So, what is Composite Decking?
Invented in the late 1980s, wood-plastic composite decking (also called “composite wood decking”) is made of wood fibres encased in plastic. Composite decking is readily available at big box home improvement stores like Floors to Walls as well as local lumber yards throughout the UK. Many homeowners choose wood decking because it is familiar, readily available and affordable. At the same time, wood decking comes with problems like splinters, rot and high maintenance. Although composite wood decking is easier to maintain, some homeowners worry that composites won’t look as nice as wood.
What are the problems of Composite Decking?
When a wooden deck loses its colour, you can easily recolour it with paint. If you decide that you want a different theme for your garden, you can grab a bucket of paint and repaint a wooden deck. And the best thing is, you can select any colour you want. Unfortunately, you can’t do the same for composites. Once you choose the colour, you have to stick with that colour. If you do want to paint the composite deck, you have to sand it first. Not doing so will only chip off the paint. However, if you do wish to paint a composite deck and sand it beforehand, it damages the boards and loses protection. If you like to repaint decks, composites may not be the best for you. However, there are a few reasons to repaint a composite deck on the bright side. They are long- lasting and are not easily damaged or chipped. Unlike wood, it doesn’t fade to grey when exposed to UV. Instead, it only lightens the colour of the material.
Here's the advantages
In order for a deck to be worth the cost, it needs to be durable. Plus, if it’s going to be the location of many family gatherings, it needs to be ultra strong to bear the weight of people, furniture, and family pets. You can expect this with a composite deck, as they are constructed out of multiple materials for exceptional strength and resistance to wear and tear over the years.
Since composite decking won’t break down and rot over time like wood, it requires little upkeep. It doesn’t even need to be restained or repainted! You’ll most likely just need to hose it down or power wash it occasionally to keep it looking its best. No trees are harmed in the making of composite decks! Since a majority of them are made from recycled or scrap materials, there is virtually no environmental impact—especially compared to wood decks which require a decent amount of lumber.
So how do I install Composite Decking?
How to prepare
An existing patio or concrete base can be used as a solid foundation for your deck. Start by measuring and marking out the required area. If you’re laying your deck over the lawn then mark out the area using pegs and builders line. Use a straight edge to cut the edges, then remove the turf and dig the soil out to a depth of 50mm.
Cover the ground with landscaping or weed control fabric and weigh it down with gravel or pea shingle. If you’re laying on soft ground then place paving stones on top of the gravel – these will properly support the joists and preserve the timber. Use a spirit level to make sure the stones are all on the same level.
How to build the frame for the composite decking
To join up your joists start by measuring and cutting the section you need to reach the required length. Measure and cut a separate section 600mm in length, and then mark its centre point at 300mm. Secure the three sections in your workbench and make sure that the 300mm mark lines up with the join of the joists.
You now need to measure and mark four guidelines on the joists. Measure and mark a spot 75mm from each side of the join. Then measure and mark another spot 150mm from each side of the join. Use a set square to draw a straight vertical line through each of the four marks.
Mark two evenly spaced pilot holes into each of the lines you have drawn. Drill pilot holes with a 6mm wood drill bit and secure the joists together using 100mm screws. Countersink the screws if you will be using fascia boards. The joist is now ready to move into position.
Put your joists into position with any extended joists at the end where there will be the least through traffic. If the sides of your frame will be hard to access, you may have to assemble the complete frame before asking a friend to help you move it into its final position.
Use a set square to check that the corners are square. Then mark and drill pilot holes before using two 150mm timber screws to fix the corners together. Countersink the screws if you will be adding a fascia.
The decking frame should now be at the right level. Use risers, paving slabs or treated offcuts of timber at 500mm intervals to help with this, and check with a spirit level.
Assembling the inner joists
The positioning of your internal joists will be dependent on the design you have chosen for your composite decking. Here we are laying our boards horizontally, so our joists need to be spaced at 300mm intervals.
Measure and mark out the positioning of the joists onto the frame, making sure you don’t exceed the recommended spacing. Then measure and cut your joists accordingly.
Using a set square, extend your mark down the external face of the frame and mark two pilot holes, one 40mm from the top of the frame and one at 40mm from the bottom. Drill the pilot holes using a 6mm wood drill bit. Drill countersink holes if you are going to add a fascia.
Secure a joist in your workbench and attach joist hangers to both ends using 30mm external grade screws.
To secure the joist to the frame, place it into position so the centre of the joist lines up with the spacer mark. The joist end must be flush with the exterior frame, so either use packers to keep it in place, or ask someone else to help. Secure the joist using 100mm timber drive screws.
If you have to secure the joist onto an unexposed side of the frame then drill a skewed pilot hole at a 45 degree angle, then fix with a 100mm timber drive screw.
Once all the internal joists are in place, add the final 30mm screws to each joist hanger.
Fixing the noggins into place
Mark the centre of the noggin’s position on each joist and use a set square to draw a vertical line down the joist. Then measure and mark two pilot holes on each line, 40mm from the top and 40mm from the bottom.
Drill pilot holes before securing the noggin with 100mm external timber drive screws. Once all the noggins are in place, check that your frame is level, and all your fixings are secure.
Now let's lay the composite decking
Now your timber frame is complete you can lay your composite deck boards. If you have no overhang or you have a fixed deck, begin by fitting starter clips along the outer edge of the frame. Secure these clips with the screws and drill bit provided.
For our decking we are working with an overhang. Put your first board into position, making sure the overhang is no more than 25mm. If you will be adding a fascia, place an offcut of board underneath the overhang to ensure the edges will be flush with each other.
Measure in 30mm from the edge of the board and drill a pilot hole using a 4mm drill bit. Repeat this process down the length of the board, then fix the board using composite deck screws.
With the first board in position, slide the hidden fastener clip into place so it sits within the groove of the deck board, and directly in the centre of the joist beneath. These fasteners are used to secure the deck boards and ensure a consistent 6mm expansion gap.
Tighten the clip until it’s about 75% secure – there’s no need to fully tighten it just yet. Repeat this process down the length of the decking board so there’s a fastener clip at every joist.
Put the next board into position so that the fastener clips sit within its groove. Try not to push or force the board. Then repeat the above process, adding a new set of fastener clips for this second board.
Once the second board is 75% secure you can finish tightening the screws in the first row. Repeat this process for each successive decking board you lay down. Remember to lay down the next board before fully tightening the screws on the previous board.
If you are adding a fascia board, start by measuring and marking 40mm in from each end of the board, then use a chalk line to connect the marks. Using the chalk line as a guide, mark at 300mm intervals down the length of the board.
Drill your pilot holes and put the fascia board into position, ensuring a 40mm ventilation gap between the bottom of the board and the ground. Place packers underneath the fascia or ask someone to hold it level whilst you fix it to the frame. Then secure the fascia with 63mm composite decking screws.
Butt joins
If you need two deck boards to meet end to end this will create a “butt” joint. All butt joints must sit on doubled up support joists that have a drainage gap of 10-25mm between them. Secure with four fastening clips, two at each end of the board, being sure to leave the recommended expansion gap between boards. Try and get the fastening clips as close to the edge of the boards as possible, as this will help the edges of the boards to look even.
