Appeal 3273310

The appeal is allowed and planning permission is granted for the extension of existing mansard roof to the rear to provide acoustic screening for 7 No Air Conditioning Units with existing plant area to be relocated from the rear garden at ground floor level to roof level at the rear of the property at [site address] in accordance with the terms of the application, [name]/20/00896, dated 11 February 2020, subject to the following

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: PJ051/D/PL/103; PJ051/D/PL/101; and PJ051/D/PL/102.

Noise emitted by all building services plant and vents shall not exceed a level 10dBA below the existing lowest LA90(10min) background noise level at any time when the plant is operating, and where the source is tonal it shall not exceed a level 15dBA below. The noise emitted shall be measured or predicted at 1.0m from the facade of the nearest residential premises or at 1.2m above any adjacent residential garden, terrace, balcony or patio. The plant shall be maintained thereafter so that they operate within these limitations for the duration of the development.

The plant shall not operate unless it is supported on adequate proprietary anti-vibration mounts to prevent the structural transmission of vibration and regenerated noise within adjacent or adjoining premises, and these shall be so maintained thereafter.

All work and work of making good shall be finished to match the existing exterior of the building in respect of materials, colour, texture, profile and, in the case of brickwork, facebond and pointing, and shall be so maintained.

No development shall commence until a Code of [name] and Site Construction Management Plan (SCMP) for the development has been submitted to and approved in writing by the local planning authority. The development shall be carried out in accordance with the approved SCMP.

The main issue is the effects of the proposed development on the living conditions of nearby residential properties in relation to noise.

The proposed development comprising the construction of a mansard roof over the existing flat roof would extend the present mansard to the rear of the appeal property and would house air conditioning and ventilation equipment. The Council raise no objection to the design of the extension and do not consider it would harm the character or appearance of the Brompton Conservation Area. I have no reason to disagree with the Council’s assessment in this regard and I am satisfied that my duties under section 72 of the Planning (Listed Building and Conservation Areas) Act have been discharged.

Presently, the existing plant installation is located in the shared garden space between the appeal property and [address]. I was able to observe and hear the existing plant in operation during my site visit. In rehousing up to 7 pieces of equipment, the roof of the mansard would be left open through louvred panels to allow ventilation. Internally, the structure would be acoustically lined with the equipment mounted on anti-vibration mounts to assist in avoidance of structure-born noise.

A noise report1 accompanies the appeal proposal, which followed testing of noise levels at the two closest receptors, namely a rear window to the rear of [address], which faces the garden and the top roof skylight of [address] some 3metres and 7metres, respectively from the proposed plant room within the mansard extension. The report concludes that the proposal would meet the requirements of the Council’s Supplementary Planning Document on noise2 and comfortably meet the most stringent recommendations of BS 8233:20143 subject to recommended mitigation, including additional measures of enclosure.

Accordingly, the proposal would comply with policies CL5 and CE6 of the Royal Borough of Kensington and Chelsea Local Plan (2019), which amongst other things seek to ensure that new developments provide good living conditions for occupants of existing and neighbouring properties and where necessary mitigate and protect occupiers against sources of noise.

A number of conditions have been suggested by the Council and have been assessed and amended against the guidance contained in the Government’s 1 KP Acoustics Planning Compliance Review Report 19953.PCR.01 [name] dated 8 December 2020 2 Noise Supplementary Planning Document May 2009 3 [name] 8233:2014 ‘Guidance on sound insulation and noise reduction for buildings’ Planning Practice Guidance. In addition to the standard time period for commencement of development, a condition is included that sets out the approved drawings to ensure clarity. I have also included conditions that seek to control noise levels and vibration so that the living conditions of neighbours may be protected. A condition is included requiring the use of appropriate external materials. Finally given the tight configuration of dwellinghouses within this mews development, a condition is imposed requiring the submission and approval of a construction management plan together with its implementation.

For the above reasons, I conclude that the appeal should succeed.