How to Price Decking: Softwood, Hardwood, Composite Labour and Materials Guide

Quick Answer: A typical UK garden deck in 2026 prices £55–£95 per m² supply and fit for treated softwood pine, £140–£260 per m² for hardwood (iroko or balau), and £120–£220 per m² for composite (PVC or wood-fibre). Most 20–30 m² gardens take 3–5 days on site for a fitted deck on a level base, with sub-frame, posts, balustrade and steps priced separately. Building Regulations Part K is triggered where the deck surface sits more than 600 mm above adjacent ground — at that point a 1100 mm balustrade, properly load-bearing, becomes mandatory.

Summary

Decking is the most price-variable of the common UK garden trades. Two decks of identical surface area can quote at £1,800 and £8,500 — both legitimate — because the sub-frame, ground prep, balustrade detailing, post foundations and choice of board separate them. A flat lawn-level softwood deck is a different job from a raised composite deck with hardwood balustrade and powder-coated steel posts. Pricing accurately means breaking the quote into seven discrete components: ground prep, sub-frame, posts and pads, decking boards, fixings and trims, balustrade and steps, and labour.

The dominant choice for new UK domestic decking has shifted toward composite in the past five years. The maintenance gap is the driver — softwood needs annual cleaning, biennial oiling, and re-staining every 3–4 years, while composite is hose-down only. On a 20-year horizon, composite at £180/m² often beats softwood at £75/m² once homeowner labour or tradesperson maintenance contracts are added. That long-horizon argument is now widely understood by clients and a quote that doesn't address it loses to one that does.

The most under-priced quote item is the sub-frame. A correctly built deck uses Class 4 treated softwood joists at 4×2 (95 × 45 mm) at 400 mm centres maximum, on Postcrete-set posts or concrete pads, over a weed-suppressing membrane on a stone base. Quotes that show only the deck boards as a unit rate and bury the sub-frame in "labour" mislead the homeowner and reliably under-cost the job. A 25 m² deck has roughly 100–140 linear metres of joist plus 6–10 posts — that's £350–£700 of timber on its own.

Key Facts

Quick Reference Table

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Deck specification 15 m² fitted 25 m² fitted 40 m² fitted Programme
Treated softwood, ground-level, no balustrade £1,200–£2,000 £1,800–£3,000 £2,800–£4,800 2–4 days
Treated softwood, raised 400 mm, with steps £1,800–£2,800 £2,600–£4,200 £4,200–£6,800 4–6 days
Treated softwood, raised 800 mm + balustrade + steps £2,800–£4,500 £4,200–£6,500 £6,500–£10,500 5–8 days
Composite, ground-level, no balustrade £2,000–£3,200 £3,200–£5,200 £4,800–£8,500 3–5 days
Composite, raised 400 mm, with steps £2,800–£4,500 £4,200–£6,800 £6,500–£10,500 5–7 days
Composite, raised 800 mm + balustrade + steps £4,000–£6,500 £6,200–£9,800 £9,500–£16,000 6–10 days
Hardwood (iroko), raised 400 mm, with steps £3,200–£5,200 £5,000–£8,000 £8,000–£13,000 5–7 days
Hardwood + steel-cable balustrade, raised 800 mm £5,500–£9,000 £8,500–£14,000 £13,500–£22,000 7–11 days
Aluminium deck on ground screws, no balustrade £3,500–£5,500 £5,200–£8,500 £8,000–£13,500 4–6 days

Detailed Guidance

Choosing the Board: Softwood, Hardwood or Composite

The board is the most visible decision but rarely the largest cost line on a complex deck. For pricing:

Treated softwood (Scandinavian or Baltic pine, pressure-treated to Use Class 3) — £18–£32 per m² supplied. Standard groove pattern. 15–20 year design life. Needs annual brush-down, biennial oil, 3–4 yearly stain. Weathers from honey to silver-grey unless maintained. Cheapest option, lowest spec, highest ongoing labour for the homeowner.

Hardwood (iroko, balau, ipe, garapa) — £55–£140 per m² supplied. Genuine premium product. 25–40 year design life if maintained. Iroko is the most common UK choice — denser than pine, sustainable when FSC-certified, weathers to silver if untreated. Ipe is the dense Brazilian option — almost stone-hard, requires pre-drilling, premium price. Balau is a mid-tier hardwood at sub-iroko price.

Composite (PVC + wood-fibre, capped or uncapped) — £45–£90 per m² supplied. The dominant new-installation choice. Capped composite (a co-extruded outer skin over a core) is mainstream now — better stain resistance, fade resistance, less prone to mould than first-generation uncapped boards. Trex, Millboard, Trex Transcend, Composite Prime and similar dominate UK supply. 25-year manufacturer warranty common.

Aluminium — £80–£160 per m² supplied. Niche but growing. Powder-coated, anti-slip ribbed top, drainage channels integral. Used where fire spread regulations matter (above habitable space, near boundaries) or where wood-look is rejected.

Ground Prep and the Sub-Frame

The sub-frame is the structural backbone and the line item most likely to be misquoted. A deck sub-frame for a 20–30 m² deck consists of:

Ground membrane — woven polypropylene weed membrane laid on prepared ground. Stops grass and weeds growing under the deck. £2.20–£3.80 per m² supplied; 1–2 hours to lay across a typical deck footprint.

Stone base (where decking is at ground level) — typically 50–100 mm of MOT Type 1 or 20 mm crushed stone over membrane to allow drainage. £35–£65 per m² supplied and installed.

