Appeal 6000739

The appeal is dismissed.

The development has already taken place generally in accordance with the submitted plans. Therefore, I have determined the appeal based on the works that have been implemented and the plans before me.

Following the submission of the appeal, the Richmond upon Thames Local Plan 2024 - 2039 (LP) was adopted in October 2025. The main parties were given the opportunity to comment on the change in policy context and where received, these comments have been taken into consideration.

The main issue relevant to this appeal is the effect of the development on the character and appearance of the area.

The appeal property comprises a two-storey, brick-built semi-detached dwelling with a tiled, side-gabled roof. The adjoining property shares a similar design, although the appeal property is painted cream while the attached dwelling retains exposed brickwork. Both properties front [address], with substantial gaps between this pair and surrounding dwellings, making their flank elevations prominent within the street scene. The wider area is characterised by predominantly two-storey, brick-built residential dwellings arranged in semi-detached and terraced forms with side gabled pitched roofs. The consistent scale and symmetrical appearance of the semi-detached and terrace dwellings is a positive feature of the area. While rear flat-roofed dormer windows exist locally, they vary in scale, design, and materials and are not a defining feature of the area’s established character.

A Certificate of Lawful Development (CLD) was issued by the Council for a rear dormer roof extension and insertion of 2x rooflights to the front roof slope. However, the rear dormer roof extension that has been built does not accord with the plans that were submitted as part of that application.

The dormer window occupies almost the full width of the rear roof slope, incorporates a parapet wall, and extends to the eaves while projecting above the original ridge line. Full height glazed sliding doors have been installed on the rear elevation, differing to the smaller window approved under the lawful development scheme. The parapet wall is painted cream to match the dwelling, while the remainder of the dormer is finished in hanging tiles.

[address] Extension and External Alterations Supplementary Planning Document (SPD) advises that roof extensions should not dominate the original roof. Normally, a significant area of the existing roof should remain beneath a new dormer and on either side, setting the extension well in from the roof edges.

The dormer window is contained within the rear roof slope. However, in this case, its proportions, parapet wall, and projection above the ridge dominate the original roof form and fundamentally alter the dwelling’s scale and appearance. Although modest in size compared to the dwelling as a whole, it represents a substantial addition to the roof. The cream-painted parapet wall has meant the gable end eaves have not been retained, eliminating the distinction between the roof and the flank wall of the house. As a result, the dormer window has effectively replaced the rear roof slope. This design further accentuates the extended dwelling’s bulk and creates a visually dominant addition that contrasts poorly with surrounding two-storey development and the generally consistent roof forms. From the front, the extension’s projection above the ridge is limited and does not significantly disrupt the symmetrical appearance of the semi-detached pair. However, from side views, the dormer’s scale and design are conspicuous, disrupting the roof form of the host dwelling and remaining clearly visible due to the pattern of development. Although the SPD is only guidance, the departure from its advice has caused harm to the character and appearance of the area.

While the additional height was reportedly required to accommodate the full-height glazed sliding doors, the SPD expects dormer windows to replicate the proportions of existing first-floor windows. Due to its size, the installed glazed sliding doors do not comply, reinforcing the departure from guidance and providing no substantive justification for the design approach taken.

The CLD fallback scheme would also increase the perceived scale of the dwelling. However, as per the guidance in the SPD, it would retain gaps to the roof edges, be set below the ridge and finished in hanging tiles on all sides, thereby preserving the roof form, unlike the current development. For the reasons given above, the scale and design of the as built dormer window conflicts with the guidance set out in the SPD and is more harmful to the character and appearance of the area than the fallback scheme. Although the fallback scheme is a material consideration, I afford it limited weight, as a smaller dormer window would have a less harmful impact on the character and appearance of the area and would not justify the harm I have identified.

Dormer windows in the wider area sometimes extend above the ridge or incorporate parapet walls; however, their planning status is generally unknown. In any event, dormer windows of comparable scale and design are rare nearby, and the circumstances of each proposal are likely to be different and are often found in less visible locations. The fact apparently similar development has been built elsewhere is not a reason, on its own, to allow unacceptable development. Each case must be assessed on its merits, and in this instance due to the scale and design of the dormer window and the location of the appeal property, the development is harmful to the character and appearance of the dwelling and its surroundings.

For the reasons given above, the development harms the character and appearance of the area and conflicts with LP Policy LP28. This expects developments, amongst other matters, to achieve high architectural and urban design quality.

Consequently, the development conflicts with the development plan and the material considerations do not indicate that the appeal should be determined other than in accordance with it. Therefore, I conclude that the appeal should be dismissed.