Composite or Timber Decking? Priced Side by Side

The Short Answer

By Gary Hodson · Ex-Army. I do the sums so you buy the right amount. · Prices read off the Wickes and B&Q pages on 8 October 2026; spacing and warranty figures checked against the sources below · Last reviewed 8 October 2026

Composite costs about twice as much as treated softwood to put down, and it asks for much less of your time. For a 3m x 3.6m deck, our sum comes to about £605 for Wickes Pro softwood and about £1,340 for Trex Enhance composite, counting only the boards, the joists and the fixings. That is roughly £56 and £124 a square metre, in materials only.

Choose timber if the money is tight or you may move within a few years. Choose composite if you want to stop oiling and expect to own the deck for 15 years or more. Neither material is slip-proof, and neither is cool in July if you pick a dark colour.

This page is about which material to buy. For the quantities your own deck needs, use the decking calculator.

What the Boards Cost Per Square Metre

All prices were read on 8 October 2026 and are shown to shoppers without delivery. Wickes rounds to whole pounds. The per square metre column is the price divided by the cover each retailer states, except the B&Q board, where we multiplied length by width ourselves. It is the face area only, so it ignores board gaps and offcuts. The worked sum below adds both.

Lifespan: A Guarantee Is Not a Lifespan

The Timber Decking and Cladding Association (TDCA) treats 15 years as the minimum standard for a quality timber installation, and says 30 and 60 years are achievable with the right timber and detailing.⁶ Travis Perkins sells a pressure-treated pine board it describes as giving a 15 year service life.⁷ At the cheap end, Wickes guarantees its Standard board for 5 years against rot and its Pro board for 10.¹²

Trex gives its Enhance composite a 25 year limited warranty for homes. It covers fungal decay and splitting, and also fading and staining, if the deck is fitted to the instructions. Commercial use gets 10 years.³ That is a long promise. It is still a list of named faults with conditions attached. Trex says a pressure washer above 3,100 psi could damage the boards and void the warranty, and that food spills must be cleaned within seven days to keep the stain warranty.⁹

So the fair comparison is a trade body’s 15 year floor for timber against one maker’s 25 year promise for composite. Neither is a test of how your deck will age in your garden.

Upkeep: Oil Every Year or Wash Twice

Wickes tells buyers of its Pro board to keep it clean and to recoat all sides with a deck seal, oil or stain to help stop the boards splitting or warping, and to guard against rot.² A 2.5 litre tin of Wickes water-based decking stain was £20 on 8 October 2026.⁸ Read the tin for how often and how much, because coverage differs between products.

Composite is not maintenance-free. For the Enhance range, Trex says warm soapy water and a soft brush are enough, and that mould can feed on pollen and dirt left on the surface, so you still have to wash it.⁹ Trex allows a pressure washer up to 3,100 psi on Enhance, with a fan tip no closer than 203mm. Other makers set lower limits, so check yours before you hire one.⁹

The money side is simple. The gap in our worked sum is about £735. Even if you used a whole 2.5 litre tin every year for 15 years, that is 15 tins and £300. On cash alone timber wins. Composite wins on your weekends.

Slipperiness: Neither Material Wins Automatically

The TDCA says dirt, leaf litter and other organic growth, including algae and moss, can lower grip on any outdoor surface, and that damp, shaded decks need cleaning more often.¹⁰ It points to the Pendulum Test, which gives a value called the PTV. A wet PTV of 36 or more is the usual mark for low slip risk. 25 to 35 is moderate, and 24 or below is high.¹⁰

Grooves do not fix this. The TDCA code says you should not assume grooved or ribbed boards improve slip resistance, and that only boards with anti-slip strips set into them do.⁶ We found no neutral pendulum test comparing timber and composite side by side, so we will not rank them. Ask the seller for the wet PTV of the exact board.

Heat: Colour Matters More Than Material

Ultra Decking, which sells decking, reports surface temperatures of 48 to 69°C for softwood and 56 to 65°C for capped composite. It adds that dark timber and dark composite land at nearly the same temperature, over 60°C.¹¹ EnviroBuild, which sells composite, says composite often stays cooler than darker-stained timber because of its lower thermal conductivity.¹²

Both are sellers’ own claims, and they point in different directions. The part they agree on is colour. On a south-facing deck, choose a lighter shade, and think twice about dark boards if you walk on it barefoot.

Joist Spacing: Composite Needs a Tighter Frame

The softwood rows come from Table 5 of the TDCA code, which lists maximum board support centres. It has no row for a 25mm board, so check the label before you assume 400mm with a budget 25mm board.⁶ EnviroBuild says diagonal composite layouts need 250 to 300mm centres, and that most composite profiles need centres no wider than 300mm.¹³ The joist counts are our arithmetic: span divided by centres, plus one.

This agrees with the decking calculator, which offers 400mm centres for softwood and 300mm for composite.

