Larch and composite decking end up on the same shortlist for good reason. Both are far more durable than a cheap softwood board, both come in long lengths you can lay in a weekend, and neither asks for the annual sanding-and-staining marathon a pine deck demands. The split comes down to money, feel underfoot, and how honest you are about the upkeep you will actually do.
Here is how they compare on the things that decide it in a British garden.
What you pay up front
Larch sits in the middle of the market. It costs noticeably more than basic pine or spruce, because the heartwood resists rot far better, and noticeably less than most hardwoods. Composite usually costs more again per square metre, sometimes a lot more, depending on the brand and whether the boards are capped with a polymer skin.
The boards are only part of the bill, though. Budget for the whole assembly:
- Substructure. Joists, posts and bearers, plus a weed membrane and, on a raised deck, proper ventilation underneath.
- Fixings. Larch wants stainless steel or hot-dip galvanised screws. Composite usually needs proprietary clips and starter boards, which are not cheap.
- Waste. Order 10 per cent extra, more if the deck has angles, steps or a diagonal layout.
- Labour. Composite can be slower to fit because of the clipping system and the expansion gaps. Larch is quicker to screw down.
Some composite systems also specify their own joists rather than timber. That pushes the price up further, so ask what the warranty requires before you assume you can use treated timber.
Appearance: grain, colour and how each ages
Fresh larch is a warm pale gold with reddish tones, a visible grain and the odd knot. Left bare, it weathers to a soft silver grey within a couple of seasons, which suits cottage gardens and coastal planting. Oiled every year or two, it keeps a deeper honey colour. Boards vary between packs, so open three or four and mix them as you lay, otherwise you get a patchwork of light and dark runs.
Composite is uniform. No knots, no sapwood, no grain running out at the ends, and a colour range that now includes convincing greys and weathered browns. Some boards look like timber from two metres away; others look like plastic up close, so get a sample and view it wet, dry and in shade rather than under showroom lights. Capped boards hold their colour well; uncapped ones can chalk and fade.
Grip when it is wet
Both get slippery, and neither is magic. The real enemy is a film of algae, which builds fastest on a north-facing deck under trees or beside a pond.
Choose a grooved or ribbed larch profile rather than a smooth one, and brush it down a few times a year. On composite, pick a brushed or textured surface; smooth capped boards in deep shade are the worst offenders, particularly when new and still carrying mould-release residue. Bear in mind that dark composite gets genuinely hot in full summer sun, which matters if children use the deck barefoot.
Maintenance: two very different jobs
Larch is a natural material that wants attention, but the routine is simple:
- Sweep leaves and debris off, especially in autumn, so damp litter does not sit on the surface.
- Wash once or twice a year with a stiff brush and a suitable deck cleaner.
- Re-oil every one to three years if you want to keep the colour. Larch is dense and absorbs oil slowly, so apply thin coats and expect it to look patchy at first.
- Sand back any raised grain or splinters, usually on the edges that see foot traffic.
Composite asks for soap, water and a brush. No sanding, no staining, no sealing. That said, greasy marks from a barbecue, red wine or a dropped sausage can be stubborn on a textured surface, and scratches from pet claws or dragged furniture tend to stay. Mildew can still grow on it in a damp, shaded spot. Low maintenance does not mean no maintenance.
Lifespan and UK weather
A properly laid, well-ventilated larch deck commonly gives a couple of decades or more. Most of the failures come from bad detailing rather than bad boards: joists set too far apart, boards butted tight with no drainage gap, timber buried in soil or gravel, or end grain left unprotected. Keep joists at sensible centres, leave a gap of around five to eight millimetres between boards, keep timber clear of the ground and let air move underneath.
Also check what you are buying. Larch heartwood is durable; the pale sapwood is not. Cheaper boards often include a sapwood edge that greys and softens first, so ask about the grade.
Composite handles wet winters and freeze-thaw cycles without rotting, and warranties commonly run well into double figures of years. Read what they cover, since labour is often excluded and fading may be capped. Composite expands and contracts more than timber with temperature, so it needs expansion gaps and should not be jammed tight against a wall. Fit it short and it can buckle in a hot spell; fit it with room to move and it behaves.
Which one should you choose?
Pick larch if you want real timber underfoot, do not mind an annual clean and a coat of oil, and would rather spend less now. It scratches and dents more easily than composite, but you can sand out marks and replace a single board without hunting for a matching batch.
Pick composite if low upkeep is the priority, the deck sits in shade or under trees, or you want a colour that stays put. Buy two or three spare boards at the same time and store them, because matching a colour or profile a few years later is difficult.
Whichever you choose, sort out the substructure first. That is what determines how the deck performs in a wet British winter, and it is the part nobody sees. If your deck will be raised, close to a boundary or more than a modest height above the ground, check the planning position with your local authority before you order anything.
Photo: susannp4 / Pixabay
