Look up to look forward: the benefits of vertical extensions
Brook House, credit: Chris Dalton
Article posted on: 3 March 2025
In today's rapidly evolving urban landscapes, the pursuit of new development often leads to a pivotal question: where to build? Satpal Sagoo shares his thoughts on a sustainable solution.
The government has committed to ambitious housebuilding targets, with plans to build homes on neglected brownfield sites top of the agenda. In fact, £68 million from the Brownfield Land Release Fund will enable 58 councils to unlock disused sites and enable 5,200 homes to be built across the country. The government’s determination to build more homes is a welcome move. That said, there is only so much brownfield land available that is ripe for development. So, where does this leave commercial schemes – the office blocks, hotels or industrial units that create new job opportunities and catalyse economic growth?
A balance must always be struck between residential and commercial development when it comes to creating thriving communities where people live and work. What, then, is the answer to this quandary?
Vertical extensions – adding new floors atop existing structures – can be a sustainable and efficient solution to this dilemma.
By building upwards, we can conserve land for housebuilding, optimise resources, utilise existing infrastructure and contribute to a more sustainable future.
The benefits of vertical extensions
Opting for vertical growth over horizontal sprawl offers several environmental and economic benefits - many of which I covered in a previous blog.
Chiefly, vertical extensions can enable greater land conservation: allowing for increased capacity without consuming additional ground space, preserving land for housebuilding or green spaces. Expanding upwards also uses existing infrastructure, such as foundations and utilities, more efficiently. This approach minimises the need for new roads, sewage systems, and other utilities that horizontal expansions would require.
It’s also a more sustainable choice: taller buildings can harness natural light and ventilation more effectively, reducing dependence on energy-intensive artificial lighting and climate control systems. This can lower energy consumption and minimise a building's carbon footprint, helping to achieve ESG targets in the process.
What’s more, vertical extensions often prove more cost-effective than horizontal expansions, as they eliminate the expenses associated with land acquisition and extensive groundwork, especially when it comes to brownfield sites.
Cases in point: our vertical extension expertise
Located in London's Westminster district, this transformative retrofit development saw the refurbishment of The Dacre, an existing 1970s reinforced concrete office block, to create an impressive eight-storey office building. Our civil and structural engineering design teams planned and oversaw the strategic demolition of the upper storeys, followed by a vertical extension.
The project elevated the structure to eight storeys, creating a high-quality commercial development in a prime central London location, while saving the existing building from demolition.
Situated on a prominent corner position in a Victoria conservation area, modern, vibrant workspaces now occupy seven floors of The Dacre. With 20,560 sq. ft. of contemporary office accommodation in total, the extended building is designed to foster a sense of collaboration.
Sustainability informed every aspect of the extension to minimise the building’s environmental impact. From cycle stores to shower facilities, every detail is thoughtfully curated to promote a greener, healthier way of working.
On the eighth floor, a communal roof terrace offers panoramic views towards St James’s Park, a key feature for this stunning building. The ground floor houses restaurant and retail businesses, providing much-needed jobs in the local area.
The Dacre was shortlisted for the Architects’ Journal Retrofit & Reuse: Saved From Demolition Award 2024.
The Dacre
Over on Shepherds Bush Road, Hammersmith, we refurbished Brook House, a 1960s office block, including a vertical extension, to deliver a new £16m hotel scheme for Legal & General, which is operated by Premier Inn.
The existing structure is a reinforced concrete frame with beam and clay pot floors. To add two storeys to the existing four-storey structure, we undertook extensive trial pitting and below-ground site investigation works to justify the proposed re-use of the existing foundations.
Both of these projects showcase how the sky is the limit when bringing to life ambitions to breathe new life into existing structures, rather than pursuing costlier, time- and resource-intensive demolition and new-build options.
Overcoming the challenges of building upwards
While the benefits are clear, vertical extensions like The Dacre and Brook House present unique structural engineering challenges.
In close collaboration with architects, engineers, and stakeholders, we can devise cost-effective and safe solutions to these challenges.
Before we get going, our dedicated civil and structural engineering design teams work with our project partners to conduct thorough assessments of the existing structures to determine the capacity to support additional floors. This may throw up urgent structural work that needs to be completed. For example, existing foundations may require strengthening to bear the added weight of new storeys. We also ensure that the client’s plans for an extended structure meets all relevant Building Codes, regulations and standards to create a safe, compliant build. It’s also key to identify the new and old structural elements that need to be connected to maintain the building's overall stability.
Embracing a vertical future
As urban populations grow and the demand for space increases, vertical extensions offer great scope for redevelopment.
By expanding upwards, we can create thoughtful, sustainable, efficient, and vibrant urban environments that meet today’s needs while preserving resources for future generations.
