How long does composite decking last, and is it worth it?

"How long does composite decking last?" is usually the question behind "is it worth the extra?" and the honest answer has two parts: how long the boards last, and how long whatever they are sitting on lasts. The boards are the easy half. This guide gives real lifespans for composite boards, for the three kinds of frame that go under them, and for timber by comparison, then works out whether composite pays for itself.

The short answer

Composite decking boards last 25 to 30 years in a British garden, and often longer. Ours carry a ten-year warranty and will outlive it. What decides the life of the deck is the subframe: a treated softwood frame on damp soil goes in 8 to 15 years, a composite batten frame on a patio or a recycled plastic joist frame on posts lasts as long as the boards. Build the frame from rot-proof material and a composite deck is a 25-year purchase for about £800 in materials on a 3.6m by 3m deck. Against timber, it is cheaper to own from about year five.

How long the boards last

Composite is roughly half wood fibre and half plastic, bonded under heat. Nothing in it rots, nothing in it feeds insects, and it does not split or splinter. What ages it is ultraviolet light and abrasion, and both act slowly: a slight lightening of colour in the first summer, then a stable surface for decades. Hollow boards like ours are lighter than solid ones and equally long-lived provided the cut ends are capped so water and frost stay out of the core. Manufacturers' warranties run from 10 to 25 years; the boards themselves generally outlast the warranty by a margin.

What shortens the life of a board: face-screwing instead of clipping, so it cannot expand and buckles; joists too far apart, so it flexes and creaks; open ends that let water into the core; and pressure-washing at close range, which lifts the surface. All four are avoidable and all four are in the installation guide.

How long the frame lasts

Frame	Typical life	Notes
Treated softwood on damp ground	8 to 12 years	The commonest failure: boards still perfect, joists rotten underneath
Treated softwood, off the ground on pads, joist tape, 40mm airflow	12 to 15 years	Acceptable if built carefully
Composite battens on a patio or concrete	25 years plus	Cannot rot; the right frame for a ground-level deck
Recycled plastic joists and posts	25 years plus	About twice the price of timber; never needs replacing

When a timber frame fails, the boards come up to replace it, so the cost of the "cheap" frame arrives at year ten with labour attached. The subframe guide compares the three options with prices.

Composite against timber, year by year

A timber deck board lasts 10 to 15 years if it is cleaned and re-oiled every year or two, and 5 to 8 if it is not. Over the same 25 years a composite deck needs a wash in spring and autumn. In money, on a 3.6m by 3m deck: timber boards cost about £250 less to buy, then £60 in oil or stain plus a weekend every other year, then a full replacement around year twelve. Composite boards cost £500, need nothing, and are still there at year 25. The break-even is around year five; from then on composite is the cheaper deck to own. The composite versus timber guide lays the ten-year figures out side by side.

What does not change with age

• Grip. The textured faces do not wear smooth. A ten-year-old composite deck grips as well as a new one once it is washed.
• Strength. Boards do not soften or sag over time when supported at 350mm centres.
• Colour after year one. The first-summer settling is the only visible change; after that the colour holds. The fade guide explains it.

What does change

• Surface scratches accumulate from dragged furniture and grit, and blend in with weathering.
• Algae in shade returns each winter and comes off each spring; see how to clean composite decking.
• Clips can loosen if the frame moves; a tightening every few years is the only maintenance the fixings need.

Is it worth it?

For a deck you expect to keep more than five years, yes, on cost alone, before counting the weekends not spent oiling. For a deck in a rental you will re-do in three years, or a temporary platform, timber is cheaper on day one and that is what matters there. The exception that surprises people is the frame: spending an extra £100 to £300 on battens or plastic joists is what turns a ten-year deck into a 25-year one, and it is worth more than any upgrade to the boards.

The cost guide prices three decks in full, frame included, and free samples let you see the board that will still be there in 2050.

Frequently asked questions

How long does composite decking last in the UK?

The boards last 25 to 30 years in a British garden and often longer; ours carry a ten-year warranty and outlive it. The frame decides the life of the deck: treated softwood on damp soil goes in 8 to 15 years, composite battens or recycled plastic joists last as long as the boards.

Does composite decking rot?

No. The wood fibre is bound in plastic, so it does not rot, split or splinter, and nothing eats it. Water sits on the surface and dries off; the only wet-weather problem is algae on a shaded deck, which brushes off.

Is composite decking worth the money over timber?

For a deck you keep more than five years, yes. Composite costs more on day one and nothing after that; timber needs cleaning, oiling or staining every year and replacement boards from about year seven. Composite is cheaper to own from about year five.

What is the warranty on composite decking?

Ten years on our boards, and the realistic life is 25 years or more. A frame of composite battens or recycled plastic joists lasts as long as the boards; a timber frame does not.

Boards, trims and frame parts are priced on the composite decking price list; free samples in every colour.