I'm currently planning to create a car parking space (classed as an enclosure and class F for PD) at the side of the house. This will entail excavating the roadside retaining wall and ground which is currently an elevated (2.35m) patio area down to road level. Dimensions are 5m long x 5m wide x 2.35m deep. The local council are saying we need planning permission as the new retaining wall positioned at the rear of the parking area will be higher than 2m and is therefore "engineering works" so has to have permission. To us this doesn't make sense as we could erect a building under PD to a height of 2.5m to the eaves. In these circumstances why would it be OK to erect the building under class A PD and not a retaining wall under class F? Thanks to anyone who can confirm.
