9 min read · Updated 29 August 2026
Composite Decking vs Timber: A Real Comparison
Twenty year costs rather than install prices, plus the slip, heat and expansion issues nobody mentions until the deck is down.
Install cost is the wrong comparison
Timber is cheaper to install and costs you every year. Composite costs more up front and almost nothing afterwards. Over twenty years, which is roughly what a good composite deck should give you, the two converge and composite usually comes out ahead.
| Softwood timber | Hardwood timber | Composite | |
|---|---|---|---|
| Fitted per m² | £90 - £140 | £160 - £260 | £130 - £200 |
| 25m² deck fitted | £2,250 - £3,500 | £4,000 - £6,500 | £3,250 - £5,000 |
| Annual maintenance | £80 - £200 | £60 - £150 | £10 - £30 |
| Lifespan | 10 - 15 years | 20 - 30 years | 20 - 25 years |
| 20 year total, 25m² | £4,500 - £7,000 | £5,500 - £9,000 | £3,700 - £5,600 |
| Fades | Greys without treatment | Silvers naturally | Slight, first year only |
Slip resistance, the real UK issue
Our climate is wet and our gardens are shaded. Smooth timber decking with grooves running the wrong way is genuinely dangerous in November, and grooved boards trap debris which grows algae which makes it worse.
Good composite with a co extruded polymer cap resists algae far better and holds a usable grip when wet. Uncapped first generation composite, which is still sold cheaply, absorbs moisture at the edges and can be just as slippery as timber.
If you go timber, specify smooth reeded boards laid smooth side up and plan on anti slip inserts or strips in the shaded areas. If you go composite, insist on a capped product.
Heat, expansion and the details that matter
Composite gets noticeably hotter than timber in direct sun. On a south facing deck in July, a dark grey composite can be uncomfortable barefoot. Lighter colours reduce it substantially, and it is worth standing on a sample in the sun before choosing.
Composite also expands and contracts with temperature more than wood does along its length. That makes the fixing detail critical: correct end gaps, hidden clips that allow movement, and joist centres at 300mm rather than the 400mm that suits timber. Get those wrong and boards buckle in the first hot spell.
The substructure decides everything
Both materials sit on a frame, and the frame is what fails first on most decks we are asked to replace. Use treated C24 timber at 300mm centres for composite and 400mm for timber boards, on adjustable pedestals or concrete pads rather than directly on soil.
Ventilate underneath. A deck with no airflow beneath it rots from below regardless of what the boards are made of. Leave a minimum 50mm air gap and never enclose all four sides without vents.
Keep the finished deck level at least 150mm below the damp proof course where it abuts the house, exactly as with a patio.
Fire rules, if the deck is on a balcony
For most garden decks there is no fire restriction. If the deck is on a balcony of a building with storeys above 11 metres, building regulations restrict combustible materials, which rules out standard timber and most standard composites.
That only affects a small number of flats and apartments, but if it applies to you it applies absolutely, so check before ordering.
Which we recommend
For a family garden that gets used year round, capped composite in a mid tone, on a treated timber frame at 300mm centres, with proper ventilation. It is the lower total cost and it will not need sanding and oiling every spring.
For a period property, a woodland setting, or where budget is the constraint, good hardwood or well specified softwood laid smooth side up, with an honest conversation about the annual maintenance.
Call 07538 218723 and we will price both for your garden so you can see the twenty year figure rather than just the install figure.
Frequently asked questions
- Is composite decking cheaper than wood?
- Not to install. Composite is £130 to £200 per square metre fitted against £90 to £140 for softwood. Over twenty years composite usually costs less overall because it needs almost no maintenance.
- Does composite decking get slippery?
- Capped composite resists algae well and holds reasonable grip when wet. Uncapped budget composite absorbs moisture at the edges and can be as slippery as timber, so specify a capped product.
- How long does composite decking last?
- 20 to 25 years for a good capped product on a properly built and ventilated frame. The substructure usually fails before the boards do, which is why the frame specification matters.
- Do I need planning permission for decking?
- Usually not, provided the deck is no more than 300mm above ground level and, with other extensions, covers no more than half the garden. Raised decks that overlook neighbours may need permission.