Appeal 3338197

The appeal is dismissed.

The ‘National Planning Policy Framework’ was revised in December 2023 but, in this instance, the issues most relevant to the appeal remain unaffected by the revisions that have been made to it. I am therefore satisfied that there is no requirement to seek further submissions on the revised ‘Framework’, and that no party would be disadvantaged by such a course of action. In this appeal, I have had regard to the most recent version.

The main issues in this appeal are: • Whether the proposal would be inappropriate development in the Green Belt having regard to the ‘National Planning Policy Framework’ and any relevant development plan policies. • The effect of the proposal on the openness of the Green Belt. • The effect of the proposal on the character and appearance of the host building and its surroundings in the Heronsgate Conservation Area. • 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. Appeal Decision: APP/P1940/D/24/3338197

If the proposal would not amount to inappropriate development in the Green Belt (in terms of Green Belt policy), it is nonetheless necessary to consider the effect of the proposal on the character and appearance of the host building and its surroundings in the Heronsgate Conservation Area.

Heronsgate is a residential area, at the edge of Chorleywood in Hertfordshire. The appeal site is located within the Metropolitan Green Belt, which “washes over” the settlement. ‘Virginia’ is a substantial house, located towards the end of [site address] , in the south-western part of the settlement.

It is proposed that the existing detached garage that is located close to the house should be demolished and that new extensions should be added to the house, partly single-storey and partly two-storey.

The ‘National Planning Policy Framework’ makes it plain, at paragraphs 152- 156, that the construction of new buildings is not normally acceptable in the Green Belt and that they should only be permitted in “very special circumstances”, subject to certain exceptions. Nevertheless, an extension to an existing building in the Green Belt can be considered to be not inappropriate, “provided that it does not result in disproportionate additions over and above the size of the original building”.

Key policies in the Development Plan are to be found in the Three Rivers District Council planning policy documents: the ‘Local Development Framework Core Strategy’ (which was adopted in October 2011) and the ‘Development Management Policies Local Development Document’ (which was adopted in July 2013).

Policy CP11 of the ‘[name] underpins the national planning policy relating to the Green Belt. The ‘[name] refers to the pressure on the Green Belt within the District and Policy CP11 emphasises the general presumption against “inappropriate” development.

Policy DM2 in the ‘Development Management Policies’ provides more detail in relation to Green Belt Policy as it affects extensions to existing buildings. It provides that extensions which are “disproportionate in size” will not be permitted, although it goes on to identify certain other considerations that are to be taken into account in making an assessment. These may be summarised as: the building’s proximity and relationship to other buildings, its prominence in the setting and the effect on openness.

In undertaking my assessment of whether the appeal proposal is inappropriate development, I find that the proposed extensions would add very substantially to the size of the existing house, increasing the volume of building in the Green Belt. Green Belt policies do not impose a mathematical approach to the determination of what may be considered to be disproportionate, however. While the Council suggests that a cumulative increase in floorspace of more than 40% may be considered to be disproportionate, this formula derives from an old, superseded, ‘Supplementary Planning Document’ and is not determinative. 2 Appeal Decision: APP/P1940/D/24/3338197

Both the Council’s ‘[name] and their ‘Development Management Policies’ take a more flexible approach, as does the ‘National Planning Policy Framework’.

In this case, I find that, cumulatively, the proposed extensions would be disproportionate in size by comparison with the existing house. The scale and volume of the proposed extensions are such that they are ineligible to be considered as falling within the exception that is set out in paragraph 154(c) of the ‘National Planning Policy Framework’. In my view, the additions would be “disproportionate” and the proposals must therefore be categorised as “inappropriate” in terms of the application of Green Belt policies.

In undertaking my assessment of whether the appeal proposal would have an impact on the openness of the Green Belt, I am conscious that in visual terms the site is well screened and is not prominent in the setting, while the finished house would be clearly separated from nearby buildings. Nevertheless, there would be a greater volume of building within the Green Belt, creating a spatial impact on openness, even though the new extension would be well screened, limiting its visual impact on openness. It follows that, in planning terms, “harm” would be caused by reason of inappropriateness and conflict with Green Belt policy and that the openness of the Green Belt would be eroded.

In terms of design, the existing house is traditional in form, a mainly two-storey building constructed of brickwork under a hipped main roof. It appears to have been previously extended and it has a garage outbuilding. The house itself is a substantial property with a very large garden that is well screened by a mature hedge along the front boundary.

The finished bulk of the principal building on the site would create bland and massy elevations on the north-east and north-west of the building. The single-storey extension on the north-east would create a large and ungainly element, with an uncharacteristically shallow roof pitch. The design would not be in keeping with the existing host building.

For these reasons, I find that the appeal proposal would have a harmful effect on the character and appearance of the host building.

