Conversion of Penthouse roof - Grove & Company
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Conversion of Penthouse roof

About This Project

In 2000 we were approached by the owner of a penthouse in Chelsea whose 5th floor accommodation lay below a flat roof which occupied the footprint of the entire apartment building. The Client was seeking assistance as to whether he could introduce a stair into his apartment to access the roof which he wished to convert to a roof garden for his sole occupation and use.


Our first task was to obtain planning consent and the main issue was the kind of railings the Local Authority would permit to guard the perimeter of the roof so it could be accessed safely.


In our view iron railings would not blend with the architecture of the block so we opted for a scheme of glass panels secured between stainless steel posts. This was considered an unsatisfactory solution by the Council as in their opinion the balustrade would not appear transparent as we envisaged and they held the view that it would actually reflect the light.

We then devised a different strategy: the top floor of the building was a slate covered mansard with dormer windows so we produced a design solution whereby we would extend the mansard a further storey and this would achieve a sunken roof garden which could not be seen from neighbouring properties nor would it give any opportunity for people using the roof terrace to overlook adjacent buildings.

The back of the false roofs we constructed was fitted with powder coated aluminium louvres which housed services and a/c and additionally provided storage for barbecues and garden furniture.

In terms of connecting the roof terrace with the apartment, following receipt of structural advice, we formed an aperture in the roof, below which we installed an Oak helical stair. To protect the apartment from the elements the stair at roof level finished in a straight flight which took you into a glazed box with French windows giving access to the exterior.

As part of the overall scheme we also decked the roof with decorative tiles and introduced a water sculpture.

Twelve years later we were approached by the same Client who it transpired still lived in the apartment and this time he wanted to cover-over half the length of the roof terrace with glass so the space would be integrated into his apartment.

Once again, we approached the planners to seek permission for the construction of the glazed enclosure. On this occasion the Council considered that the glazed enclosure would cause night-time light pollution and therefore would be unacceptable.

Following further research, we returned to the Council with an alternative scheme using “Smart-Glass” which remains clear until an electric current is passed through it at which time it turns cloudy. The scheme offered to the Council incorporated a daylight sensor which prevented the glazing becoming clear during the hours of darkness. This scheme was accepted by the planners and consequently work commenced on site with a specialist glazing firm as main contractor.


The project took six months to complete and the glazed structure cost £200k plus VAT.

Design, Principal Designer, Project Management, Quantity Surveying