Project type
Sketchy renders of the streetcape and demonstrating how the mansard extension will fit nicely on the busy high street in Lewisham, London
Two-bedroom apartment
View of the streetscape from the ground demonstrating the different levels of the existing building and mansard extension alongside the modern glass balustrades
Unique mansard extension with beautiful rust colour and arch windows
Aerial side photo-realistic renders of the extension with it's beautiful rust coloured panels and mixture of sleek straight-edged lines and arched windows
Airy reading nook with floral muted wallpaper pattern and feather winged chandelier
High ceilinged liviing with with wall-mounted tv and storage console with bright large arched windows and skylight
Modern and sleek kitchen with a center dining table and thick gold accents in the chair legs and light chandelier
Close up of the warm rich brown dining table, with a feathered centered piece in a black marble vase
Two-bedroom apartmen
Two-bedroom apartmen

Bold yet respectful upward extension to create a new apartment in a conservation area


Deptford High Street SE8

Local Authority

Lewisham Council

Plot Type

Conservation Area

Project Type



Two-bedroom apartment

Services by Urbanist Architecture

Project Architect, Delivery Architect, Planning Consultant, Lead Consultant


Mint Structures, TPA


Can you build upwards in a conservation area?

The answer is sometimes. There are definitely both developers and homeowners who will underestimate or misunderstand the workings of heritage protections and submit doomed applications for all kinds of rooftop developments.

But that doesn’t mean you can’t sometimes make careful additions to buildings in conservation areas. In this case, the plan was to create a new flat above a corner building on a busy high street. It’s four minutes from a train station, six minutes from the street market and the library and seconds away from an incredible range of shops. It’s a short walk to schools, universities and dozens of historic buildings. In short, it’s exactly the kind of place where we should be building new homes, and even more so if can be done with a subtle addition to an existing building.

But could we create something that would be considered acceptable within the conservation area restrictions?

Before & After

Existing roof plan which was very large and flat and hence had plenty of potential to develop a two-bedroom flat


One thing was clear – there was plenty of room on the roof of the building for a two-bedroom flat. And there was already a brick structure housing a doorway to the stairs on the roof, and we wouldn’t be going much higher than that.

So the problem wasn’t about how to create a good home in an excellent place to live. It was about whether we could design the outside of it to look like it fit into the conservation area, and whether the council would accept it would be a suitable neighbour for a listed building.

To achieve that, we went for a smart metal covering for the mansard, something to give the roof a timeless quality, and one we knew would age well, which is very important for this kind of project. The balcony balustrade was glazed, so that there wouldn’t be anything obtrusive on the edge of the roof.

Had we done enough? The council, unfortunately, didn’t think so and refused the application. However, we appealed and the planning inspector thought very differently. He felt the design was “sensitive” to its context and that “The proposed architectural detailing including the round topped dormer windows and mix of vertical and pitched elevations would be sympathetic to the original features of the building and match similar design aspects in the surrounding area.” Due to that, he gave the mansard planning consent.

As we said at the start, building upwards in a conservation area is not easy. But sometimes, with the right design, it can be done.

Unique mansard extension with beautiful rust colour and arch windows

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