Summary
- Installed decks cost $35–90/sq ft (US) or £150–450/m² (UK).
- Composite costs more up front and much less to maintain.
- Foundations, joist spacing and drainage decide the lifespan.
- Raised decks often need permission — confirm before starting.
- Compare quotes on an identical written specification.
Quick answer
A built deck costs roughly $35–90 per square foot in the US and £150–450 per square metre in the UK, including materials and labour. Composite and raised decks sit at the top of the range.
Typical 2026 prices
| Type | US (per sq ft) | UK (per m²) |
|---|---|---|
| Ground-level pressure-treated timber | $35–55 | £150–260 |
| Raised timber deck with railings | $50–80 | £220–380 |
| Hardwood decking | $60–100 | £280–500 |
| Composite decking | $55–95 | £260–480 |
| Steps, per flight | $400–1,200 | £300–900 |
| Railings, per linear unit | $50–120/ft | £90–200/m |
| Demolition of old deck | $5–12/sq ft | £25–60/m² |
A typical 20 m² (roughly 215 sq ft) garden deck therefore lands around £3,500–8,000 or $8,000–18,000.
Timber vs composite
| Pressure-treated timber | Hardwood | Composite | |
|---|---|---|---|
| Material cost | Lowest | High | High |
| Lifespan | 10–20 years | 20–40 years | 25–30 years |
| Maintenance | Annual clean, oil every 1–2 years | Oil yearly to keep colour | Wash only |
| Slip resistance | Good when maintained | Good | Varies — check the grade |
Composite costs more up front and saves maintenance later. Over ten years the totals are closer than the sticker prices suggest.
Foundations matter more than boards
Most failed decks fail underneath. Ask what the quote includes:
Permits and rules
Low ground-level decks usually need no permission, but raised decks, decks over a certain height, and anything affecting a boundary or overlooking a neighbour often do. In the UK check permitted development and any conservation-area rules; in the US check local building codes and HOA rules. Your builder should confirm this in writing before starting.
Comparing quotes
Ask every contractor for the same specification: area, board type, foundation method, joist spacing, railings, steps and finish. Then compare:
Summary
Expect £150–450 per m² or $35–90 per sq ft installed. Spend your money on foundations, joist spacing and drainage detail, not on the most expensive board — that is what decides whether the deck still feels solid in ten years.