15 Mansfield Street

The Brief

15 Mansfield Street is a Grade II Listed building located in a predominantly residential street in the heart of the Marylebone conservation area. Our client purchased the property – which had formerly been used as an office by the Royal College of Midwives – when it was in a fairly dilapidated state and had an EPC D rating. The brief was therefore to refurbish, extend and upgrade the space, creating commercial office facilities that could be single or multi-let.

The client was targeting premium tenants and therefore everything was focused on delivering exceptional quality. An interior designer was engaged to work alongside the architect, and high-specification “plug-in-and-play” AV/IT facilities were added to the brief. A key component of the design was also to sensitively retain and enhance the building’s 18th century period features during the upgrade.


UK Real Estate


London W1


9,117 ft²


  • Office - Remodelling & Refurbishment


  • Cost Consultancy
  • Employer's Agent

The Challenge

There were a number of structural discoveries on site during the early part of the scheme that contributed to cost and programme challenges, and therefore the design had to be adapted in collaboration with the whole team. Our cost consultants worked very hard to represent the client’s best interests throughout this process to ensure an acceptable cost and programme outcome was achieved.

All alterations required Listed Building consent. After initial resistance from the heritage officer, we were successful in getting approval for new double-glazed sash windows to be installed into the building’s original frames, thus improving energy efficiency and enabling an EPC B rating to be achieved without compromising the streetscape. Neighbourly matters were also an issue, and our team liaised closely with the appointed party-wall surveyor to keep things moving.

The Outcome

The completed project entailed a full strip back of the existing building, structural alterations to the core, circulation areas and stairwell alongside the demolition of the existing roof in order to add a mansard roof-extension. This new roof floor was designed very much in keeping with the traditional style of the original building, with the space then earmarked to be marketed as an executive office suite.

The refurbished internal areas have been completed to a very high standard, with timber floors, wooden paneling and lime-washed walls enhancing the heritage look and feel. The scheme was delivered with the option that the client’s company would keep two of the floors. At the client’s request therefore, these floors were fitted out to an even higher specification, with artists employed to add bespoke decorative features.

Increase in net lettable area
0 ft²
Programme duration
0 months
Cost per ft²
£61 0

Other Projects We’ve Completed Include

The Gilbert & One Lackington

Michael Faraday House

New Hibernia House