Choosing Decking: Timber, Hardwood or Composite

Pressure-treated softwood, usually pine or spruce, is the cheapest option by a wide margin and is what most existing decks are built from. Treated to the correct use class for ground contact or above-ground use, it performs reasonably.

Its weaknesses are movement and surface. Softwood absorbs and releases moisture, so boards cup, twist and split over time, and gaps open and close seasonally. It also weathers to a silver-grey unless treated, and it hosts algae readily in shade.

The grooved boards so common in Britain are the main reason decking has a reputation for being slippery. The grooves trap dirt and moisture and do nothing for grip when wet — reeded or smooth boards laid with the smooth face up actually perform better, and anti-slip inserts or a grit-based coating are effective where needed.

Softwood needs cleaning annually and treating with a decking oil or stain every one to two years. Neglected, a softwood deck reaches the end of its usable life in eight to twelve years.

Hardwoods such as balau, ipe, iroko and European oak are dense, naturally durable and dimensionally far more stable than softwood. A well-built hardwood deck lasts twenty-five years or more and can look superb.

The material cost is high and it is harder to work — every fixing needs pre-drilling, blades blunt quickly, and the density makes boards heavy to handle. Labour costs are correspondingly higher.

Hardwoods weather to silver-grey unless oiled, which some people prefer. Oiling annually maintains the original colour and takes real effort on a large deck.

Source matters. Insist on FSC or PEFC certified timber. Some tropical hardwood decking is associated with poorly managed forestry, and certification is the only practical assurance.

Composite boards combine wood fibre with recycled polymer. They do not rot, do not splinter, do not need oiling and hold their colour. For most domestic gardens they are now the default recommendation, and they are what we install most.

Capped composite, with a co-extruded polymer skin, resists staining and fading much better than uncapped board and is worth specifying. Solid boards are stiffer than hollow ones and allow slightly wider joist spacing, though most systems specify 300 to 400mm centres regardless.

The advantages are real: no annual treatment, excellent slip resistance in most quality ranges, no splinters underfoot, and a twenty-plus year warranty on good systems. Maintenance is washing.

The trade-offs are cost — typically double good softwood — expansion and contraction with temperature that demands correct gapping at board ends, and heat retention, as dark composite gets genuinely hot in direct summer sun.

It is also less repairable and less adaptable. A damaged board is a proprietary component, and modifying a composite deck later is harder than with timber.

Whatever the boards, the frame beneath is what determines how long the deck lasts and how it feels underfoot. Almost every bouncy, sagging deck we are called to has an undersized or badly supported frame.

Joists should be sized for the span and set at the spacing the board manufacturer specifies — typically 400mm centres for timber and 300 to 400mm for composite, closing to 300mm or less where boards run diagonally.

Bearers must sit on solid, load-bearing supports: concrete pads or piers on undisturbed ground, not paving slabs dropped on topsoil. The whole frame should be level, braced and fixed with galvanised or stainless fixings — near the Essex coast, salt air destroys ordinary steel.

Ventilation beneath is essential. Air needs to move under the deck to keep the frame dry, which means a clear gap to the ground and open or vented fascia rather than a sealed box. A deck enclosed tightly to the ground rots from underneath regardless of the board material.

A weed membrane and gravel beneath prevents growth pushing up through the boards and keeps the ground beneath drier.

A deck at ground level in a rear garden is generally permitted development. A raised deck with a platform more than 300mm above ground may need planning permission, and raised platforms bring overlooking considerations that planners take seriously.

Any deck more than 600mm above ground generally needs a balustrade, and the balustrade must be structurally adequate rather than decorative. Balustrade infill should not create a climbable ladder effect where children use the garden — vertical balusters rather than horizontal rails.

The deck surface must sit at least 150mm below the damp-proof course of the house, and it must not block airbricks. Where a doorway is low, a stepped-down deck with a drainage gap at the wall is the correct detail.

Steps down from a deck need consistent risers and generous treads, and lighting at step edges is a genuine safety measure on a surface used after dark.

Choose softwood where budget is the deciding factor, the deck is small, and you are content to clean and treat it annually.

Choose hardwood where appearance is paramount, the property warrants it, and the maintenance is either acceptable or the silver-grey weathered look is wanted.

Choose composite for most family gardens, for anywhere maintenance access is difficult, for shaded and damp positions where timber struggles, and where the deck needs to look consistent for twenty years without attention.

Whichever you choose, spend on the substructure. It is the part that cannot be upgraded later, and it is the difference between a deck that feels solid in year fifteen and one that needs rebuilding in year eight.