Appeal 3345805

The appeal is dismissed.

The description of development has been changed on the decision notice to ‘part single, part two storey side and rear extension with terraces and hard and soft landscaping works following the removal of attached garage.’ I have no record of this change being agreed, however, wording on the decision notice accurately reflects the proposals and I have proceeded on this basis.

The Government published a revised National Planning Policy Framework (the Framework) on 12 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 is inappropriate development for the purposes of the Framework and development plan policy; • The effect on the openness of the Green Belt; and • If the development is inappropriate, whether the harm by reason of inappropriateness, and any other harm, is clearly outweighed by the other considerations, so as to amount to the very special circumstances necessary to justify the development.

Development within the Green Belt is considered to be inappropriate unless one of the exceptions within paragraph 154 of the Framework applies. In this case, the proposals need to be considered under part c which allows for extension or alteration of a building provided that it does not result in disproportionate additions over and above the size of the original building.

There is no specific metric in either national or local guidance or policy for determining proportionality. Policy EE14 of the Runnymede 2030 Local Plan (LP) provides considerations to be taken into account when assessing extensions to buildings in the Green Belt. In terms of what is considered to be the ‘original dwelling’ the policy states that the planning history of the site post 1 July 1948 should be taken into account.

The house currently on the site is a replacement dwelling constructed in the 1980s and subsequently extended. However, the original building is the house built on the plot in the 1950s which had a floor area of around 215m2.

The house currently on the site has a gross external area (GEA) of 311.7m2 which is around a 45% increase on the original house (increase from 215m2 to 311.7m2). The proposal would result in the house having a GEA of 348.1m2 which would be around a 62% increase compared to the ‘original’.

The current house is already substantially larger, in terms of floor area, than what was on the site originally. The increase in floor area of around 62% compared to the original is significant and would be disproportionate given that it is more than half of the original floor area.

The consideration of proportionality is not solely measured by floor area or volume increase. Although the proposal would lead to changes in site coverage and result in a narrower house, the extension would appear as a substantial addition to the property, particularly given the increase in mass to the rear and the alterations to the form of the roof.

On this basis, the proposal would represent inappropriate development in the Green Belt and would not accord with the exemption outlined at Paragraph 154(c) of the Framework. It would also conflict with Policy EE14 of the LP which seeks to ensure that the Green Belt is preserved from inappropriate development.

Policy EE14 of the LP states that development proposals should maintain the openness of the Green Belt and not conflict with the purposes of including land within the Green Belt. It also states that development should also not materially increase the prominence of the development on the site. The national Planning Practice Guidance indicates that openness is capable of having both spatial and visual aspects.

The house currently on the plot has a catslide roof to the rear with dormer projections. The proposals would add a dominant addition to the rear of the property. The massing of the building would be increased, particularly at the first-floor level. The inclusion of the terraces/balcony areas and associated balustrades further increase the perceived mass of the building.

Whilst there is intervening vegetation, the house and the proposed extension would be visible from the street, including from the bridge over the river Bourne and near to the driveway of the neighbouring property, ‘Green Shadows.’ Furthermore, the rear of the property can also be seen from neighbouring properties as well as from the [name].

Such a significant increase would erode the openness of the Green Belt and would not be consistent with the purpose of the Green Belt to check the unrestricted sprawl of large built-up areas.

The removal of the garage at ground floor level would reduce the width of the building and compensate for some of the increased floor area. It would also result in the house being further from the side boundary of the plot. However, as the garage is single storey its current impact on openness is more limited than the extension proposed. There is also a detached garage at the front of the plot which would mean there would still be development to the side of the property even if the attached garage were removed.

Overall, the increase in the scale of the building on the site, particularly the two storey elements, would cause a moderate level of harm to the Green Belt in conflict with Policy EE14 of the LP.

Details have been provided of an alternative development for a rear extension and loft conversion with rear dormer window which could be constructed under permitted development. This is confirmed by the issuing of a Certificate of Lawfulness (ref: RU.22/1127). Given that this achieves some of the same aims as the current proposal, albeit on a smaller scale, this constitutes a realistic fallback position which has a greater than theoretical possibility of being completed.

The appellant’s case is that in terms of floor space the permitted development scheme would result in a greater increase in volume than the appeal proposal. Comparisons in terms of volume are made between the removal of the attached garage through demolition, and construction of a dormer window and single storey extension which would be 257.79 m3 and the proposed extension which would have a volume of 232.35m3. Detailed calculations have not been included so it is not clear whether the covered terrace areas on the proposed extensions have been included. In any event, whilst comparisons may be drawn in terms of volumes the physical presentations of the proposals are very different. If the dormer and extension were pursued under the permitted development route there would be no mechanism for securing the removal of the garage. The removal of the garage seems unlikely given there would be no practical reason to do so.

Even if accepting that the garage would be removed, the addition of the rear dormer and single storey extension would appear as very modest additions when compared to the appeal scheme. The dormer would be contained within the existing roof slope. It would also replace existing dormer windows and reduce some of the massing on the first floor. The ground floor extension would also incorporate some of the existing rear extension.

The height of the proposed extension may not be higher than the highest point on the existing house, however, the massing would be greater due to the increase in two storey bulk focused on a single elevation of the building where the catslide roof currently has a much lesser impact. Although the glazing does give the extension a more lightweight appearance and overhanging balcony features may mitigate to some extent, it would still be viewed as a large addition to the property.

Overall, I do not find the fallback option and the appeal proposal to be sufficiently comparable. The large two storey projection and associated balconies and terraces would have a significantly greater impact on openness than the permitted development scheme.

The appellant argues that the appeal scheme would provide a more coherent overall design which takes its cues from and enhances the host building. I do not find the design of the permitted development scheme to have a particularly harmful impact on the character of the building to warrant the Green Belt harm that the proposed extension would introduce. Even if this were the case it would still not outweigh the harm identified.

The proposed disproportionate extensions to the building would constitute inappropriate development in the Green Belt resulting in moderate harm to its openness. Inappropriate development is by definition harmful to the Green Belt. I give substantial weight to the harm to the Green Belt and its openness.

[name] have concluded above, the permitted development extensions carry limited weight. I therefore find that the other considerations in this case do not clearly outweigh the harm arising from the appeal scheme that I have identified. Consequently, the very special circumstances necessary to justify the development do not exist.

The proposal conflicts with the development plan and the material considerations do not indicate that the appeal should be decided other than in accordance with it. For the reasons given above the appeal should be dismissed.