Posts and pads (where deck is raised) — concrete pad foundations or Postcrete-set timber posts at 1.8–2.4 m centres. Posts must be Class 4 treated softwood (ground contact rating) — typically 100 × 100 mm or 75 × 75 mm. Concrete: 600 × 600 × 600 mm hole filled with Postcrete or wet mix. £45–£80 per post including labour. For a 25 m² raised deck expect 6–10 posts.

Ground screws (alternative to concrete) — galvanised steel screws driven mechanically. Faster than concrete (no curing wait), no spoil to remove, suitable for many soil types but problematic in heavy clay or stony ground. £35–£65 per screw supplied plus £15–£25 fitting per screw.

Bearers and joists — Class 4 treated softwood. Bearers 100 × 50 mm or 150 × 50 mm sit on posts, joists run between bearers. Joists at 400 mm centres maximum (most common), 350 mm centres for hardwood (which is heavier and benefits from more support). 4×2 (95 × 45 mm) is the typical joist; 6×2 (145 × 45 mm) for spans over 1.8 m.

Joist hangers, post brackets, fixings — galvanised or stainless steel. £4–£8 per hanger; £8–£14 per post bracket. Always specify A4 stainless near coastal sites or in chlorinated splash zones (around hot tubs, swimming pools).

For a 25 m² deck, sub-frame timber alone is typically 100–140 linear metres of joist plus bearers and posts — £350–£700 supplied. Adding fixings, brackets, membrane, stone base and posts reaches £900–£1,600 in materials before the deck boards arrive.

Balustrades and Building Regulations Part K

Approved Document K (Protection from falling, collision and impact) sets the trigger for balustrade requirement. The threshold is a fall of more than 600 mm — measured from the finished deck surface to adjacent ground.

Where the trigger applies:

For pricing:

Where the deck is below 600 mm to ground, balustrade is not required by Part K but is often specified for safety where children, dogs or pool/pond access make a fall consequential. A single handrail at 900 mm without spindle infill is the lowest-cost option — £35–£55 per linear m fitted.

Steps, Risers and Access

Almost every raised deck includes at least one step. For pricing:

Step construction — typically two stringers (notched 9×2 timber) with risers and treads. Tread depth 280–320 mm, riser height 150–190 mm comfortable. Maximum riser 220 mm under Part K.

Per step fitted — £85–£180 each for timber, £120–£260 for composite-matched, £180–£380 for hardwood.

Wider stairs (full-width "garden steps" 1.8–2.4 m wide) — £450–£900 per flight of 3–4 steps fitted.

Ramped access — where wheelchair or mobility access is required, ramp gradient maximum 1:12 under Part M. Substantially more material and more costly than steps; £180–£280 per linear m of ramp run.

Whole-Life Cost: Composite Versus Softwood

The 20-year economic comparison favours composite once maintenance is monetised:

Softwood deck, 25 m² at £75/m² fitted = £1,875

Composite deck, 25 m² at £180/m² fitted = £4,500

The composite premium is recovered around year 7–10 in most scenarios. Quotes that show this whole-life calc convert better than ones that quote only the upfront figure.

Programme: A Typical 25 m² Composite Deck

Day 1: Mark out, dig post holes, set posts in Postcrete (cure overnight) Day 2: Lay membrane, stone base where needed, install bearers and joists Day 3: Fit deck boards (composite hidden-fix system slows pace vs softwood) Day 4: Fascia, trims, steps, balustrade fitting Day 5: Final clean, snag-list, customer hand-over

Add 1–2 days where ground prep is heavy (clay, slope), where balustrade is steel/glass (specialist install), or where the deck wraps around a building.

Cost to Build a Garden Deck — Consumer Quick View

For a homeowner asking "how much does decking cost in the UK in 2026":

These ranges include sub-frame, ground prep, materials, fittings and labour. Add VAT at 20% if quoted ex-VAT (most domestic deck contractors quote VAT-inclusive). Add £350–£900 if planning permission is needed (raised decks above 300 mm in some locations, or close to boundaries — see when decking needs planning permission).

Frequently Asked Questions

Do I need planning permission to install a deck?

Most ground-level domestic decks are permitted development. Planning permission is needed where the deck is higher than 300 mm above natural ground and either covers more than 50% of the garden or is in front of the principal elevation. Conservation Areas and Listed Buildings have stricter rules. Always check with the local authority or see the decking planning permission rules.

How long does composite decking last compared to softwood?

Modern capped composite carries 25-year residential warranties from major manufacturers. Treated softwood has a 15–20 year design life if maintained; without maintenance, board replacement starts at year 7–10 in heavily-trafficked areas. The composite premium pays back in 7–10 years on whole-life cost.

Can I install a deck on a slope?

Yes — raised decks on stepped post heights are the standard solution for sloping gardens. Each row of posts is set to a different cut length to bring the deck to level. A 25 m² deck on a 1:12 slope adds 1–2 days to the programme and 8–12% to materials cost (more posts, longer joists, more bracing).

What's the cost difference between iroko and balau hardwood?

Iroko is typically £75–£110 per m² supplied; balau is £55–£85 per m² supplied. Iroko is denser, more dimensionally stable, and the standard for high-end UK decks. Balau is good value for the dense hardwood look at sub-iroko price but can be more variable in quality between consignments.

Should I use ground screws or concrete posts?

Ground screws save 1–2 days on the programme (no curing wait) and produce no spoil. They cost roughly 50% more than concrete posts in materials but save labour. Concrete is more forgiving on rocky or variable ground. For most level UK gardens, concrete remains the default; for fast turnarounds or ground-water-sensitive sites (near drains, near tree roots), ground screws win.

Regulations & Standards