The ‘National Planning Policy Framework’ emphasises the aim of “achieving well designed places” in the broadest sense (notably at Section 12), while making effective use of land and encouraging economic activity. It is aimed at achieving good design standards generally, by adding to the overall quality of the area and being visually attractive and sympathetic to local character and history (while not preventing or discouraging appropriate innovation or change), although it is also recognised that appropriate change may include increased densities.

Policy CP12 of the ‘[name] is a general Policy that encourages good design in broad terms while including the aim of conserving and enhancing heritage assets specifically (among other things). Policy DM1 and Appendix 2 in the ‘Development Management Policies’ address design considerations generally. In view of my design related findings, the appeal scheme conflicts with both of these Policies and with the Framework. 3 Appeal Decision: APP/P1940/D/24/3338197

In terms of heritage considerations, the appeal property is one of the later additions to the Heronsgate Conservation Area. Its immediate neighbours are houses and gardens that can also be described as large properties in extensive grounds, although there is an open grassy area opposite ‘Virginia’ itself.

Heronsgate has a somewhat rural character, in a setting that is enhanced by mature gardens with well grown trees and hedges. Within the locality, the internal roads are rather narrow for the most part, deriving from its nineteenth century origins (as explained in the ‘Heronsgate Conservation Area Appraisal’ dated 2012), often encroached upon by boundary hedges, and individual houses are generally secluded properties on large plots. There are some historic buildings within the area (including some listed buildings) and more modern individual houses have usually been designed in traditional forms, often with an “Arts & Crafts” flavour, adding to the rural character and charm of the settlement. The significance of this designated heritage asset is mainly historically and architecturally derived.

Provisions in the Planning (Listed Buildings and Conservation Areas) Act 1990 (“the Act”) impose obligations on those considering whether to grant planning permission to pay special attention to the desirability of preserving or enhancing the character or appearance of conservation areas affected by development proposals (specifically at Section 72 of this Act).

Those formal requirements relating to conservation areas are reinforced by the ‘National Planning Policy Framework’, especially at Section 16, which emphasises the importance of conserving or enhancing the historic environment, though it also points out the desirability of putting a heritage asset to its “optimum viable use” as does the ‘Planning Practice Guidance’.

Policy DM3 in the ‘Development Management Policies’ also focusses on “The Historic Built Environment” and it includes provisions relating to conservation areas within the District. Again, it reflects national planning policies (and legislation), in providing that planning permission will only be granted for development that “preserves or enhances the character or appearance of the area”.

The harm to the host building identified above would have a harmful effect on the character and appearance of the Conservation Area as a whole. The finished building would be an unattractive element within it, undermining its significance.

In the context of the ‘National Planning Policy Framework’, that harm would be “less than substantial”. However, when considering the impact of a proposed development on the significance of a designated heritage asset, great weight should be given to the asset’s conservation (and the more important the asset the greater the weight should be). This is irrespective of whether any potential harm amounts to “substantial harm”, total loss or “less than substantial harm” to its significance.

This harm would fail to either preserve or enhance the character and appearance of the Conservation Area. Thus, it would fail to meet the provisions of the Act. 4 Appeal Decision: APP/P1940/D/24/3338197

The contribution that the appeal scheme would make to economic activity and the additional residential accommodation that would be created both carry some weight in favour of the appeal, since the national housing stock would be increased, albeit in a very limited way. Indeed, it is noted that the scheme could accommodate an elderly relative. No other public benefits have been identified.

In the context of the assessment required by paragraphs 206 and 208 of the ‘National Planning Policy Framework’ the harm to the Conservation Area would clearly outweigh the public benefits. Thus, the appeal proposal would conflict with the approach to heritage assets as set out in both national and local policies, including, specifically, Policy DM3 of the ‘Development Management Policies’.

In accordance with paragraph 152 of the ‘National Planning Policy Framework’, inappropriate development is, by definition, harmful to the Green Belt and should not be approved except in “very special circumstances”. Such 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 case, I have concluded that the proposed extensions would result in “disproportionate additions over and above the size of the original building” and that the development would thus be harmful to the Green Belt in principle. The appeal scheme would also be harmful in terms of the openness of the Green Belt. Furthermore, the scheme would harm the character and appearance of both the host building and the Heronsgate Conservation Area and would conflict with the Act in regard to the latter. These each pose conflicts with national and local policies, weighing heavily against the appeal scheme.

The appeal scheme would entail limited public benefits. No other considerations have been advanced that would weigh in favour of the appeal proposal. Consequently, the potential harm to the Green Belt by reason of inappropriateness, and any other harm resulting from the proposal, is not clearly outweighed by other considerations. Therefore, “very special circumstances” do not apply here. Hence, the appeal proposal conflicts with both the approach to the Green Belt set out in the ‘National Planning Policy Framework’ and in the Development Plan (notably at Policies CP11 and DM2 referred to above).

In view of my findings, the scheme before me would conflict with both national planning policies and the Development Plan as a whole. There are no matters before me that would outweigh that conflict and I have no doubt that the appeal should be dismissed.