What is The Downside of Composite Decking?
Composite decking has real downsides that buyers should understand before committing. It costs more upfront than treated pine, it gets hot in direct sun, it cannot be sanded or repainted, and it expands with temperature changes. None of these are deal breakers for most projects, but ignoring them leads to disappointment.
Table of Contents
Composite Decking Downsides at a Glance
The table below summarises the genuine downsides of composite decking, their severity in Australian conditions, and how each can be managed.
| Downside | Severity | How to manage |
| Higher upfront cost | Moderate | Lower 25 year total cost offsets initial price. AUD $80 to $120/sqm vs $30 to $60/sqm for treated pine |
| Gets hot in direct sun | High in AU | Choose light colours (Silver Grey). On a 35°C day, light boards reach ~55°C vs ~64°C for dark |
| Expansion and contraction | Moderate | Leave 5 to 8 mm end gaps and 10 mm perimeter gaps per EVODEK installation guide |
| Colour fading over time | Low (co extruded) | Co extruded cap layer slows fading. Grey tones show less visible change than dark browns |
| Cannot be painted or sanded | Low | Choose colour carefully upfront. Use the Colour Selector and order free samples |
| Mould in humid conditions | Moderate in AU | Ensure airflow beneath deck. Clean with soapy water quarterly in humid climates |
| Looks different from timber | Subjective | EVODEK Ultra Grain surface creates deeper wood texture than flat moulded boards |
Composite Decking Gets Hot in Direct Sunlight
On a 35°C day in full sun, light grey composite boards typically reach 50°C to 55°C at the surface, while dark boards can exceed 60°C. Surface temperature is the most significant composite decking downside in Australia because of the country’s high UV levels and long summer days. These temperatures make barefoot walking uncomfortable during peak sun hours.
Board colour controls the temperature more than material type. A dark-stained Merbau timber deck and a dark composite deck in the same location will reach almost identical peak temperatures. Choosing EVODEK Silver Grey or Silver Birch is the most effective single step for managing surface heat on a north or west-facing deck. For help selecting between grey tones, see which grey composite decking is best for you.
Composite Decking Costs More Upfront Than Timber
Composite decking materials cost approximately AUD $80 to $120 per square metre, compared to AUD $30 to $60 per square metre for treated pine. Including installation, the gap narrows because composite boards use hidden clip systems that are faster to install than face-screwing timber.
Over 25 years, composite decking typically costs less in total because it eliminates sanding, staining, and sealing every two to three years. A 30 sqm treated pine deck costs approximately AUD $7,500 to $13,500 over 25 years, including maintenance, while the same area in EVODEK composite costs approximately AUD $4,400 to $7,700.
Learn More: Comparison of Composite Decking vs Wood Cost
Composite Boards Expand and Contract with Temperature Changes
EVODEK boards require 5 to 8 mm expansion gaps at board ends and a minimum 10 mm perimeter gap to prevent buckling. All composite decking expands and contracts as temperatures change. Boards installed on a cool day (below 15°C) need the larger end gap because they will expand more during summer.
Most expansion problems I see in project reviews result from gaps that were too small or were filled with rigid sealant. When a board cannot move, it buckles at the weakest point, usually a butt joint. Correct gap sizing eliminates this issue. For detailed gap requirements by climate zone, see can you install composite decking without gaps.
Composite Decking Colour Fades Gradually with UV Exposure
Most composite decking shows its greatest colour change within the first 12 to 24 months of outdoor exposure, then stabilises. Capped composite decking, such as EVODEK fade significantly less than uncapped or first-generation composite boards. This is because the protective cap layer contains UV stabilisers.
Grey tones show less visible fading than dark brown or red tones because grey is already close to the natural weathered appearance of most outdoor materials. Darker colours fade more noticeably. This is worth considering when choosing your board colour. Use the EVODEK Colour Selector to preview colours and order free samples to see them in your outdoor light before committing.
Other Downsides to Consider
Three additional downsides affect fewer buyers but are worth understanding before purchase:
- The inability to repaint
- Mould risk in humid climates
- The visual difference from natural timber
Composite Decking Cannot Be Painted or Sanded After Installation
Unlike timber, composite boards cannot be sanded smooth if scratched or repainted if you want a different colour. The colour is integral to the board. This means your colour choice is permanent. If a board is badly damaged, it must be replaced rather than repaired in place.
Mould Can Grow in Humid Conditions
Mould and mildew can grow on any outdoor surface in humid Australian climates, including composite decking. The mould grows on surface debris, not the board material itself. Ensuring adequate airflow beneath the deck, keeping board gaps clear of leaves and dirt, and washing the composite deck with soapy water quarterly will prevent most mould issues.
Composite Decking Looks Different from Natural Timber
Composite boards are more uniform in colour and grain pattern than natural timber. Some homeowners prefer the organic variation of real wood. EVODEK boards use Ultra Grain surface technology to create a deeper and more varied wood texture than flat moulded composite boards, but the material will never be mistaken for natural hardwood up close. Requesting free samples and placing them next to your existing timber is the best way to judge whether the appearance meets your expectations.
Conclusion
Composite decking has genuine downsides: higher upfront cost, surface heat in direct sun, expansion movement, gradual UV fading, and inability to be sanded or repainted. In Australian conditions, surface temperature and mould are the two most relevant concerns. All of these downsides can be managed through informed colour selection, correct installation gaps, adequate subframe airflow, and realistic expectations about long term appearance.
EVODEK composite boards with a 25 year residential warranty and 10 year commercial warranty address the durability and fading concerns better than uncapped boards. Request a quote from your nearest Australian distributor, or visit the EVODEK DIY Solutions guide for installation best practices.
FAQ
What is the biggest downside of composite decking in Australia?
Surface temperature in direct sunlight is the most significant downside in Australian conditions. On a 35°C day, composite boards in full sun can exceed 55°C to 60°C depending on colour. Choosing a light coloured board, such as EVODEK Silver Grey, and adding shade are the most effective ways to manage this.
Does composite decking fade in colour?
Yes, all composite decking experiences some gradual colour change due to UV exposure. Capped composite decking boards fade less than uncapped boards because the cap layer contains UV stabilisers. Grey tones show the least visible change. Darker colours fade more noticeably, but the structural performance is not affected.
Is composite decking more expensive than timber?
Composite decking costs approximately AUD $80 to $120 per square metre for materials, compared to AUD $30 to $60 for treated pine. However, timber requires sanding and restaining every two to three years, which adds AUD $3,000 to $5,000 or more over 25 years. Composite typically costs less in total over the life of the deck.
Can you paint or sand composite decking?
No. Composite decking colour is embedded during manufacturing and cannot be changed by painting or staining. Scratches cannot be sanded out as they can with timber. This makes the initial colour choice important. Use the EVODEK Colour Selector and order free samples to confirm your choice in your actual outdoor conditions before ordering.
Does composite decking get mouldy?
Mould can grow on composite decking surfaces in humid Australian climates, particularly in shaded areas with poor airflow. The mould grows on surface debris, not on the board material itself. Quarterly cleaning with soapy water and keeping gaps clear of leaves prevents most mould issues. Co extruded boards resist moisture absorption, which reduces the conditions that support mould growth.
How much does composite decking expand?
Composite boards expand and contract with temperature changes. EVODEK specifies end gaps and perimeter gaps in its installation guide to allow for this movement. Boards installed on cool days need larger gaps than those installed in warm weather. Correct gap sizing prevents buckling and warping.
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