Composite decking (also known as wood plastic composite, or WPC) is an alternative form of decking built out of composite materials – wood fibres, plastics, and inorganic filler materials. Composite decking can be manufactured to very convincingly imitate the smell, feel and look of wood, but the care, maintenance and cleaning it requires is very different. In most cases composite decks require a lot less effort to maintain than pure timber decks, and for many people not having to oil and stain the deck is one of the main selling points.
Cleaning off dirt
You'll get common surface dirt no matter what sort of decking you choose to install. With composite decking, most manufacturers recommend that you simply wash down your deck occasionally with soapy water and a soft-bristled brush to make sure it's free of any dirt, bird poo or leaves that may build up over time. Others may recommend doing the same, albeit with a purpose-designed composite deck cleaning agent.
This general cleaning doesn't have to be performed obsessively, but it's a good idea to give it a fairly regular clean. If you leave organic build-up like leaves, pollen, dirt and bird droppings for too long on your deck, it can stain your deck and encourage the growth of mould - which is much harder to deal with.
A quick note about high-pressure cleaners: some products can be quickly and easily cleaned using these tools, but they're not always recommended. Check the care instructions provided by your manufacturer before using one on your composite deck.
Unlike PVC decking, wood composite decking is porous and staining can be a quite a problem. Depending on the treatments and what's caused the stain, it may be more difficult to remove a stain from composite decking than it would be to remove a similar stain from a timber deck. If you do drop something like wine or food on your deck, you should try to clean it up immediately with warm soapy water and a brush.
For spot stains that result from something that's been allowed to sit on the deck for a while, first try to remove it with soapy water and a brush. If this doesn’t work, the stain has probably set itself quite well into the pores of the decking. If it's a stain caused by a greasy substance, a degreasing agent may help.
If this doesn't work, you may need to try a commercial composite deck cleaning agent. Most manufacturers and distributors will be able to recommend specific cleaning agents for your deck - and although a mixture of bleach and water may do the trick, it also has the potential to lighten your deck. Some manufacturers may require you to use a particular product in a particular way to protect both the look of the deck, and your warranty.
Composite decking products often come with conditional warranties against staining within a certain number of years - check with your installer or supplier to find out if you're eligible for a replacement under the terms of the warranty.
Composite decking is far more malleable than wood. In manufacturing this is a great thing, because the materials can be easily shaped. Unfortunately, this pliability also makes this type of decking more susceptible to unwanted bending or buckling. Prolonged exposure to harsh sunlight, strong forces or high heat can cause the shape of the materials to change.
You should approach this danger with a philosophy of prevention rather than cure: designers should position their deck away from the direction of the beating sun, or intelligently use roof eaves or other types of shading to shield the deck from the sun’s harsh rays.
How to deal with mould and mildew
Mould is perhaps the biggest problem people tend to experience with composite decking - and in the past, there have even been class action suits filed against decking manufacturers by customers who are unhappy with how readily mould has grown on their decking. Technologies do improve though, and there are ways to clean mould from decking as and when it appears.
Again, prevention is the best cure. Regularly cleaning your deck and dealing with spills as soon as they occur will help to prevent mould on your deck - as will reducing its exposure to constant damp.
If you do get mould on your deck, consult your supplier about the kinds of treatments you can use to deal with it. Most will recommend some type of composite deck cleaner or composite deck wash. In most cases these work best when applied to a dry deck, so that the agent that kills the mould attacks it right down to the root.
Many websites also recommend using a 50/50 mixture of bleach and water to deal with mould. While bleach may be effective in dealing with the mould, it's a fairly strong substance and can also lighten the colour of your deck. Before using this method, check with your decking manufacturer - and only ever proceed after you've tested this mixture on a less conspicuous part of your deck to ensure that it isn't going to spoil the look.
Composite decking delamination
In some cases, excessive or repetitive stress, exposure to extreme heat or UV radiation, or production issues can lead composite decking to flake and disintegrate. This is known as 'delamination'. Delamination is a material failure which affects both the look and the structural integrity of composite decking. Decking that suffers from delamination can't be 'fixed', and in most cases will need to be replaced.