A timber deck costs roughly £50-£100 per m² in materials; composite runs £80-£150 per m². Add £150-£250 per m² for professional fitting, or build it yourself and pay in weekends instead. Here is the honest breakdown.
| Component | Timber | Composite |
|---|---|---|
| Deck boards | £25-£45 | £55-£110 |
| Substructure (joists, posts, pedestals) | £15-£25 | £15-£25 |
| Fixings and screws | £4-£8 | £8-£15 (hidden clips) |
| Frame treatment, weed membrane, gravel | £5-£10 | £5-£10 |
| Total materials | £50-£90 | £85-£160 |
Ranges vary with board grade. Budget softwood boards sit at the bottom; premium grooved or anti-slip timber sits at the top. Composite spreads widest — entry-level hollow boards cost half of solid capped boards.
| Deck size | Timber DIY | Timber fitted | Composite DIY |
|---|---|---|---|
| 3×2m (6 m²) | £350-£550 | £900-£1,600 | £550-£1,000 |
| 4×3m (12 m²) | £600-£1,100 | £1,600-£3,000 | £1,000-£1,900 |
| 6×4m (24 m²) | £1,200-£2,200 | £3,200-£6,000 | £2,000-£3,800 |
| 8×4m (32 m²) | £1,600-£2,900 | £4,200-£8,000 | £2,700-£5,100 |
These assume a straightforward ground-level or low-deck build on a flat base. Raised decks, slopes and multi-level designs add substructure cost faster than board cost — a raised 6×4m deck can double the frame bill.
Pressure-treated timber lasts 10-15 years with cleaning and re-staining every 2-3 years. Composite costs two to three times more but skips the staining and carries 25-year warranties. Over 25 years, two timber decks plus stain roughly equal one composite deck — composite wins if you hate maintenance or plan to stay; timber wins if you might move or want the cheapest route now.
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See also: joist spacing rules, composite vs timber compared, and how many screws you need.