Decking: do I need planning permission?

Garden decking planning permission is not usually required where ordinary domestic decking falls within Class E of Part 1. The important threshold is height: a platform more than 0.3 metres high is a raised platform and falls outside Class E.

Height is not the only test. The position of the decking, the Class E coverage limit, protected land and whether the structure is a substantial part of the house rather than ordinary garden decking can all change the answer.

Decking at the rear of a house

The Government’s technical guidance states that decking comes under Class E of Part 1 as an outbuilding. But this needs to be read in context. This and the GPDO states that it may not be higher than 0.3m as otherwise it would be classed as a raised platform. 

The Government’s householder guidance expressly treats ordinary garden decking under Class E, provided it is no more than 0.3 metres high and satisfies the other Class E limits. But not every structure described as a deck will necessarily be analysed in the same way.

Appeal APP/G4240/X/19/3231687 concerned a substantial steel-framed deck with support columns and balustrade. It was attached to the brickwork and combined with existing decking attached to the dwellinghouse. On those particular facts the Inspector treated the proposal as a building forming an enlargement, improvement or alteration under Class A, rather than ordinary Class E decking. It also failed because the Inspector considered the proposal capable of being described as a veranda or balcony.

That decision should not be turned into a rule that every deck touching a house is automatically a Class A extension. Physical attachment is relevant, but scale, structure and the relationship with the dwellinghouse matter. Ordinary low garden decking is expressly contemplated by the Government guidance under Class E; a substantial structurally integrated deck may require a different analysis.

This distinction matters because the Class A rear-extension depth limits apply only where the development is properly treated as a Class A enlargement. They do not create a general 3 metre or 4 metre depth limit for ordinary Class E garden decking. If a proposed deck is large, heavily engineered or structurally integrated with the house, a certificate of lawfulness for proposed works can provide certainty before construction.

Decking cannot be forward of a wall forming the principal elevation of the original dwellinghouse. The wider Class E coverage test must also be met: the total ground area covered by buildings, enclosures and containers within the curtilage, other than the original dwellinghouse, must not exceed 50% of the curtilage area excluding the original house. The Government guidance treats garden decking as a Class E building or structure, so it forms part of that Class E assessment alongside extensions and outbuildings.

On Article 2(3) land, including a conservation area, Class E has an additional restriction: development is not permitted where any part of the decking would sit on land between a wall forming a side elevation of the dwellinghouse and the curtilage boundary. A corner plot is not automatically limited to rear-only decking; apply the principal-elevation, side-land and boundary tests to the actual layout of the house.

When does garden decking need planning permission?

A planning application is more likely to be needed where the deck is more than 0.3 metres high, is forward of the principal elevation, breaches the Class E coverage limit, sits in a restricted position on Article 2(3) land, or the relevant permitted development right has been removed by a planning condition or Article 4 direction.

Flats and maisonettes do not benefit from the ordinary Part 1 householder rights. A substantial engineered structure which is properly analysed as an enlargement or as a veranda or balcony may also fall outside the ordinary Class E decking route.

If you need certainty before construction, see our certificate of lawfulness for proposed works guide.

How is the 0.3 metre decking height measured?

The GPDO defines a raised platform as a platform with a height greater than 0.3 metres, while the Government guidance says garden decking is permitted under Class E only if it stays within that 0.3 metre limit. The wording does not set out a separate detailed surveying method for decking.

There is useful appeal evidence on sloping ground. In APP/G4240/X/19/3231687, the Inspector was satisfied that the proposed decking was less than 0.3 metres above the highest part of the surface of the ground adjacent to it. That supports using the highest immediately adjacent natural ground level where levels vary, rather than measuring every exposed edge from the lowest point of a sloping garden.

Do not confuse that with adding soil, paving or another artificial platform purely to manufacture a higher datum. Where the ground levels have been altered or the difference is material to whether the decking is lawful, the safest course is to establish the pre-existing levels and seek a certificate if necessary.

Decking attached to a home office or other outbuilding

This is acceptable, as long as the decking is not higher than 0.3m. Class E for outbuildings, which are incidental to the use of the dwelling, says it would not be allowed if ‘it would include the construction or provision of a verandah, balcony or raised platform;” The raised platform is over 0.3m or 300mm.

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Page Updated: 2nd September 2026