Mansard roof extensions London
Mansard roof extensions are the most cost effective way to maximise the floor area of your house or flat when compared to adding the same floor area with a rear or side extension. Mansard roofs are a widespread and traditional method of adding an extra storey to the top of a Georgian, Victorian or Edwardian building. Named after a French architect, Francois Mansart, the mansard roof comprises a sloping roof clad in slate or tiles, set back behind a parapet, with dormer or attic windows, which either project from or are recessed into the slope. It emerged in the eighteenth century in Britain, when it was also referred to as a kirb roof. It allows extra accommodation at roof level, partially hidden behind a parapet wall, without having a great impact on the appearance of the façade below. Below we have selected some projects to lend architectural inspiration and design ideas for your Mansard roof extension.
Start considering how you would like to use your new space, and how it will interact with the rest of your home. It’s important that the new extension blends with the rest of the building and is easily accessible, so when considering the staircase think about its long-term use as much as its style. During the design development stage we will get to explore lots of ideas but you can start the process now by considering answers to questions as such:
“Space permitting, how about adding an en-suite, a walk-in wardrobe, or even a coffee area in front of a Juliet balcony?” “What do we think about rooflights in the bedroom? They bring more light into the room but how about the rain ticking on the glass; is it charming or just plain annoying?” “Planning permitting, how about we sacrifice some of the internal floor area to create a small balcony with doors opening up to it directly from our new (master-) bedroom?”
There are two main types of mansard roofs:
Modern | Modern roof extensions often have a flat roof profile at the top, with a gentle slope to the rear. There are several crucial elements to the correct appearance of a mansard roof, namely materials, slope of the roof, proportion of the dormer windows and extension of the party walls and chimneys. Such roof extensions always require planning permission from your local authority.
GOAStudio | London residential architecture and interior design is an award-winning practice, specialising in architectural services for residential projects across London.
Our architectural team aims to provide a friendly and professional service. Our approach is based on carefully considering the particular aspects of each scheme before coming up with a creative way for our clients to instil their unique stamp on what we do and how we do it. Royal Institute of British Architects (RIBA) and Architects Registration Board (ARB).
Awards + Achievements

New planning approval | Residential development and conversion to flats Hammersmith Fulham W6
Planning approval for a residential development and conversion to flats Hammersmith Fulham W6 - Erection of an additional floor at roof level; erection of front extensions at ground, first, second and third floor levels, and conversion of the ground floor garage into...
New planning approval | Residential development and conversion to flats Islington N7
Planning approval for residential development and conversion to flats Islington N7 - Single storey half-width upper floor rear extension, a new roof terrace, a new mansard roof extension, and internal alterations to create an additional 1bed flat over the upper ground...
New planning approval | Alterations and extension to a house in conservation area Harrow HA5
Planning approval conservation area Harrow HA5 - Addition of a new front porch, enclosing an existing veranda area at the rear to create a new guest room, and minor external alterations including to windows and doors. We are happy to announce that we obtained a new...