Do I need planning permission for decking?

The rules for a house

Garden decking at a house in England falls under permitted development, so no planning application is needed, provided it meets every one of these conditions.

• The decking is no more than 30cm above the ground.
• Together with any extensions, outbuildings and other platforms, it covers no more than half of the garden area.
• No part of it is on land in front of the wall forming the principal elevation, which is normally the front of the house.

There are tighter limits on designated land. In conservation areas, National Parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites, no decking is permitted at the side of the house. In National Parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites, decking more than 20 metres from the house is also limited to 10 square metres. Within the curtilage of a listed building, no decking is permitted development at all.

Wales has its own permitted development rules, and Scotland and Northern Ireland separate systems, so check with the council there.

Flats and maisonettes

Permitted development for decking applies to houses only. Flats, maisonettes, houses converted into flats, and homes created through certain other permitted development rights do not have it, so decking at a flat needs planning permission. A leasehold flat will usually need the freeholder's consent as well.

Raised decking and the 30cm rule

Anything over 30cm needs a householder planning application. Councils look closely at raised decks because of overlooking: a platform a metre up gives a clear view into neighbours' gardens and windows that a ground-level deck does not. Screening, setting the deck back from the boundary and keeping it low all help an application.

On a sloping garden, a deck that is level with the top of the slope can be well over 30cm at the bottom. If the height is close, ask the council how they will measure it before building, not after. Height also means more structure: posts, bracing, steps and guarding, all of which add cost.

Building regulations

Planning permission and building regulations are separate. Most low garden decking needs no building regulations approval. The Planning Portal's guidance is that building regulations should be assumed to apply to every deck structure that needs planning permission, so a raised deck needing an application should be discussed with building control too.

For guarding, carpenters and building control work to Approved Document K. In a house it asks for guarding wherever there is a drop of more than 600mm, 1100mm high on external balconies, and with gaps too small for a 100mm sphere to pass through. A raised deck off a back door is close enough to a balcony that building to those figures is the sensible standard.

How to be sure before you build

If you want certainty, apply for a Lawful Development Certificate. It is a formal confirmation from the council that the decking does not need planning permission, and it is useful when you sell. Check the property's title too. Covenants on newer estates sometimes restrict structures in gardens regardless of planning law, and some estates have had permitted development rights removed by a planning condition or an Article 4 direction.

If decking has already gone up above 30cm without permission, the usual route is a retrospective application. The council can take enforcement action if it is refused, which can mean lowering or removing the deck.

Why so many decks end up over 30cm

The usual reason is the back door. A deck feels right when it is level with the threshold, but many houses have a floor well above the garden, so a deck at door height can be 40cm or 50cm up at the far end before anyone has thought about planning. There are simple ways round it: a step down from the door onto the deck, a deck split into two levels that follows the ground, or digging the garden down slightly where the deck sits. Each keeps the platform low, and a low deck is also cheaper to build and easier to keep ventilated.

Other things that catch people out

A deck against the house must sit at least 150mm below the damp proof course and must not cover airbricks, whatever its height. Decking right up to a boundary is allowed within the rules above, but a raised deck by a fence is worth talking over with the neighbour first, and fixing the frame to a neighbour's fence needs their agreement. Check where water will drain, especially on clay, and keep the area under the deck ventilated so the frame lasts.

Getting a raised deck built

Ask the carpenter to confirm the finished height at its highest point, whether they think planning permission is needed, and how the guarding will be built. Decking typically costs £60 to £110 per square metre supplied and fitted; steps add around £150 to £400 a flight and balustrade £60 to £120 a metre. A raised deck costs noticeably more than a ground-level one of the same size because of the posts and bracing underneath.