Appeal 3349362

The appeal is allowed and planning permission is granted for Single storey rear extension at Chedley, [site address] , Denham [postcode] in accordance with the terms of the application, [name]/24/0842/FA, subject to the following conditions:

The development hereby permitted shall begin not later than three years from the date of this decision.

The development hereby permitted shall be carried out in accordance with drawing no’s: 19/474/001 Site Location and Block Plan; 19/474/002 [name] and Elevations; and 19/474/003 [name] and Elevations.

The external materials of the extension hereby permitted shall match those used in the existing dwelling.

The Government published a revised National Planning Policy Framework (the Framework) in December 2024. Those parts of the Framework most relevant to this appeal have not been amended. As a result, I have not sought submissions on the revised Framework, and I am satisfied that no party’s interests have been prejudiced by taking this approach. Where references are made to paragraph numbers of the Framework, these are references to the most recent version.

The main issues are: • whether the proposal would be inappropriate development in the Green Belt; • the effect of the proposed development on the openness of the Green Belt; and • whether any harm by reason of inappropriateness, and any other harm, would be clearly outweighed by other considerations so as to amount to the very special circumstances required to justify the proposal.

Paragraph 142 of the Framework states that the fundamental aim of Green Belt policy is to prevent urban sprawl by keeping land permanently open; the essential characteristics of Green Belts are their openness and their permanence.

The Framework at paragraph 153 is explicit as it states that substantial weight is given to any harm to the Green Belt, including harm to its openness. Paragraph 154 of the Framework states that development is inappropriate in the Green Belt unless it falls within the given list of exceptions. Exception c) advises that provided extensions or alterations to dwellings do not result in disproportionate additions over and above the size of the original building then extensions would not be inappropriate development.

Policies GB1 and GB10 of the South Bucks Local Development Framework Core Strategy Development Plan Document, adopted February 2011 (the [name]) reflect elements of the Framework. GB1 gives a list of forms of development that are not inappropriate which includes extensions to existing buildings. Exception e) of GB1 sets out that are extensions should be limited. Core Strategy Policy GB10 provides further guidance on the scale of extensions to existing dwellings in the Green Belt. This seeks to ensure that extensions are integral to and small scale in relation to the size of the original dwelling.

The Council states that the proposed extension, combined with previous extensions would represent a 81% increase in floor area over the original building. The supporting text advises that where the result of the development is that the original dwelling has increased its floorspace by more than half, that this is not regarded as small scale.

A cumulative increase in floorspace of this scale would not be considered to be proportionate in the context of the size of the original dwelling, and furthermore, the increase in built form would result in greater visual bulk. However, although the proposed extension is relatively low in height, and subservient to the dwelling, this would represent a large extension and disproportionate addition over and above the size of the original building.

I conclude that the proposal would therefore be contrary to [name] GB1 and GB10 which together seeks to ensure extensions to dwellings in the Green Belt are limited and small scale in comparison to the original dwelling. However, although these are not wholly consistent with the Framework, the proposal would be inappropriate development in the Green Belt and would conflict with Paragraph 153 c) of the Framework. This sets out that inappropriate development is, by definition, harmful to the Green Belt and should not be approved except in very special circumstances.

The considerable increase in floorspace, length and volume means the proposal would have a material impact on openness in a spatial aspect. The development would be noticeable to occupiers of adjacent dwellings, particularly within their gardens. There would also be a material impact on the visual openness of the Green Belt.

The above effects would be alleviated by the side boundaries being screened with mature vegetation and fencing. A small part of the proposal would also be screened by the host building itself. As the development would be located to the rear of the property, it would not feature prominently in the streetscene. The appeal site is also of a significant length and width. As a consequence notwithstanding immediate neighbouring residents, the development would not be very publicly visible or discernible beyond the site.

The Council has not identified any harm to the five purposes of including land within the Green Belt set out in paragraph 143 of the Framework. For similar reasons to those set out above I do not consider it would conflict with any of specified purposes.

I conclude that the proposed development would result in an adverse impact on both the spatial and visual openness of the Green Belt. However, given the above mitigating factors, this impact would result in only very minor harm to the openness of the Green Belt.

The Framework highlights that inappropriate development is, by definition, harmful to the Green Belt and should not be approved except in very special circumstances, with substantial weight given to any harm to the Green Belt. Very special circumstances will not exist unless the potential harm to the Green Belt by reason of inappropriateness, and any other harm resulting from the proposal, is clearly outweighed by other considerations.

In this regard, the appellant has drawn my attention to a fallback position through the Permitted Development process emphasising that extensions to the main dwelling could be erected under Schedule 2, Part 1, Class A of The Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended) (the GPDO).

Of particular relevance is the fact that the appeal property benefits from a prior approval notice (Council reference PL/23/3992/PNE). This was granted in compliance with Schedule 2, Part 1, Class A of the GPDO for an eight-metre single storey rear extension in March 2024.

The two schemes are broadly comparable in design and height. The main difference between the two scheme is the overall width of the extension. The prior approval scheme leaves a gap of 1.3m to the existing two-storey rear extension. The Council correctly highlights that the prior approval scheme would lead to a smaller increase in footprint, by approximately 10 sqm. Thus there would be a reduced impact on spatial openness.

However, the site specific factors of the proposal and appeal site locate the additional volume and footprint between two built elements. It would not extend any further into the rear expansive garden towards the countryside. In effect the additional floorspace is a narrow amount of development, which would not be significantly more discernible to neighbouring residents than the prior approval scheme. Given the likely limited visibility of the proposal beyond the appeal site, the difference between the two schemes on the visual openness would be negligible in this regard.

The removal of a narrow and awkward gap would result in a more cohesive rear elevation, and as a personal benefit would result in a more practical living arrangement. I am of the view that the appeal proposal would, on balance, rearrange the rear elevation more successfully than the prior approval scheme, which adds weight in favour of the proposal.

The Courts have held that in considering the concept of a fall-back development as a material consideration, there should be a real prospect of it being implemented, and not just a theoretical possibility that the development might take place. In this regard, there is no clear evidence to support a conclusion that the fallback scheme would not be implemented in the event that the appeal was dismissed. I am satisfied that there is a real prospect of the fallback development taking place and I attach very substantial weight to this consideration.

The Council has not identified any concerns regarding the effect of the proposal on the character and appearance of the host dwelling, the area or upon the living conditions of neighbouring residents. I do not disagree with these assessments.

I consider that the development is contrary to the development plan, however the Council’s policies do not refer to very special circumstances as set out in the Framework, thus the conflict is of limited weight. Nonetheless, substantial weight is given to the harm to the Green Belt by way of its inappropriateness and harm to its openness.

Given the similarities between the schemes, and likely effects I have taken into account the impact of the permitted development fallback position. I have attached very substantial weight to this. In this particular case the weight attributed to the other considerations and benefits clearly outweigh the very minor harm I have identified to openness. I conclude there are very special circumstances to justify the development such that the proposal would accord with the provisions of paragraph 153 of the Framework.

I have considered the Council’s suggested conditions against the advice on conditions set out in the Framework and the Planning Practice Guidance. I have imposed the standard conditions relating to the commencement of development and specifying the relevant plans in order to provide certainty.

I have also imposed a condition requiring the materials to be used in the construction of the external surfaces of the development match those used in the existing building in order to protect the character and appearance of the host dwelling and surrounding area.

The proposed development would conflict with the development plan but material considerations, which include the provisions in the Framework, indicate that a decision should be made other than in accordance with it. I therefore conclude that the appeal should be allowed. [name]