Single storey side extension, conversion of double garage to study

Appeal Decision Site visit made on 10 September 2025 by H Miles BA (hons), MA, MRTPI an Inspector appointed by the Secretary of State Decision date: 22nd September 2025 Appeal Ref: APP/H2265/D/25/3369031 5 Legge Lane, Birling, West Malling ME19 5JH • The appeal is made under section 78 of the Town and Country Planning Act 1990 (as amended) against a refusal to grant planning permission. • The appeal is made by Mr and Mrs Thorogood against the decision of Tonbridge and Malling Borough Council. • The application Ref is TM/25/00430/PA. • The development proposed is single storey side extension, conversion of double garage to study. Decision 1. The appeal is dismissed. Main Issues 2. The main issues are: • Whether the proposal would be inappropriate development in the Green Belt having regard to the National Planning Policy Framework 2024 (the Framework) and any relevant development plan policies. • The effect of the proposal on the openness of the Green Belt. • 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. Reasons Whether inappropriate development 3. The Framework states that inappropriate development is, by definition, harmful to the Green Belt. Development in the Green Belt is inappropriate and thus should be approved only if very special circumstances exist, unless it comes within one of the exceptions in the Framework. Policy CP3 of the Core Strategy (2007) (CS) states that national green belt policy will be applied to this site. 4. Of relevance to this appeal, paragraph 154c) of the Framework provides an exception for 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. Neither the Framework nor the development plan policy sets a specific amount for an increase that is considered to be disproportionate. 5. The house at 5 Legge Lane was constructed under planning ref TM/94/0182/FL. I understand that the property was a two storey dwelling with a double garage with Appeal Decision APP/H2265/D/25/3369031 2 pitched roof. The appellant calculates its volume as 899cu.m. and floor area as 264sq.m. 6. The property has subsequently been extended with a single storey extension across the full width of the rear (north-eastern) elevation. As well as a two storey infill extension which appears to link the detached garage to the main house and includes first floor accommodation above. The appellant states that together these result in a total volume of 1261cu.m. and 354sq.m. floorspace for the existing dwelling. 7. The proposed development would be a further addition to the property. Although using the existing garage space as a study would not add any floorspace or volume, this room would be attached to a single storey extension which projects beyond the existing side elevation, close to both the north western and south western boundaries. This would be a further increase of 121cu.m and 45sq.m. to the dwelling. Together the extensions result in around a 54% increase in volume, and 51% increase of floor area from the original dwelling. 8. The proposed building works would result in the house on this site having an extended footprint and mass, running from the two storey gable of the original house, continuing throughout the infilled, two storey L shaped footprint and adding a further addition protruding from this floor area. Whilst the addition is single storey it would extend the building line of the dwelling further north west than the existing house, close to the boundaries and the footprint of the building would occupy the majority of the width of the plot. Whilst the massing of the garage already exists, its extension to the side, in connection with the existing extensions, considerably increases the perceived scale of the dwelling on this site. It would change its character from a modest two storey dwelling with garage to a large house across a sprawling footprint. Although it would only marginally exceed a 50% increase in footprint and volume, in the form proposed this would result in disproportionate additions to the original building. 9. Therefore, the exception in paragraph 154c) would not apply and the proposed development would result in disproportionate additions over and above the size of the original building. Consequently, it would be inappropriate development in terms of the Framework and Policy CP3 of the CS, the aims of which are set out above. Openness 10. Openness has both spatial and visual dimensions. The proposed development would extend the footprint of the building into an area which is currently open. Although the extension would be single storey with a flat roof, and constructed in materials to match the existing dwelling, it would be taller than the existing boundary wall. Along with the land levels and planting it is unlikely to be visible in public views from the road. However, the first floor windows of the properties at 1 and 3 Legge Lane face towards the site and the extension would be seen in these private views. Therefore, there would be harm to openness as a result of the proposed development. 11. Consequently, for the reasons above, the proposed development would be harmful to the openness of the Green Belt. As such, it would be contrary to the Framework in this regard. Appeal Decision APP/H2265/D/25/3369031 3 Other Considerations 12. I am referred to an appeal decision at Glenwood (Ref: APP/H2265/D/23/3334762) which is said to result in an increase of 195% above the original dwelling. In that case the Inspector found that although there was an increase in size, it would also result in the appeal property taking on a neater, more compact, better-proportioned and less sprawling appearance. These circumstances are clearly different to those before me now and therefore this does not alter my decision. 13. The appeal site is within the North Downs National Landscape, and I give great weight to conserving and enhancing landscape and scenic beauty in this area, which has the highest status of protection in relation to these issues. I have a duty to seek to further the statutory purposes of the National Landscape which are conserving and enhancing the natural beauty of the area. The proposed development is a domestic extension located within the boundary of this existing residential garden and would not be seen in public views. As such, there would not be a change to the landscape character as a result of the proposed development and therefore it would conserve and enhance the natural beauty of the area. However, the lack of harm in this regard is a neutral matter. Therefore, even when considered together, the other considerations would not weigh in favour of the development. Green Belt Balance 14. I have concluded that the proposal would be inappropriate development in the Green Belt which is, by definition, harmful. There is also harm to the Green Belt due to the effect on openness. Substantial weight should be given to the harm to the Green Belt. Very special circumstances will not exist unless the harm to the Green Belt and any other harm is clearly outweighed by other considerations. 15. The other considerations advanced by the appellant do not weigh in favour of the development. Consequently, they do not clearly outweigh the totality of the Green Belt harm. The very special circumstances necessary to justify the development therefore do not exist. Conclusion 16. 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. Therefore, for the reasons given above the appeal should be dismissed. H Miles INSPECTOR