The Short Answer
On our estimates, a softwood deck costs about £70 to £110 per m² supplied and fitted, so £1,050 to £1,650 for a 15m² deck. Hardwood is £110 to £170 per m² and composite £90 to £150. Most decks take one to two days to build.
Height matters twice: raised decks need a stronger frame and steps, and any deck more than 30cm off the ground needs planning permission. For a deck that lasts, the Timber Decking and Cladding Association advises buying decking with a 15 to 25 year performance warranty.
Decking cost calculator
Priced per square metre for the frame and boards, plus height, rails and taking the old deck away.
Estimated total
£1,050 to £1,650
| Treated softwood deck, 15m², frame, boards and fixings | £1,050 to £1,650 |
Decking prices
| Boards | Per m² | 15m² | 25m² | 40m² |
|---|---|---|---|---|
| Treated softwood | £70 to £110 | £1,050 to £1,650 | £1,750 to £2,750 | £2,800 to £4,400 |
| Hardwood | £110 to £170 | £1,650 to £2,550 | £2,750 to £4,250 | £4,400 to £6,800 |
| Composite | £90 to £150 | £1,350 to £2,250 | £2,250 to £3,750 | £3,600 to £6,000 |
What makes a deck last
The Timber Decking and Cladding Association (TDCA) advises:
- choosing products in its DeckMark scheme, or decking with a 15 to 25 year performance warranty, and keeping the paperwork;
- pressure-treated softwood, modified timber or a naturally durable species; since 2020 it recommends that every structural timber (posts, beams and joists) is treated to Use Class 4, whether it touches the ground or not;
- sealing any cut ends with an end-grain preservative, and using corrosion-resistant fixings;
- brushing it regularly, especially in shade, raising plant pots on feet, and checking the whole deck at least once a year.
Extras
| Item | Typical cost |
|---|---|
| Raised frame, per m² | £20 to £50 |
| Steps, each flight | £150 to £400 |
| Balustrade, per metre | £70 to £150 |
| Removing an old deck, per m² | £10 to £20 |
Planning
Decking counts as a raised platform once it's more than 30cm above the ground, and raised platforms aren't permitted development, so a raised deck needs planning permission. Low decks don't. Composite boards are covered in detail on composite decking.
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Frequently asked questions
How much would 15m2 decking cost supply and fit?
On our estimates, about £1,050 to £1,650 in softwood, £1,650 to £2,550 in hardwood and £1,350 to £2,250 in composite.
How much does a 25m2 deck cost?
About £1,750 to £2,750 in softwood or £2,250 to £3,750 in composite, on our estimates.
How much does a 20x20 wood deck cost?
A 20ft by 20ft deck is about 37m², so roughly £2,600 to £4,050 in softwood, on our estimates.
Is it cheaper to do decking or paving?
Softwood decking is about £70 to £110 per m² against £85 to £140 for an Indian sandstone patio, on our estimates, so similar; composite decking costs more.
Do I need planning permission for decking?
Only if it's more than 30cm above the ground. Low decks are permitted development.
How long does decking last?
It depends on the timber, the treatment and the upkeep. The TDCA advises buying decking with a 15 to 25 year performance warranty.
How we priced thisView sources (2, 1 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- OfficialThe Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 1, legislation.gov.uk. Checked 16 Oct 2026.
- IndustryHow long does a timber deck last?, Timber Decking and Cladding Association. Checked 15 Oct 2026.
