Composite versus timber decking after five British winters

Anyone can quote you the marketing on composite decking. What is harder to find is someone who built both, in this climate, and went back five years later to look.

We have. Here is what we found, including the bit the composite manufacturers do not lead with.

What actually happened to both

The softwood decks — pressure-treated pine, the standard British deck — were mostly still structurally sound at five years, and mostly looked tired. Colour had gone silver-grey wherever the owner had stopped re-staining, which was most of them by year three. Boards had cupped slightly. Shaded, north-facing sections were green with algae by every autumn and needed a wash and a stiff brush to be safe underfoot.

The hardwood decks were a different story — still handsome, still dense, still worth the money, and roughly double the cost of softwood at installation.

The composite decks looked broadly like they did on handover. Some slight fading in full sun on the darker boards, which is normal and stated in the warranties. No cupping, no splinters, no algae worth mentioning. What they did have, in a couple of cases, was staining around a barbecue where hot fat had gone down. Composite is not fireproof and it is not entirely stain-proof.

Nobody has ever rung us to complain that their composite deck looks old. Several people have rung to say they have stopped staining the timber one and could we quote to replace it. Martin, MAE Landscapes

The frame is the part that fails

This is the important bit and it applies to both materials equally.

In almost every failed deck we have been called to look at, the boards were fine and the frame had gone. Untreated or inadequately treated joists sat too close to wet ground, no ventilation underneath, no gap for airflow, and rot did the rest. Putting twenty-five-year composite boards on a frame that will not last ten is a waste of money, and it happens constantly because the frame is invisible on the quote.

How we build one: joists at 400mm centres for standard composite, closer where the manufacturer requires it or where the deck spans awkwardly. The frame is either treated timber to a use-class suitable for ground contact or, increasingly, aluminium sub-frame where the ground is persistently wet. There is a clear ventilation gap underneath and the deck is never sealed tight to the ground at every edge. Joist tape over the top face of every joist stops water sitting on the timber where the fixings penetrate — a cheap detail that adds years.

What composite is and is not

Composite decking is wood flour mixed with recycled polymer, extruded into boards. The boards worth buying are capped — a hard polymer shell bonded around the core on all four sides. Uncapped composite, which is what the cheapest boards are, absorbs water at the edges, stains, and fades badly. If you take one thing from this article: buy capped, or buy timber.

What it genuinely delivers: no staining or sealing, no splinters, no rot, very good colour retention, and a surface that is easy to keep clean. Warranties on the better systems run to twenty-five years on residential installations.

What it does not: it is not indestructible. It gets hot in direct summer sun — noticeably hotter than timber, which matters if children are barefoot on it. It scratches if you drag metal furniture across it. It marks from hot fat and from certain leaf tannins if left. And it is not a structural material — it goes on a frame, always.

When timber is still the right answer

We are not against timber and we still build timber decks. It is the right call in three situations.

Budget. Softwood is meaningfully cheaper up front. If the choice is a well-built softwood deck now or no deck at all, build the softwood deck properly.

Character. On a period property, or in a woodland-feel garden, hardwood has a depth and grain that composite does not replicate. Composite has become very good; it has not become oak.

You actually enjoy the maintenance. Some people genuinely like the annual ritual of cleaning and oiling a deck, and a maintained hardwood deck at ten years is a beautiful thing. If that is you, buy hardwood and enjoy it.

Ten-year cost, both materials

A 25 square metre deck, built on the same frame specification, real numbers from our jobs.

Softwood and composite land in roughly the same place over a decade — except the composite still has fifteen years left in it and looks like new, and the softwood is due for replacement.

How we build a deck

The verdict

For most gardens in this part of the world — wet, shaded in places, and owned by people who do not want to spend a weekend every spring sanding — capped composite on a properly ventilated frame is the right answer. It costs about the same as softwood over ten years and it will still be there, looking much as it does now, at twenty-five.

Buy hardwood if you love timber and will maintain it. Buy softwood if the budget says so, but spend the money you save on the frame rather than the boards.

Do not buy uncapped composite. It is the worst of both.

Heat, grip and barefoot use

Two practical differences that rarely appear in the marketing.

Composite gets hot. In direct summer sun, a dark composite board will be noticeably hotter underfoot than timber — the dense polymer absorbs and holds heat. On the handful of genuinely hot days we get, a dark deck in full sun can be uncomfortable barefoot. If the deck is south facing and children will be on it, go for a lighter board. It makes a real difference and costs nothing extra.

Grip differs by finish. Wood-grain embossed composite has good grip wet or dry. Some of the smoother, more uniform finishes are slippery when wet and covered in algae, which in a shaded north-facing garden is most of the winter. Grooved boards drain and grip better; smooth boards look cleaner. We would take grip on any deck with steps.

Timber, for its part, gets slippery with algae in shade and needs a wash and a brush each autumn to stay safe. Neither material is inherently non-slip in a British winter without a bit of attention.

Cleaning, and what not to do

Composite needs washing perhaps twice a year — warm water, mild detergent, a soft brush, working along the grain rather than across it. That is genuinely all.

What to avoid: pressure washers held close on a pinpoint nozzle, which will scar the cap layer and void most warranties. Wire brushes. Solvent-based cleaners. And leaving wet leaves piled on the deck all winter, because leaf tannins will stain composite as readily as they stain stone.

For fat and barbecue marks, deal with them quickly with hot soapy water and a soft brush. Left to bake in over a summer they become permanent. A barbecue mat is two pounds well spent.

Timber needs the same wash plus an annual clean-and-oil or clean-and-stain if you want to keep the colour. Skip it and it silvers, which some people rather like — it is a look, not a fault, provided the frame underneath is sound.

Raised decks, planning and privacy

Most low-level decking is permitted development, but there are thresholds worth knowing before you design something.

A raised platform generally needs planning permission once the deck surface is more than 300mm above ground level. Height, overlooking and loss of privacy to neighbours are the issues planners care about, and a high deck along a boundary is exactly the sort of thing that draws an objection. If you are in a conservation area or the property is listed, additional restrictions apply.

Structurally, anything raised needs designing properly — posts on adequate foundations, bracing, and a balustrade where there is a fall. This is not a place to improvise, and it is one of the reasons we build our own frames rather than subcontracting them.

Our practical advice: if you can achieve what you want at low level by adjusting the ground rather than building up, do. It is cheaper, it avoids the planning question entirely, and a deck that sits flush with the garden almost always looks better than one perched above it.

Where the materials come from

A question we get asked more than we used to, and it deserves a straight answer rather than a marketing one.

Composite is typically made with recycled wood flour and recycled polymer — often reclaimed plastic waste — which is a genuine environmental positive at the front end. The honest counterweight is that at the end of its life a composite board is a mixed material and is not straightforward to recycle again. It lasts a long time, which helps, but it does not disappear.

Softwood is renewable and, if it carries FSC or PEFC certification, comes from managed forestry. It is also treated with preservatives to survive outdoors, which affects how it can be disposed of. Its shorter life means you buy it more often.

Hardwood is the one to ask questions about. Certified hardwood from a managed source is a fine, long-lived material. Uncertified tropical hardwood is not, and the price difference usually tells you which you are being offered. We only quote certified stock and we are happy to show the paperwork.

If the environmental question is the deciding one for you, the most defensible answer is usually the one that lasts longest on the smallest footprint — build a smaller deck out of something that will still be there in twenty-five years, rather than a large one you replace twice.

More detail on how we build composite decks, and on why the riser lighting goes in first.