Does decking need planning permission in London?

Decking under 300mm above ground level and covering less than 50% of the garden is permitted development in most areas. Decking over 300mm, decking in conservation areas visible from public spaces, or decking on listed building curtilages requires a householder planning application.

How long does composite decking last?

Quality composite decking (Trex, Millboard, Cedral) carries a 25-year structural warranty. The surface colour fades slightly in the first year then stabilises. Unlike softwood, it needs no staining or sealing — annual washing with a deck brush and warm water is sufficient maintenance.

What is the best decking for a shaded London garden?

Shaded gardens accelerate algae and moss growth on all deck surfaces. Composite decking with an anti-slip embossed surface is the safest choice for permanently shaded areas. Hardwood species (ipe, garapa) are naturally dense and resist algae better than softwood. Apply a commercial algaecide treatment annually regardless of material.

Can I build decking on London Clay without concrete pads?

Screw-pile foundations (Postech, Techni-Metal) are a viable alternative to concrete pads on London Clay — they are installed in minutes with no excavation and no spoil to remove, making them ideal for tight rear access sites. They perform as well as concrete pads on London Clay and are better suited to sites with TPO-protected trees nearby.

What decking boards are best for a period London terrace?

Hardwood species (iroko, ipe, European oak) are most architecturally appropriate for Victorian and Edwardian terraced houses. If the deck is visible from the street or sits within a conservation area, natural timber with a period precedent — York stone paving is often a stronger choice — is likely to be preferred by the local planning authority over composite materials.

Decking Cost London 2025 | Hardwood, Composite & Softwood

How Much Does Decking Cost in London?

Decking in London costs £100–£180/m² for pressure-treated softwood, £150–£280/m² for composite, and £200–£380/m² for hardwood species such as iroko or ipe. Price includes frame, joists, decking boards and fixings but excludes balustrades. Decking over 300mm above ground level requires planning permission. Most London projects take 3–7 days to install.

Softwood, composite and hardwood: cost comparison

Pressure-treated softwood (typically Scandinavian redwood or FSC-certified pine) is the most affordable decking material at £100–£180/m² installed. It requires annual treatment with preservative oil to maintain colour and resist London's wet winters. Composite decking — polymer-and-wood-fibre boards from brands such as Trex, Millboard or Cedral — costs £150–£280/m² and is maintenance-free, though the plastic-heavy visual character suits contemporary gardens better than period properties. Hardwood species — iroko, ipe (Brazilian walnut), garapa and bangkirai — cost £200–£380/m² installed and are the most durable option, lasting 25–40 years without treatment if allowed to silver naturally. Accoya (acetylated softwood) bridges the gap at £170–£260/m² and offers hardwood-level durability with softwood workability. For conservation area gardens in boroughs such as Kensington & Chelsea or Camden, hardwood or high-quality composite is typically specified to satisfy design quality requirements.

Frame construction and London Clay drainage

Decking performance depends entirely on the subframe. In London, the dominant soil is London Clay — a high-plasticity clay with significant seasonal movement (shrink-crack in summer, heave in winter). A concrete pad or screw-pile foundation isolates the deck frame from clay movement; timber ground-contact posts bedded directly in London Clay will rack within 2–3 seasons. The standard specification is 100×100mm treated softwood posts on 300mm concrete pads at 1,800mm centres, with 47×150mm treated C24 joists at 400mm centres for composite or 600mm centres for hardwood. Joist-to-post connections should use galvanised joist hangers, not toe-nailing. Drainage beneath the deck must be maintained — a 75mm gap between the lowest joist and ground level allows air circulation and prevents rot. On sloping sites, step the frame down with the gradient to maintain consistent board-to-ground clearance rather than building up a deep frame at the low end.

Planning permission and Building Regulations

Decking is permitted development (PD) in most London gardens provided it does not exceed 300mm in height above ground level and does not cover more than 50% of the garden area. Decking over 300mm — common on sloping rear gardens in Lewisham, Haringey and hilly outer boroughs — requires a householder planning application. In conservation areas, any decking visible from a public highway or open space may require planning permission regardless of height; check with the local planning authority before committing to design. Balustrades (required by Building Regulations Part K where a fall of 600mm or more exists) are not in themselves a planning trigger, but their design and materials may be subject to conservation area conditions. Rooftop decking on flat-roofed extensions is normally subject to the same 300mm rule as ground-level decking and may additionally trigger planning if it enables overlooking of neighbouring gardens.