Key steps

1. Acquire at least two maps of the city that showcase the location from different points in time, with at least a five-year difference.

2. Overlay the maps in a geographical information system (GIS) or by other means.

3. Compare building footprints manually or using computer software to detect changes.

4. Analyse the changed footprints to identify whether they indicate demolition or something else (like building extension).

5. Use additional data (for example Google Street View) to identify the key characteristics of demolished buildings, such as function and height/number of storeys.

6. Compare the key characteristics, including location, to new builds to identify opportunities for retention. This can include where similar buildings are demolished and built, or where buildings with potential for adaptive reuse are demolished.

7. Analyse existing buildings for key characteristics of demolished buildings to identify those at risk of future demolition.

Key steps

1. Get access to, or an extract from, the building register.

2. Make a simple descriptive statistical analysis of the demolished and built buildings, highlighting their quantities and key characteristics. 

3. Compare the key characteristics of the two stocks to identify similarities and differences in (for example) functions or sizes of demolished and new buildings.

4. If the register is geocodable, transfer the register information to GIS to analyse locations of demolished and new buildings to identify simultaneous occurrence in the same neighbourhoods or plots (like replacement).

5. Using the same approach, analyse the existing building stock for key characteristics of demolished buildings to identify buildings at risk of future demolition.

Key steps

1. Get access to, or an extract from, the city’s database on permits.

2. Search the database for the terms of interest (for example ‘demolition’, ‘deconstruction’, ‘replacement’ etc).

3. Analyse the identified permits for key characteristics of demolished buildings, such as location, function, floor area, building year etc.

Key steps

1. Establish where demolition has taken place in the city over a set period (outlined in method one above). 

2. Collate data on locational factors that could play a role in increasing or decreasing a building’s risk of being demolished. These could include: 

• transport access (proximity to motorways, public transport, airports etc)

• distance and quality of facilities and services

• historical and architectural characteristics

• safety

• land use

• land and property value

• planning zones and rezoning potential

• density of occupation

Geographically compare your demolition activity data with locational data to identify common trends. For example, that a high percentage of demolitions over the past five years took place in areas with poor transport links, or particular issues in a neighbourhood. 

Key steps 

1. Speak to colleagues or other planning professionals to understand how planning decisions around redevelopment and demolition are made. Decisions made by built environment stakeholders can greatly influence whether a building is transformed or demolished.

2. Conduct interviews and workshops with stakeholders to discuss the most influential factors. 

Questions could include:

• What are the key factors that guide decisions to demolish or refurbish?

• What do your short-term and long-term cost analyses include as assumptions?

• Is the impact on social value and communities included in your analyses? 

• What (or who?) might change a decision to demolish or retrofit? For example, tax incentives, legislative requirements, improved guidance, technological development, site context (location, building type). 

• Do you have any insights on how the decision to refurbish or demolish has come up in existing projects? Are there case studies? 

3. Market research into current and future built environment trends could help identify types of buildings or areas at risk of becoming obsolete now and in the future. Discussions with built environment stakeholders may shed light on these. Additionally, review reports and articles on relevant topics. 

Key steps 

1. Use building stock data to identify what kind of buildings are typically demolished in a city and what they are replaced with. See method one above.

2. Geographically compare demolition data with data on key external factors that may influence whether a building becomes obsolete and at risk of demolition. Identify common trends that may help predict where at-risk buildings are likely to be located in the future and the amount of floorspace that may be demolished. See method two above.

3. Hold discussions with built environment stakeholders to gain valuable insights about planning decisions, redevelopment and demolition that may not be publicly available. See method two above.

Recommendations

Urban planners and policy makers should use a circular perspective on all city development

Consider transformation possibilities when identifying land for development in the city. Overprovision of new space will vacate and drive premature demolition of already existing buildings with life cycle extension potential. For example, the list of ‘at-risk’ buildings could figure in these decisions.

• Tax empty buildings to prevent them becoming underused, vacant and falling into disrepair.

• Establish a lighter and quicker route to change the urban plan or deviate from a building’s stated function to help transform buildings temporarily, before the long- term plan is implemented.

• Design transformation projects for circularity ensuring transformed spaces can be adapted for another future use, or structures can be easily disassembled.

• Try to engage early on to create a common understanding between building permit and heritage protection departments and developers.

• Reserve funds for systematically developing life cycle extension in all branches of city administration.

Transforming a 1930s commercial site into student housing

Virtual Demonstrator

Overview 

Buildings on the commercial plot were originally developed for manufacturing, including production of timber, soda water and cast metal products.

Currently, the site houses businesses including auto repair shops, a night club, musicians’ studios, start-up companies and education services.

Threat of demolition

Industrial buildings account for the vast majority of demolished area in Denmark. Typically, a site like this is sold to a developer that will demolish it as far as possible so new housing can be built. The huge demand for housing in Denmark and soaring residential prices means the developer is likely to build at high density.

Transformation project

CIRCuIT partners in Copenhagen and local built environment stakeholders investigated how the site could be transformed into affordable student housing. Overall, the circular intervention’s lower material consumption resulted in a potential CO₂ saving of 23%.

Key findings

Public data has an important role in assessing transformation potential. A publicly available database made it possible to create static calculations and a 3D model of the building’s construction and layout to support the design process.