Fixings: Screws for Timber, Clips for Composite

For timber, the TDCA code asks for screws at least 2.5 times the board thickness, so about 68mm for a 27mm board, with two at each joist crossing. It sets grade 316 stainless steel as the minimum, and also accepts silicone bronze, hot-dip galvanised fixings and high performance coated steel. Electroplated and brass fixings, and plain steel ones, must not be used outdoors.⁶ The code is written for raised decks on new homes. It also says nails and clips are not appropriate where a 30 or 60 year life is wanted.⁶

Composite usually goes down on hidden clips. A box of 90 Trex Hideaway clips with screws was £40 on 8 October 2026, and Wickes says one box covers 4.5 m².¹⁵ Starter clips (a bag of 36, £38) and colour-match screws for the last board (a box of 75, £24) are extra.¹⁶ Do not mix brands. Dino says only its own fasteners work with its boards.¹⁴ The Trex Enhance Basics board we priced is square-edge, and Trex tells you to route square-edge boards on the underside, along the full length or at each joist crossing, to take Hideaway clips.¹⁹ The £222 fixings budget does not include a router and bit or grooved boards, so allow for that if you choose this board.

Worked Sum: a 3m x 3.6m Deck

This is GardenCalc’s own sum: 10.8 m², boards running across the 3m width, 10 per cent wastage and a 5mm gap between neighbouring boards. Our decking calculator may round the row count differently, so expect small differences. The composite gap is within the 3 to 6mm range EnviroBuild gives.¹³ It prices boards, joists and fixings only.

How we got the numbers that need explaining:

• Joists. Wickes sold a 45 x 95mm C16 treated joist at £10 for a 3.6m length. We sized the deck at 3.6m so each joist is one whole length and no splice is needed. The same price is used for both columns. A joist run longer than 3.6m needs a longer length or a joint, so price that separately.¹⁷ That Wickes page says the timber is not suitable for direct ground contact. If your joists will touch the ground or sub-base, you need a ground-contact class and the price rises.
• Screws. 24 rows x 9 joists x 2 screws = 432, plus 10 per cent = 476. We used the Wickes 4 x 75mm pack of 200 at £9.50 because 75mm clears the TDCA length rule. Check the finish is one the code accepts.¹⁶
• Last row. 24 full composite boards cover 3,475mm of the 3.6m, which would leave 105mm bare once the 10mm edge clearances are allowed for. The 25th row is a board ripped to about 100mm. Timber needs no rip: its 24 rows cover 3,571mm.
• Clips. 25 rows x 11 joists is 275 crossings. Minus 11 starter positions, plus 10 per cent, gives 291 clips, so 4 boxes of 90. Wickes’ own 4.5 m² per box suggests 3, so our count is the cautious one.
• Offcuts. A 3m width cut from 3.6m or 3.66m boards leaves a 600 to 660mm offcut per board. You can reuse some for borders, so the 10 per cent wastage may be generous.
• Cheaper timber. Wickes Standard 25 x 120 x 3600mm boards were £11²⁰. At 5mm gaps, 28 full rows cover 3,495mm, so a 29th row is ripped to about 80mm (28 x 120 + 80 + 28 x 5 = 3,580mm). That is 29 x 1.1 = 31.9, so 32 boards with wastage, and £352 for boards. Confirm the joist spacing for a 25mm board first.

Left out of both columns: delivery and labour, posts or pads, weed membrane and any sub-base. Those are the same either way. The sub-base calculator covers the stone, and the concrete calculator covers post holes if you raise the deck.

Common Mistakes

• Using timber-deck joist centres for composite. If the sheet says 300mm and you build at 400mm, the boards can sag. That is the cheapest mistake to avoid and the dearest to fix.
• Buying joists that are not rated for the ground. Read the class on the label, not just the word “treated”.
• Skipping expansion gaps. The TDCA asks for 5 to 8mm between timber boards.⁶ EnviroBuild asks for at least 3 to 6mm between composite boards, 8mm at board ends, and 20mm at walls and joist butt joints.¹³ Your maker may differ.
• Forgetting ventilation. EnviroBuild asks for at least 50mm under composite over a hard surface and 300mm over soil, with a fall of about 1 in 80.¹³
• Mixing fixings across brands. The clip is part of the board system.¹⁴
• Trusting grooves for grip. Only anti-slip strips count, according to the TDCA.⁶
• Raising the deck without checking the rules. In England, decking over 30cm above the ground needs planning permission.¹⁸

Which One to Buy

• Treated softwood suits a tight budget, a short stay in the house, or a deck you are happy to oil. Pick a 27mm or thicker board, a ground-rated frame and proper screws.
• Composite suits a long stay and a dislike of upkeep. Budget for 11 joists, not 9, and for the maker’s own clips.
• Still undecided? Ask for a sample of each, leave both outside through a wet month, and look at them in the sun. A shade that looks right in the shop can run hot in July.

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