the joist spacing for composite decking onto the frame and be careful not to go over the 300mm spacing. Once the spacing is marked, cut the joists and use a set square to lengthen the mark down the frame’s external face with 2 pilot holes. Both should be 40mm from the top and bottom of the frame - the holes need to be drilled using the 6mm drill bit from Step 4. 

Step 7 - Secure the joists

At your workbench, secure a joist so the decking spacers and middle of the joist are aligned. Fix joist hangers at each end with 30mm external grade screws, and be sure to check the joist end is flush with the frame exterior. Use 100mm timber screws to secure the joist. If you are securing a joist onto the frame’s unexposed side - at a 45-degree angle - drill a skewed pilot hole and fix it together with 100mm timber screws. After everything is in place, fix 30mm screws to the joist hangers.

Step 8 - Secure the noggins 

When you secure the noggins, pinpoint the middle of the noggin position on every joist. Be sure to use a set square to draw a line vertically down the joist. On each line, you will need to mark 2 pilot holes: the first should be 40mm away from the top; the second should be 40mm from the bottom. Drill the holes and fix the noggins with the help of 100mm external timber drive screws. Once you have placed the noggins, make sure to check the decking frame is level. 

Step 9 - Fix the composite decking

After you have built the frame, now is the time to lay the composite decking boards or tiles. For decking with no overhang, drill screws along the frame’s outer edge. Drilling screws will secure the clips in place. Place your first tile or board into position - if there is an overhang, make sure it does not go over 25mm. For adding a fascia, a composite decking offcut should be fixed under the overhang - this will make sure all edges are level and flush with one another. From the edge of the tile or board, drill a pilot hole 30mm from the edge. Secure the hole with a composite deck screw and repeat the process down the tile or board length. 

Step 10 - Place composite decking clips

Once the first tile or board is fixed, place a composite decking (fastener) clip so it is within the tile or deck board groove, in the centre of the joist underneath. Be sure that each fastener clip is secure at around 75% - you will need to tighten them later on fully. Carry on the process so a fastener clip is placed at each joist. Within the groove of the second board or tile, place the fastener clips but try not to force or push the board. 

Step 11 - Finish tightening the clips

After the fastener clips on the second tile or board are 75% secure, return to the first and fully tighten the clips. Make sure to fully tighten the previous tile or board clips before installing the next one. For adding a fascia board, measure and mark 40mm from each tile or board end and connect the marks using a builders line to act as a guide. Along the length of the tile or board, mark 300mm interval gaps. 

Step 12 - Fit fascia boards

Builder drilling a fascia board on composite decking with a yellow drill.

You can add composite decking trim to finish off any edges. But if you are fitting fascia boards, drill pilot holes and place the fascia board into its correct position. Ensure to leave a ventilation gap of 40mm between the ground and the bottom of the tile or board. With packers, place them under the fascia and secure the fascia with composite decking screws. Then you will need to drill 2 evenly spaced pilot holes on each of the drawn lines and use 100mm timber drive screws to secure. 

Can you paint composite decking?

Because composite decking colours are added when boards and tiles are manufactured, you do not need to paint the decking. This added colour is designed to be durable and last for many years. If you were to paint your decking - whether you choose a neutral light grey or traditional coffee brown shade - you run the risk of the paint chipping and flaking over time because of the year-round weather elements. Also, because of how composite boards and tiles are constructed, painting them will likely result in an untidy appearance.  

How long does composite decking last?

On average, you can expect your decking to last between 25-30 years. Whereas timber decking has an estimated lifespan of 10-15 years. The mix of plastics, bonding agents and wood fibres helps to boost the lifespan of composite decking, creating a protective barrier against wear and tear and harsh weather. 

Composite decking materials with UK-wide delivery

If you plan on laying composite decking in your garden and you have decided on composite decking boards or tiles, we can supply a wide variety of materials from Cladco composite decking tiles to composite decking fixings. Explore our range and shop competitive composite decking prices. For builders and construction professionals, we also provide trade accounts. As one of the UK’s leading building and construction suppliers, you gain access to your knowledgeable trade account manager who will help you source the finest tools and materials at the best trade price and organise speedy UK delivery. Call the team to find out more or sign up for an account on our website.