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Appeal Decision 205 - Certificate of Lawful Development.

This appeal decision summary and assessment has been produced by Planning Jungle Limited.  For more information, please go to


January 2011 - Code a00205


Summary of Case (appeal allowed): 


The property is a two-storey detached house with a hipped main roof. The property has previously been extended with a two-storey side extension. The hipped roof of the extension joins onto the main hipped roof, with the eaves and ridge-line of the former at the same level as the eaves and ridge-line of the latter. The application proposed a rear dormer. 


The key issue was whether the proposed enlargement of the roof would be contrary to Class B, part B.1(c), which states that “Development is not permitted by Class B if … the cubic content of the resulting roof space would exceed the cubic content of the original roof space by more than— (i) 40 cubic metres in the case of a terrace house, or (ii) 50 cubic metres in any other case”. 


The Council’s delegated report stated that the “dormer volume” would be 14.1375m3, the “Roof Volume of Existing Two Storey Side Extension” was already 83.79m3, and therefore the “total” volume would be 97.9275m3. The Council therefore refused the application. 


The Inspector stated the following: 


“The plan submitted with the application had discrepancies between the 1:50 and 1:100 scaled plans, elevations and sections in relation to the size of the proposed dormer. The appellant has subsequently confirmed that the external dimensions of the dormer would be 3.8m wide x 2.3m high x 2.4m deep. Based on these dimensions the volume would be 10.45 cubic metres. 


There has been no challenge to the dimensions given for the existing extension which has a roof volume of 38.8 cubic metres. This includes the roof directly above the extension and the additional section of roof that links it to the original roof of the main house. The total volume of additional roof space with the new dormer would therefore be 49.25 cubic metres. As this is within the 50 cubic metres permitted by the GPDO, I conclude that a dormer of the size proposed would be permitted development.” 


Main Conclusions: 


·       Where there is an existing extension with a roof that joins onto the roof of the main house, then this will reduce the volume allowance that remains for roof extensions under Class B, part B.1(c).
[Relevant to: “Interaction between Class A, Class B, and Class C”, Class A, A.1(i), Class B, B.1(c)].


Links to the “Appeal Decision Notice” and other associated documents (e.g. drawings, etc): 


·       Appeal Decision Notice: 

·       OS Map: 

·       Drawings: 

·       Council’s Delegated Report: 




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