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Appeal Decision 198 - Certificate of Lawful Development.

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January 2011 - Code a00198


Summary of Case (appeal dismissed): 


The property is a two-storey semi-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, albeit with the ridge-line of the former at a lower level than the ridge-line of the latter. The application proposed to convert the hipped end of the main roof (part of which covered by the attached roof of the extension) into a gable end, and to erect a large 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 Inspector stated the following: 


“The appellant’s agent and the Council agree that the volume of roof extension involved in the hip to gable and the new rear dormer would be 36.41 m: in total. The difference between the two parties is in the additional calculation of the volume of roof over the existing two storey extension. This is an alteration/addition to the original roof and its volume must be included in the calculation. 


Further, the difference between the two parties is quite close with the appellant calculating the volume of the existing roof at 14.28 m:, giving rise to a total volume of 49.53 m:, whereas the Council estimate the existing roof to be 19.72 m:, giving rise to a total volume of 56.13 m: 


In considering these differences a number of aspects concern me. Firstly, the Council appear to have used measurements scaled from copies of the plans rather than the appellant’s dimensions as stated on the plans. However, not all the relevant dimensions are included on the plans, and in particular there is insufficient information to properly calculate the awkward three dimensional shape of parcel ‘1’. This has led to both parties having to estimate the external volume of this space. Further, the appellant’s agent appears to have used an incorrect formula for calculating the volume of parcel ‘2’. 


Given that the decision as to whether the volume of the total additions to the roof exceeds 50 m: may turn on a very fine degree of calculation, I am not satisfied that sufficiently detailed information has been submitted for the parties to be able to reach a clear and unequivocal conclusion on the total volume of the existing and proposed work. The advice in Circular 10/1997 highlights that in such LDC applications, the onus lies on the appellant to provide sufficient evidence to establish their case. On the balance of probability, I find that the claim of lawfulness has not been established to a proper degree.” 


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)].


·       Furthermore, even if the roof of the existing extension doesn’t contain any dormers / rooflights / habitable rooms / etc, this will still 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)].


·       In an application for a certificate of lawfulness, the burden of proof is firmly on the applicant.
[Relevant to: "General”].


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


·       Appeal Decision Notice: 

·       OS Map: 

·       Existing Drawings: 

·       Proposed Floor Plans: 

·       Proposed Elevations: 

·       Proposed Roof Plan: 




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