Condition B.2(b) states that to qualify for class B rights, "the edge of the enlargement closest to the eaves of the original roof, shall, so far as practicable, be not less than 20 centimetres from the eaves of the original roof". The Department for Communities and Local Government's technical guidance note Permitted Development for Householders advises that the 20 centimetres should be measured along the roof slope from the outermost edge of the eaves.
This formula was tested in London Borough of Waltham Forest v Secretary of State for Communities and Local Government, in which the council challenged an inspector's decision to quash an enforcement notice requiring the removal of a rear dormer extension at a house in east London. The council contended that the 20-centimetre setback distance should be measured from the inner edge of the eaves - in other words, from the intersection of the back wall and roof of the property.
Applying the technical guidance, the inspector rejected this approach (DCS Number 100-074-491). After referring to various dictionary definitions, the judge was satisfied that the natural interpretation of condition B.2(b) was that the setback should be measured from the closest point of the eaves, at their intersection with the wall. On that basis, he struck down the inspector's decision.
The online version of the technical guidance now includes a footnote saying the department is considering the impact of the court decision and advises householders to "discuss roof extension proposals with their local authority" in the meantime. Given that council planners are probably as confused as anyone, this advice seems of limited utility.
The confusion that arises for applicants was illustrated by an appeal decision last month on an enforcement notice requiring removal of rear roof extensions elsewhere in east London (see the full article). The appellant had carried out further works in an attempt to bring the extensions within the scope of the GPDO, as defined in the technical guidance.
The inspector decided that to require further changes to meet the "correctly defined" setback implied by the court ruling would produce only a marginal visual improvement. He noted that the appellant had plainly made efforts to establish whether the works were lawful "against a confused background at a time of what has been proven to be incorrect technical guidance".