20cm Rule - New Permitted Development Rights - 6 April 2014


Following an appeal case allowed by the Planning Inspectorate against an enforcement notice served on my client relating to their (PD) loft conversion with rear dormer window, it was subsequently challenged by Waltham Forest Council [Waltham Forest LBC v Secretary of State for Communities and Local Government (QBD), 18 June 2013]. The High Court's decision was in favour of the Council's interpretation of the 20cm rule and its measurement and definition of 'eaves'.

Interesting to note however is that the recent changes to permitted development legislation that came into force on 6 April 2014 does not take account of the High Court's Judgement. It appears the court's decision has been buried by the government in which case we are back to the old interpretation, so the old is the new.

See extract from current legislation below relating to Class B of Town and Country Planning (General Permitted Development) (Amendment and Consequential Provisions) (England) Order 2014, which sets out the current legislative position:

In Class B—

for paragraph B.2(b) substitute—

“(b) the enlargement shall be constructed so that—

other than in the case of a hip-to-gable enlargement or an enlargement which joins the original roof to the roof of a rear or side extension —

the eaves of the original roof are maintained or reinstated; and 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, measured along the roof slope from the outside edge of the eaves; and

other than in the case of an enlargement which joins the original roof to the roof of a rear or side extension, no part of the enlargement extends beyond the outside face of any external wall of the original dwellinghouse;

The new legislation still promotes the old DCLG “Permitted Development for Householders - Technical Guidance” document above in relation to condition B.2(b) of Schedule 2, Part 1, Class B of the GPDO 1995, which measures 'along the roof slope' instead of 'set back from the rearmost wall edge' or 'point of intersection with the wall'. The attached shows the relevant guidance and my understanding of the Courts' judgement (in dotted red line).

Unfortunately even after a High Court decision this is still a grey area and until such point as guidance indicates otherwise, it is unclear whether LPA's would determine applications for PD loft conversions in line with the conclusions of the appeal decision or new legislation.

My opinion is, as it has always been, that the 20cm set back should be measured along the roof slope from the outer edge of the projecting eaves (as advised by the DCLG Technical Guidance document) and not from an 'imaginary line' from the wall intersection as advised by Waltham Forest planners.

For clarification on future PD applications, some LPA planners have already agreed with my understanding however it would be good to get further input from other professionals. Ultimately the new GPDO legislation seems clear and consistent with previous guidance.


Erich Wessels B.Sc Town Planning

Planning & Projects

Architectural & Planning Consultants


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Rajan Arora 1 Year Ago - Edited

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