Obtaining authorisation for construction projects can be extremely demanding, but a combination of persistence and the right legal advice will often win the day. In a case on point, a householder whose hopes of building a garden room were time and again thwarted by planners was finally granted his wish by the High Court.

The householder twice applied to his local authority for a certificate confirming that his proposed development was automatically permitted under the terms of the Town and Country Planning (General Permitted Development) Order 1995 (GPDO) and that formal planning permission was therefore not required. His applications were rejected on both occasions and his appeals to planning inspectors were dismissed.

His challenge to that outcome hinged on whether his plans fell within Class E of Schedule 2 of the GPDO. Class E permits the provision within the curtilage of a dwelling any building which is for a purpose incidental to the enjoyment of that dwelling. There was no dispute that the proposed garden room fell within that definition.

However, Class E places tight restrictions on the height and scale of new buildings. Relevant to the householder’s proposal was the requirement that the height of any structure, measured from the ground immediately adjacent to it, must not be more than three metres. Where a building is within two metres of a dwelling’s boundary, and is more than 2.5 metres in height – again measured from the immediately adjacent ground – it is also excluded from Class E.

Ground to the north of the proposed building had been excavated some years previously and the planning inspector who most recently rejected the householder’s case ruled that the height of the planned structure, measured from the existing level of immediately adjacent ground, would exceed three metres. The householder pointed out that the excavated ground would be back-filled in the course of the development. His argument that the structure’s height should be measured from the level of the ground post back-filling was, however, rejected.

Overturning the inspector’s decision, the Court found that the only sensible reading of the relevant parts of the GPDO accorded with the householder’s interpretation. Back-filling formed part of the plans he had submitted and the Court found that the building’s height should be measured from the level of the immediately adjacent ground on completion of the development. That height would be less than three metres.

The south flank of the building would abut a wall marking the property’s boundary and the inspector found that, when measured against the immediately adjoining ground – which could not be back-filled – that part of the structure would exceed 2.5 metres in height.

However, in also upholding the householder’s challenge to that ruling, the Court found that the ground immediately adjacent to the south flank should be taken as being his neighbour’s garden. That was less than 2.5 metres lower than the nearest part of the proposed building.

The Court concluded that the only correct answer to the issues raised by the case was that the proposed development fell within Class E and would thus be lawful development. The Court had no power to substitute its own decision for that of the inspector. However, it remitted the matter for reconsideration by the Welsh Ministers in accordance with its judgment.