Single-storey rear extension with formation of a rear courtyard and replacement windows and door

Appeal Decision Site visit made on 14 April 2026 by R C Shrimplin MA(Cantab) DipArch RIBA FRTPI FCIArb MCIL an Inspector appointed by the Secretary of State Decision date: 01 May 2026 Appeal Reference: 6005170 18 Hooper Street, Cambridge, Cambridgeshire CB1 2NZ • 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 T. Lau against the decision of Cambridge City Council. • The application reference is 25/04554/HFUL. • The development proposed is described in the application form as a “Single-storey rear extension with formation of a rear courtyard and replacement windows and door”. Decision 1. The appeal is allowed and planning permission is granted for a “Single-storey rear extension with formation of a rear courtyard and replacement windows and door”, at 18 Hooper Street, Cambridge, Cambridgeshire CB1 2NZ, in accordance with the terms of the application (reference 25/04554/HFUL), subject to the conditions set out in the attached Schedule of Conditions. Main issues 2. The first main issue to be determined in this appeal is the effect of the proposed development on the character and appearance of the host building and its surroundings in the Mill Road Conservation Area. The second is the effect of the proposed development on the residential amenities of neighbours (whether unacceptable harm would be caused by overbearing appearance or visual dominance). Reasons 3. The appeal site is located in a central part of the City of Cambridge, in an area of closely built-up Victorian housing, with narrow streets and modest terraced houses, but with good sized gardens and some green spaces. The locality has good access to the City Centre and to other local facilities, for example in Mill Road. This is a very pleasant residential environment, and the site lies within the Mill Road Conservation Area. There is considerable pressure on parking in the surrounding streets, however. 4. Number 18 Hooper Street has two bedrooms on the first floor (with a bathroom opening off one of the bedrooms), and a “through” living room occupying the main part of the ground floor, with a kitchen at the rear. The house is constructed on the edge of the footpath, of brickwork under a slate roof, and it is unassuming in design and detailing, in harmony with neighbouring houses in the terrace and with the Appeal Decision: 6005170 2 surroundings more generally. In the ‘Mill Road Conservation Area Appraisal’, it is shown as a “positive unlisted building”. 5. It is now proposed to construct a single-storey rear extension to create an open space at the rear of the ground floor, projecting into the back garden. The floor plan would be irregular, around a small, largely internal, rear courtyard, and it would also involve the replacement of existing windows and a door as well as the removal of an existing side window. The floor plan on the first floor would also be reconfigured, to create a new bathroom, independently accessible from the landing, and a small rear bedroom or study. 6. 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, although it is also recognised that appropriate change may include increased densities. The achievement of good design includes protecting existing residential amenities and providing good standards of accommodation in new development. 7. Policies in the Development Plan also share these basic principles. Notably, in relation to this appeal, Policies 55, 58 and 61 of the ‘Cambridge Local Plan’ (which is dated 2018) address the need to achieve good standards of design, especially in the context of the historic environment (including conservation areas). Moreover, Policy 58 is specifically concerned with “Altering and extending existing buildings” and it includes a provision that such extensions should not “unacceptably overlook, overshadow or visually dominate neighbouring properties”, among other things. 8. The ‘Greater Cambridge Sustainable Design and Construction Supplementary Planning Document’ (which was adopted in January 2020) is also relevant, but it does not have the force of the statutory Development Plan. 9. The proposed rear extension would project into the rear garden of the property but would not be visible from public viewpoints and would not be obtrusive in the surroundings generally. It would preserve the character and appearance of the Conservation Area and would be acceptable in the context of planning policies that are intended to protect the historic environment. 10. The new extension would create a small courtyard at the rear of the existing house, where a side gate provides pedestrian access through the adjoining garden at number 17 and, beyond that, back to Hooper Street. This allows wheelie bins to be put out and brought in conveniently and the small new courtyard would accommodate the household bins (as shown on the submitted ground floor plan). The boundary fence on this side is less than two metres high but there is a small shed at the rear of number 17 and the proposed new extension at number 18 would not have a significant impact on the outlook or sense of enclosure for this neighbour. 11. The boundary at number 19 is also defined by a low fence, for the most part. This neighbouring house has a substantial shed or outbuilding in the rear garden and a glazed side extension that is built close to the boundary immediately behind the main part of the house. This is a very narrow extension, however, with a view down the garden, past the existing outbuilding, through the rear glass door, and I Appeal Decision: 6005170 3 am not persuaded that the outlook would be unduly harmed or that the new extension at number 18 would be overly intrusive. 12. In my view, therefore, the proposed new extension at number 18 would not cause unacceptable harm to the residential amenities of neighbours by being unduly overbearing or visually dominant, in its particular context. 13. Evidently, the appeal site lies within an established urban area, which is a “sustainable” location in planning terms, and the proposed extension would be a useful addition to the accommodation at 18 Hooper Street. The contribution that the appeal scheme would make to the provision of residential accommodation in the locality, even though it would be very limited, weighs in favour of the appeal. I have concluded that the project would not be in conflict with the Development Plan, in principle. 14. In short, I am persuaded that the scheme before me can properly be permitted and, although I have considered all the matters that have been raised in the representations, I have found nothing to cause me to alter my decision. 15. I have, however, also considered the need for conditions and I have concluded that standard conditions are necessary, to define the planning permission and to ensure that quality is maintained. 16. I have also considered the additional condition that has been suggested by the Council in the usual way (without prejudice to their main arguments in the appeal), proposing that the flat roof of the new extension should be designed as a “green biodiverse roof”. The proposed single storey extension is large enough for such a condition to be necessary and reasonable, to ensure that the development will make provision for water management and contribute meaningfully to the creation of habitats and valuable areas for biodiversity. Of course, the condition must also prevent the use of the flat roof as a terrace or sitting out area, since that would intrude on neighbours’ privacy. I have adopted the Council’s wording for this condition. Roger C. Shrimplin INSPECTOR Appeal Decision: 6005170 4 SCHEDULE OF CONDITIONS 1) The development hereby permitted shall begin not later than 3 years from the date of this decision. 2) The development hereby permitted shall be carried out in accordance with the following approved drawings: drawing number OS-01 (Existing Block and Location Plans); drawing number OS-02 (Proposed Block and Location Plan); drawing number SP-01 (Proposed Site Plan); drawing number 100 (Existing Plans / Elevations / Section); drawing number 200 (Proposed Plans / Elevations / Section). 3) The materials to be used in the construction of the external surfaces of the development hereby permitted shall match those used in the existing building. 4) Notwithstanding the approved plans, the flat roof of the single storey rear extension hereby approved shall be a green biodiverse roof. The green biodiverse roof shall be constructed and used in accordance with the details outlined below: a) planted / seeded with a predominant mix of wildflowers which shall contain no more than a maximum of 25% sedum planted on a sub-base being no less than 80 millimetres thick; b) with suitable access for maintenance; c) not used as an amenity or sitting out space and only used for essential maintenance, repair or escape in case of emergency. The green biodiverse roof shall be implemented in full prior to the use of the extension and shall be maintained in accordance with the Green Roof Organisation's (GRO) Green Roof Code (2021) or successor documents, unless otherwise agreed in writing by the Local Planning Authority.