Sustainable housing provision: A case for the vertical extension of existing buildings

Since leaving the Grantham Centre, Dr Charles Gillott has stayed at the University of Sheffield and works as a Research Associate on a project titled ‘Multi-scale, circular economic potential of non-residential building stock’.

As a Grantham Scholar, Charles researched the potential for the vertical extension of buildings to make the construction industry more sustainable. 


Charles is a Civil Engineering graduate who completed his master’s with the department of Civil and Structural Engineering in 2019. As part of this, his final year research project began to explore the potential of sustainable housing provision through the vertical extension of existing buildings; a theme which continues throughout his PhD.

Charles’ wider research interests are centred on the circularity of material flows within the built environment and ensuring sustainable development through whole-building adaptation and re-use.


Rising house prices mean that, in September 2019, the average cost of a ‘first-time’ home in the UK reached almost £200,000 (ONS, 2019). This is the result of a historic under-supply of affordable residential accommodation, something which has also contributed to the near-record levels of homelessness currently observed in the UK.

An ever-growing demand and amassed deficit of over 4.8-million homes now means that, in order to meet the 15-year target set by the current government, a total of 380,000 new homes must be built each year (Wilcox et al., 2018). Considering that just over half of this number were completed in the year proceeding June 2019 (Ministry of Housing, Communities and Local Government, 2019), this represents a formidable task for the UK construction industry. 

As well as practical issues surrounding the construction of such large quantities of residential accommodation, additional challenges arise from the UK’s commitment to the Paris accord and the resulting legal requirement for the construction industry to reach net zero emissions by 2050. This pertains both operational and embodied carbon, dictating that potential solutions to the housing crisis must provide sustainable, energy efficient and cost effective residential accommodation through the use of reduced and/or low-carbon materials.

The Role of Vertical Extension

One way in which this may be achieved is through the adaptation of existing infrastructure. This serves to curtail the ongoing cycle of demolition and reconstruction through the re-use of whole buildings; improving energy and material efficiency via a significantly less energy-intensive construction process.

Of the suite of potential adaptive strategies which may be employed, the vertical extension of existing structures has notable additional benefits. These typically result from the fact that it serves to yield new usable floor space rather than simply renovating and/or repurposing existing space; something which is of particular importance when considering its use in the provision of large quantities of residential accommodation

Research Methodology

Due to the fact vertical extension remains within its infancy, the primary factors inhibiting its widespread adoption relate to uncertainty surrounding its safety and viability, as well as the amount of residential accommodation it is able to yield. This work therefore aims to increase understanding of the potential of vertical extension as a means of future sustainable development. 

Initially this will focus upon structural considerations; with the UK building stock being analysed to identify typologies with particular suitability for future vertical extension. A simplified framework of assessment for the rapid identification of reserve structural capacity within such structures will then be developed, and its validity ensured through a suite of case-study structural analyses.

The scope of Charles’ work also extends to consider stakeholder perceptions of vertical extension as a viable construction method; uncovering potential enablers of, and challenges to, the widespread adoption of this approach. The most pertinent technical, cultural, and regulatory considerations identified as part of this research will also be used to inform subsequent work. This will be in the form of a multi-scale assessment, whereby the number of residential units which may be obtained through vertical extension will be determined at the single-building, city and regional scale.


Charles has been working with Grantham Scholar Will Mihkelson and other University of Sheffield experts to develop a tool that encourages those involved in the design and construction of buildings to engage with the circular economy and build more sustainably. Find out more about Regenerate.


Charles Gillott, Buick Davison & Danielle Densley Tingley (2022) Drivers, barriers and enablers: construction sector views on vertical extensions, Building Research & Information, DOI: 10.1080/09613218.2022.2087173

Further publications are detailed here.

Charles Gillott in the news

Two storey extensions could help housing crisis and reduce carbon emissions. Charles led a study on two storey extensions to buildings. It found that these extensions could create 175,000 houses in Sheffield alone. Plus if rolled out across the UK they could reduce carbon emissions and help ease the housing crisis. This study was covered in various media, including the Yorkshire Post and the BBC.

Extensions on existing properties could create 175,000 new homes in Sheffield, according to university research. The Yorkshire Post covered Charles’ study on two storey extensions.

Sheffield university academics argue more buildings should be renovated to aid post Covid-19 recovery. Sheffield newspaper The Star featured a story on the Regenerate tool.

Charles Gillott: outreach

Levelling Up White Paper

Levelling Up White Paper: What the experts say. In Feb 2022 the government released it’s white paper on levelling up the UK. Experts from across TUoS, including Charles, explained what the proposals would mean.


In 2021, Charles and 6 other Grantham Scholars went to COP26 as official observers for the University of Sheffield. Before COP we spoke to each of them about their hopes and fears for this pivotal event. During COP Charles was interviewed by the Sheffield Telegraph. Read: Sheffield student will attend inner ‘Blue Zone’ at COP26 climate summit.

While at COP26, Charles wrote about a sustainable built environment for The Conversation. Read: We have reusable cups, bags and bottles: so why are our buildings still single use?

Blogs and articles

Charles Gillott on Institution of Structural Engineers’ sustainability map. Charles’ work on vertical extension included in the Institution of Structural Engineers’ Sustainability Resource Map.

8 vertical extensions you should know about. Charles outlines different types of vertical extension in this blog for The Institution for Structural Engineers.

Interdisciplinary Forum on Innovative Housing Solutions. In 2021, Charlies and fellow Grantham Scholar Philippa Hughes hosted a forum on innovative housing solutions. They both research housing, but Philippa is based in social sciences and Charles is engineering. In this blog, they reflect on what they learned through the forum and from one another.

Sustainability webinars 2021

Charles and other Grantham Scholars organised a webinar about housing as part of our public engagement work in 2021. For this event, experts from Nation Wide and community led housing projects discussed innovation in housing supply. Now you can watch this webinar on our YouTube channel.

Watch How can we enable sustainable innovation in the UK housing supply? by clicking the video below.

Social media and further information

You can find out more about Charles Gillott’s research on his Research Profile

Or connect with him on LinkedIn

And he’s on Twitter


Dr Danielle Densley Tingley

Department of Civil and Structural Engineering


Prof. Buick Davison

Department of Civil and Structural Engineering