Decking Cost Calculator
Decking is one of the most popular garden projects in the UK, giving you a level, low-maintenance space for furniture and entertaining without the ongoing work of a lawn. The material you choose makes a big difference to both the upfront cost and how much maintenance you'll be doing every year — budget softwood is cheapest to install but needs regular treatment, while premium composite costs more up front but needs very little upkeep for decades. Enter your deck dimensions below to get an estimated fully installed cost range for each material.
Enter your deck dimensions
We'll estimate the fully installed cost based on your chosen decking material.
Deck area: 12.0m² with Pressure-treated softwood (budget) at £80-120/m² installed (materials + labour):
£960 - £1,440 estimated total
This is a fully installed estimate (decking boards, joists, fixings and labour). Actual costs vary with substructure, ground preparation, deck height, balustrades and your local tradesperson's rates.
Compare materials for this area
- Pressure-treated softwood (budget)£960 - £1,440
- Hardwood (mid-range)£1,440 - £2,160
- Composite (premium)£1,800 - £3,000
Recommended for your patio
Furnish your new deck with a few well-reviewed garden furniture options.
- Rattan
- Patio dining
Currently unavailable
Pros
- All-weather PE rattan weave
- Rising table with built-in ice bucket
- Showerproof, UKFR-compliant cushions
Cons
- Heavy — needs two people to move
- Premium price for the corner + footstools configuration
- Rattan
- Balconies & small patios
£299.99
Pros
- Compact — fits small patios and balconies
- Removable, machine-washable cushion covers
- Glass-top coffee table with storage shelf
Cons
- Cushions fade after a season in direct sun
- Resin
- Balconies & small patios
£170.00
Pros
- Fully weatherproof resin, rattan-effect weave
- Built-in storage table doubles as a coffee table
- Compact size ideal for balconies
Cons
- Seats two only
- No cushions included as standard
Frequently asked questions
Do I need planning permission for decking?
Most garden decking in the UK falls under permitted development and doesn’t need planning permission, provided it’s no more than 30cm above ground level, covers no more than 50% of your garden together with other outbuildings, and isn’t in front of the house. Raised decks over 30cm or decking near a boundary in a flat or maisonette may need a check with your local council.
Composite vs wood decking — which lasts longer?
Composite decking typically lasts 25-30 years with minimal upkeep, resisting rot, splintering and colour fade far better than timber. Pressure-treated softwood needs re-staining or oiling every 1-2 years and generally lasts 10-15 years, while hardwood can last 20+ years but needs regular oiling to keep its colour and prevent cracking.
What is included in the installed cost estimate?
Our estimates cover decking boards, the joist substructure, fixings and standard labour for a straightforward ground-level deck. They don't include extras like raised sub-frames on sloped gardens, balustrades and steps, groundwork or drainage, which can add significantly to the final price.
Why is composite decking so much more expensive than wood?
Composite boards cost more upfront because they're made from recycled wood fibres and plastic bonded under pressure, which is a pricier manufacturing process than sawn timber. That cost is usually offset over time by near-zero maintenance — no annual staining or oiling — and a much longer lifespan than softwood.
How this calculator works
The calculator multiplies your deck length by width to get the total area in square metres, then applies a fully installed price range per square metre for the material you choose. The estimates include decking boards, joist substructure, fixings and standard labour for a straightforward ground-level deck. They don't include extras like raised sub-frames on sloped gardens, balustrades, steps, groundwork or drainage, which can add significantly to the final price.
The three material bands are based on typical UK installed prices: pressure-treated softwood at £80-120/m², hardwood at £120-180/m², and composite at £150-250/m². These are rough guides only — actual prices vary by region, supplier, site access and the complexity of the job. Always get at least three quotes from local installers before committing.
UK decking materials compared
| Material | Installed cost per m² | Lifespan | Maintenance | Best for |
|---|---|---|---|---|
| Pressure-treated softwood | £80-120 | 10-15 years | Annual staining/oiling | Budget projects, low-level decks |
| Hardwood (e.g. ipe, cumaru) | £120-180 | 20+ years | Annual oiling | Premium look, high-traffic areas |
| Composite (wood-plastic) | £150-250 | 25-30 years | Minimal — wash only | Low-maintenance, families, elderly |
| PVC / vinyl | £180-280 | 30+ years | Minimal | Marinas, pool surrounds, commercial |
Worked example: A 4m x 3m deck
A deck 4m long and 3m wide has an area of 12m². Using pressure-treated softwood at £80-120/m² installed, the estimated cost is 12 × £80 = £960 to 12 × £120 = £1,440. Hardwood would be £1,440-£2,160, and composite would be £1,800-£3,000.
