Retrofit conversations tend to focus on the building: its structure, envelope, services, energy use and carbon. These are essential considerations, but they capture only part of what retrofit can achieve. What if we also considered what a retrofit can do for the wider city around it? 

The street is one of the city’s most enduring forms of infrastructure. Buildings may come and go, but streets and squares persist, carrying routes and patterns of movement established generations ago. This is especially true of London, which still largely allows people to move through streets and courtyards with origins in the medieval city. 

In many places, however this inherited logic has been disrupted: routes have closed, ground floors privatised and connections severed. A closed route lengthens journeys; a privatised ground floor deadens the street edge; a severed connection isolates a building from its neighbours. Retrofit can reverse this, making a building both a better neighbour and a better-performing one: opening up a ground floor can support local businesses, while shade and planting can reduce demand for mechanical cooling. 

At Norton Folgate in Spitalfields, our regeneration of Elder Yard & Studios began by identifying the value of historic passageways closed long before the project. Reinstating these connections brought new activity to a previously under-utilised site at the edge of the City of London. At Park Tower Hotel in Knightsbridge, deep retrofit of Richard Seifert's 1970s hotel is repairing a public realm weakened by later extensions. A new two-storey podium replaces a hard edge with an active one, with a retail colonnade on William Street and new entrances on Lowndes Square. 

Here, the street remains outside the building. Elsewhere, we have explored a more complex relationship, where the street becomes part of the building itself. At the new London Museum, due to open in November, we developed a masterplan around a former market lane running between the 1960s Poultry Market and the Victorian General Market. Acting as the complex’s organising spine, the lane resolves circulation and logistics while creating a welcoming civic threshold. Naturally ventilated and glazed at both ends, it also helps moderate temperature and moisture across the galleries on either side, reducing reliance on mechanical systems. 

Central Saint Martins follows a similar principle. Here we created a 100-metre internal street through the Granary Building and the old marshalling yards, following the line of the freight tracks that once served the Victorian complex. The street draws daylight deep into the plan and places every discipline on a shared route. More than a decade on, its impact is organisational as well as spatial: shared workshops replaced departmental territories and, as former Head Jeremy Till observed, changed the culture of the college. By drawing the security line deep into the building, we also enabled restaurants, shops and public events to animate its edges, contributing to the regeneration of the wider King’s Cross area. 

Together these projects suggest a broader way of thinking about retrofit, beyond carbon metrics, funding cases and planning submissions focused within the site boundary. If retrofit is to contribute to a more sustainable and resilient London, we need to consider the street as part of the infrastructure being renewed. Sometimes that means reopening a lost route or repairing a damaged edge; sometimes blurring the boundary between outside and inside. In each case, the aim is to make an existing piece of city work harder: not simply to consume less energy, but to support more exchange, connection and life.