Do You Need Planning Permission for a Deck or Pergola?

Most decks and pergolas in England do not need planning permission. They fall under permitted development, which means you can build without applying, provided you stay within limits.

The trouble is that the limits are specific, and people find out they have crossed one after the deck is built. Here is what actually decides it.

A caveat worth reading: the rules below apply to houses in England, and they are the general position. Flats and maisonettes are excluded from permitted development altogether. Listed buildings, conservation areas, National Parks and Areas of Outstanding Natural Beauty all carry extra restrictions. Some properties have had permitted development rights removed by a planning condition — new-build estates do this more often than people expect. Always confirm with your local planning authority before you build.

Decking: the 300mm rule

The number to remember is 300mm.

Decking is normally permitted development if the finished platform sits no more than 300mm above the ground, and if, together with other extensions and outbuildings, it covers no more than 50% of the land around the original house.

Go above 300mm and you are usually into planning permission territory. That catches more people than any other rule, because gardens slope. A deck that is flush with the back door can easily be well over 300mm at the far end of a sloping lawn.

“Original house” means the house as first built, or as it stood in 1948. Previous owners’ extensions count against your 50%, not just yours.

Pergolas and garden structures

A pergola is generally treated as an outbuilding. The usual limits: no more than 2.5m high if it sits within 2m of a boundary; otherwise up to 3m for a flat or mono-pitched roof, or 4m for a dual-pitched roof; not forward of the principal elevation, which in plain terms means not in the front garden facing the road; and together with other outbuildings, no more than 50% of the land around the original house.

Most pergolas over a patio sit comfortably inside these. The 2.5m boundary limit is the one to check, because a pergola tall enough to walk under comfortably with a pitched top can exceed it if it goes near a fence.

Overlooking and privacy

Even where the rules are met, a raised deck that looks directly into a neighbour’s garden or windows is the most common source of complaints and disputes.

Permitted development does not require you to consult neighbours. We would still suggest you talk to them for anything raised. A conversation before the build costs nothing. A retrospective planning application, or a neighbour dispute you have to declare when you sell the house, costs a great deal.

Building regulations are separate

Planning permission and building regulations are different things, and meeting one does not mean meeting the other.

Decking generally does not need building regulations approval. It can, if it is raised enough that a fall becomes a safety issue, or if it forms part of a means of escape, or if it attaches to the house in a way that affects the structure. Raised decks need suitable balustrades regardless of what the regulations require of you — the standard for a domestic guarding height exists for good reason.

Other things that catch people out

Party walls. Building close to or against a shared boundary structure may bring the Party Wall Act into play.

Covenants. Your deeds may restrict what you can build regardless of what planning allows. This is common on newer estates and completely independent of the council.

Trees. A tree with a preservation order, or any tree in a conservation area, cannot simply be removed or cut back to make room.

Drainage. You cannot build over an inspection chamber without agreement from the water authority.

The short version

Ground-level decking and a modest pergola over a patio: almost certainly fine.

Raised decking, anything tall near a boundary, anything in a front garden, or any work at a listed building or in a conservation area: check first.

If you are not sure, your local planning authority — Guildford Borough Council, Woking Borough Council, Waverley Borough Council and the rest — will give you an answer, and a formal Lawful Development Certificate if you want it in writing.

We can help you work it out

We design around these limits every week, and we will tell you at the site visit whether what you want is likely to need permission. We will not tell you it is fine when it is not — an unlawful deck becomes your problem when you sell.

See our decking and pergola pages, or book a free site visit.