Appeal 3283794

The appeal is allowed and planning permission is granted for a basement level side extension at [site address] in accordance with the terms of the application, Ref 21/02601/HOU, dated 17 May 2021, subject to the following conditions:

The development hereby permitted shall begin not later than 3 years from the date of this decision.

The development hereby permitted shall be carried out in accordance with the following approved plans: 1010 P02 ([name]); 1050 P03 ([name]); 1110 P04 ([name]) and 1150 P04 ([name]).

The site lies within an area of Green Belt. Therefore, the main issues are: • Whether the proposal amount to inappropriate development in the Green Belt; • The effect on the openness of the Green Belt; • If the development is inappropriate, whether any harm by reason of inappropriateness, and any other harm, is clearly outweighed by other considerations so as to amount to the very special circumstances necessary to justify it.

Paragraph 149 of the National Planning Policy Framework (July 2021) (the Framework) states that the construction of new buildings within the Green Belt is inappropriate development but lists certain forms of development which are not regarded as inappropriate. This includes the extension or alteration of a building provided that it does not result in disproportionate additions over and above the size of the original building.

The Council’s decision notice cites conflict with Policy SC7 of the Council’s Core Strategy (July 2017) (the CS). This policy relates to the Green Belt but is concerned with the release of Green Belt land and review of its boundaries, rather than individual applications for development in the Green Belt. As such, the policy is of limited relevance to the present appeal, and I have assessed the proposal primarily against the Framework test.

The appeal relates to a detached dwelling located in an isolated position on [site address] to the west of the village of Menston. The dwelling sits on a sloping site, with the basement level accessible from outside at the rear. The dwelling has been subject to past extensions, notably a flat roofed single storey garage extension to the rear at basement/garden level, above which is a terrace and smaller single storey extension. A glazed conservatory stands to one side of the dwelling and a small porch exists on the front elevation. The proposed extension would be located at the basement/garden level within the space between the existing garage and conservatory.

The Council considers that the proposed extension, taken together with previous extensions, would result in disproportionate additions over and above the size of the original building. There is dispute as to the extent of the original building, its volume and that of the various extensions. The Council in its officer report considers the existing extensions have increased the original volume of the dwelling by some 34% and would become some 42.5% with the addition of proposed extension.

I note correspondence between the main parties following the Council’s decision where these figures were challenged, with the appellant subsequently producing a [name] (VJR) which sets out the existing and proposed volumes based on different assessments. This report was subsequently submitted in support of a later application for the same development, also refused (Council Ref 21/04954/HOU). I am provided with the Council’s officer report for this application, which provides more detailed response to the VJR.

From this, I glean that there is now common ground that the volume of the basement should be included in the calculations. The Council accepts that this would have formed part of the dwelling as originally built or as existed on 1 July 1948. This would accord with the guidance of the Householder Supplementary Planning Document (April 2012) (the HSPD) and the Framework definition of ‘original building’. On site, I saw that the basement contains several rooms forming an integral part of the dwelling, and I see no reason to discount the volume of the basement from the calculations.

This being the case, the Council puts the original volume at 938 cubic metres, and calculates the combined existing volume of extensions at 272.4 cubic metres (a 29% increase) and the proposed volume at 327.4 cubic metres (a 34.9% increase).

However, within this the Council includes the ‘volume’ of the rear terrace by calculating the volume of airspace within the dimensions of the terrace railings. However, the railings are transparent, and there is no other physical built form to what is an open terrace, not including the single storey extension which is separately calculated. Consequently, beyond the nominal volume of the railings themselves, I am not convinced that this airspace amounts to additional physical volume to be factored into the calculations.

The appellant also points to outbuildings which existed on site as far back as

Those now on site are detached structures within the garden at a distance from the main dwelling. However, the Council questions whether the outbuildings now on site are those which existed in 1948, or whether they have always formed part of the curtilage of the dwelling. I do not have firm evidence as to how these outbuildings were used and whether they amounted to normal domestic adjuncts. This aside, the separation distances to the main dwelling mean I am not persuaded that these outbuildings should be considered as extensions to the main dwelling. Accordingly, I favour the calculations which omit the volume of the outbuildings.

Given these differences between the parties, the appellant’s VJR has set out calculations for different scenarios with the aforementioned elements being either included or excluded. As these appear to have been calculated electronically, and include breakdowns of each extension, I consider these to be robust. The figures show that the cumulative increase in volume from extensions, including the proposal, would be between 29% (when the outbuildings are included) and 36% (using the Council’s initial approach of considering above ground volume only). Given my considerations above, Scenario 3 of the VFR represents the most relevant calculation, and would result in a cumulative increase of 31%.

The Framework does not specify what might be a disproportionate addition over and above the size of the original building. The HSPD states that ‘Where proposals result in an addition of over 30% of the original cubic volume, they are likely to be considered disproportionate.’ However, the word likely implies that exceedances of the threshold are not automatically disproportionate, and whilst I note the 30% threshold, the assessment of whether the proposal would amount to ‘disproportionate additions’ is ultimately a matter of judgement based on the particular facts in each case.

The cumulative increase in volume of 31% in this case would only marginally exceed the HSPD threshold. Indeed, even including the volume of the terrace as the Council has, the threshold would only be exceeded by a limited margin at 34%. In my view, none of the scenarios outlined in the VJR or the Council would result in a disproportionate increase in volume.

That the existing extensions are not disproportionate in size is evident when viewing the dwelling. The majority of added volume has been at low level to the rear, principally the garage extension. The extensions above this at the ground level are modest in scale and subservient to the main dwelling. The proposed extension would also be at low level, beneath a green roof, with a modest footprint. It would not alter the main body of the dwelling at ground and first floor levels and its original form would continue to be legible.

Given this, and having regard to the totality of evidence put to me, I find that the existing extensions are not disproportionate in size, and the addition of the proposed extension would not result in disproportionate additions over and above the size of the original building. Therefore, the proposal would not amount to inappropriate development in the Green Belt and would not conflict with the relevant provisions of the Framework.

With respect to openness and the purposes of the Green Belt, given my findings that the proposal would not be inappropriate development in the Green Belt, the proposal would, by definition, not have an adverse impact on the openness of the Green Belt or the purposes of including land within it.

As the proposal does not amount to inappropriate development, there is no requirement to assess if there are other considerations that amount to very special circumstances needed to justify the development.

The Council did not oppose the design of the extension, and having regard to the proposed position, form and materials, I am satisfied that it would preserve the character and appearance of the host dwelling and wider area. The submitted plans also include proposed replacement of the conservatory glazing without change to its overall size or shape. Consequently, there would be no material effect on openness as a result. The Council has not opposed these works and, on the evidence before me, I have no reasons to disagree.

There are no near neighbours to the site whose living conditions could be affected by the proposal, nor would the proposal affect existing parking or access arrangements.

I have found above that the proposal would not be inappropriate development in the Green Belt, nor would there be a harmful effect on the openness of the Green Belt or the character and appearance of the area. Consequently, there is no conflict with the development plan or the Framework and so the appeal should succeed.

The appeal is therefore allowed, subject to a condition requiring development to be carried out in accordance with the approved plans, to provide certainty.