These are fully installed figures. If you're DIYing the job yourself, material-only costs are roughly 40-50% of the installed price. For the same 12m² softwood deck, materials alone might cost £400-£600, with labour saved if you do it yourself. However, factor in tool hire, sub-frame materials and the time cost — a straightforward 12m² deck typically takes two people 2-3 days to build.
Common mistakes when planning decking
- Building too close to the ground. Decking needs ventilation underneath to prevent rot — leave at least 150mm of clearance between the bottom of the joists and the soil. If the ground is damp or prone to waterlogging, use concrete or plastic deck supports to raise the frame higher.
- Skipping the sub-frame. The joist substructure is what holds the deck up and prevents bounce. Skimping on joist size or spacing (more than 400mm centres for softwood, 300mm for hardwood) leads to a bouncy, uneven deck that won't last.
- Not accounting for drainage. A flat deck with no fall will pool water in wet weather, which accelerates rot and makes the surface slippery. A slight fall of 1:80 away from the house is standard, or use a drainage channel at the low point.
- Choosing the wrong fixings. Stainless steel or coated screws are essential for outdoor use — ordinary steel screws will rust and stain the timber within a year. Composite decking usually needs special hidden clips or screws designed for the material.
- Forgetting building regulations for raised decks. A deck over 30cm above ground level may need building regulations approval if it's attached to a house or has balustrades. Check with your local council before starting, especially if the deck is near a boundary.
What to look for when buying decking
For softwood, look for pressure-treated timber with a guarantee against rot and insect attack. The preservative should be pressure-impregnated (marked as Tanalised or similar) rather than just surface-sprayed. Check that the boards are graded for outdoor use — some softwood is only suitable for indoor joinery and will rot quickly outside.
For hardwood, check the species and its suitability for UK climates. Tropical hardwoods like ipe and cumaru are durable and dense, but they're heavy to work with and require pre-drilling for screws. Some hardwoods, like oak, are also available from European or UK sources and can be a more sustainable choice.
For composite decking, look for a product with a UV-stabilised cap to prevent fading, and check that the hollow or solid board construction is rated for the span you need. Hollow boards are cheaper but can be less rigid and more prone to flexing. A good composite deck should come with a 25-year residential warranty against rot, staining and fading.
More questions answered
Do I need planning permission for decking?
Most garden decking in the UK falls under permitted development and doesn't need planning permission, provided it's no more than 30cm above ground level, covers no more than 50% of your garden together with other outbuildings, and isn't in front of the house. Raised decks over 30cm or decking near a boundary in a flat or maisonette may need a check with your local council.
Composite vs wood decking — which lasts longer?
Composite decking typically lasts 25-30 years with minimal upkeep, resisting rot, splintering and colour fade far better than timber. Pressure-treated softwood needs re-staining or oiling every 1-2 years and generally lasts 10-15 years, while hardwood can last 20+ years but needs regular oiling to keep its colour and prevent cracking.
What is included in the installed cost estimate?
Our estimates cover decking boards, the joist substructure, fixings and standard labour for a straightforward ground-level deck. They don't include extras like raised sub-frames on sloped gardens, balustrades and steps, groundwork or drainage, which can add significantly to the final price.
Why is composite decking so much more expensive than wood?
Composite boards cost more upfront because they're made from recycled wood fibres and plastic bonded under pressure, which is a pricier manufacturing process than sawn timber. That cost is usually offset over time by near-zero maintenance — no annual staining or oiling — and a much longer lifespan than softwood.
Can I build a deck on uneven ground?
Yes, but it's more complex and expensive. On a slope, you'll need a raised sub-frame with adjustable deck supports or a stepped design. The ground must still be stable — if it's prone to movement or waterlogging, you may need foundations or a retaining wall first. Get a site survey before designing a deck on a steep or uneven plot.
How long does it take to build a deck?
A straightforward 12-20m² deck built by a small team typically takes 2-3 days for construction, plus a day for any staining or oiling if you choose timber. Larger or more complex decks — with steps, balustrades or multiple levels — can take 1-2 weeks. DIY builds usually take longer, especially if you're learning as you go.
Should I seal or stain my timber deck?
Yes — a good quality decking oil or stain applied annually (or every two years for some products) protects the timber from UV damage, moisture and mould, and keeps it looking fresh. Composite decking doesn't need sealing, but you can wash it with soapy water or a specialist cleaner to remove algae and dirt.
What's the best direction to lay decking boards?
Lay boards perpendicular to the house for a clean, balanced look, and always leave a 5-8mm gap between boards for drainage and expansion. If the deck is on a slope, lay the boards level across the joists rather than following the slope — this prevents water pooling and makes the surface safer to walk on.