The garden room would be largely underground, built into the land sloping down close to the back of the house, the inspector noted. It was not disputed that it satisfied all the conditions of Class E, Part 1, Schedule 2 of the GPDO. The council argued, however, that building the garden room would involve significant engineering works in digging out the sloping site and that these works could not be considered to be permitted development. It pointed to the need to excavate up to a 2.5m depth of material close to the rear of the house to create a floor level extending 10m out from the house.
The need to provide engineering calculations and design for the structure showed that significant operations would be involved, the council contended, and they would require formal planning permission.
The inspector remarked that whilst the council did not make out that the garden room would not comply with the permitted development rights set out in Class E, it had separated the excavation works as significant engineering operations which would require planning permission. He ruled, however, that the fact that substantial engineering works might be required did not disqualify the proposal from being permitted development, pointing out that Class E allows for the provision of a swimming pool which could require earthworks on a similar scale.
Inspector John Whalley; Written representations