Gröninger HÖf Parkhaus – Giving new life to a heritage‑listed building

Physical Demonstrator

Overview 

This building is in a popular resort on the Baltic coast of Schleswig-Holstein, about 85km north-east of Hamburg city centre.

It was built as a one-storey car dealership in the mid-1950s and extended several times in the following years. In the early 2000s parts of the structure (sales areas) were heritage-listed because of the curved glass façade. In the last years before conversion, the building was briefly vacant during planning and project development.

Threat of demolition

Gaining heritage-listed status meant the building could never be demolished. However, analysis of demolished buildings in Hamburg showed it exhibits many characteristics typical of demolished buildings. This includes the commercial-industrial function, distant location and small, low-rise character. These buildings are often demolished without second thought to give way for denser and higher development – especially buildings without a heritage listing. A significant problem with buildings like this is how to use them and the land they stand on effectively while retaining spaces and components with preservation potential.

Transformation project

Transformation and extension of the existing heritage-listed building into a gym and vacation apartments was completed in 2020.

By strengthening the structure’s load-bearing capacity three extra levels for vacation apartments were made possible. This resulted in savings of 321 tonnes of materials, 186 tonnes of waste and 74 tonnes of CO₂ emissions. The cost of the circular intervention was 4.2% less than demolishing and building new.

Key findings

Early collaboration with heritage protection authorities was key for success. It helped precisely identify areas for preservation, alongside those that could be modified and by how much.

Increased density and a new future-oriented use was achieved through revised room layouts and structural strengthening to enable three new floors above the original building. Close collaboration with architects helped harmoniously integrate modern, high-quality features people would expect with the original heritage look.

Transforming 1970’s public rental housing to accommodate more people

Virtual Demonstrator

Overview 

This transformation covers two blocks of flats (one with three floors and one with five floors) in the Hakunila district of Vantaa. Both buildings were completed in similar Modernist style with precast concrete panels in 1979. The buildings have always been social rental housing.

Threat of demolition

There is no particular threat of demolition for the flats. However, there is pressure to demolish existing housing in the area as the urban population rises.

Social rental housing is particularly prone to demolition due to factors like:

• typically having only one institutional owner, which eases decision-making on demolition

• physical degradation of buildings or lacking necessary flat properties, e.g. in accessibility or demand on flat size

• socio-economic environment with precarious groups, neighbourhood image issues

• vacancy issues, mismatch of flat size with demand

• city’s policy targets for urban densification and social mix/gentrification and the potential value of the plot with a renewed urban plan featuring substantially increased building rights (in m²). 

Transformation project

Instead of demolition and replacement, urban densification targets were pursued through a retention and extension approach, with additional floors added on top of the existing buildings. Through consultation with the owner, it was decided there was no need to change the flat or room layouts. They serve the needs of renters well, as evidenced by the low vacancy rate. Instead, it was decided to balance out the flat-size offerings in the buildings with the help of additional floors to house smaller flats. The facades, building services and interiors of existing floors (including flats and shared facilities) were renovated as part of the overall transformation.

Additional floors were designed to be added on top of the existing buildings with the help of steel beams, running from cross-wall to cross-wall. This provides freedom for the placement and sizes of the new flats, as the new walls will not need to coincide with the underlying load-bearing walls.

The wooden load-bearing frame of the additional floors is lighter than concrete and helps to avoid the need to reinforce foundations, but also results in shorter spans. This fact, together with creating smaller flats, means that layouts may not be particularly adaptable in future.

Key findings 

If a city has a densification target, extending housing blocks with additional floors can be a technically, economically and environmentally viable alternative to demolition and new build.

The approach is particularly viable in social housing, as there is only one owner who can easily make the decision to transform. Because the building is non-profit, the project’s demonstrated cost saving is more relevant than the potential profit from demolition (a factor that can limit the interest of for-profit housing providers). As public actors, social housing companies could set an example for other types of housing providers.

Depending on the size and shape of the site and its location, a densification target may only be achievable if new buildings are constructed on the site as well as adding additional floors to existing buildings. The terrain and soil of the site may influence whether this is possible and what the cost implications will be.

Extending the life of a 1980s commercial shopping outlet

Virtual Demonstrator

Overview 

The subject of the transformation is a large commercial shopping outlet, which was completed in 1987 and functioned as a Do-It-Yourself store.

The structural scheme was created to be column-free through a structural steel spine truss along the length of the building. This is supported at an intermediate point by steel tension cables. The building is clad with sheet metal and sits on a concrete podium deck.

Threat of demolition

A developer recently acquired the outlet and surrounding land. The plan for the site is to build high-rise residential properties and retail outlets on it. This is because of the huge demand for residential properties in London. As a result, the large shopping outlet is at high risk of demolition.

Transformation project

In an attempt to save it, CIRCuIT partners in London explored options for retaining and transforming the whole building. The sectors these options covered included retail, multifunctional/cultural, healthcare, transport, industrial/manufacturing, agricultural, sport and research/educational.

After considering the different options and the potential environmental and economic benefits, the developer decided none of the transformation options were suitable.

However, dismantling and re-erecting the entire structural frame on another site was chosen as an alternative option.

This circular intervention (retaining the substructure, steel frame and roof) would save up to 1.2 million kg of CO₂ compared to a new building alternative.

Key findings 

This kind of project could potentially be replicated across other out-of-town retail units. This could result in a reduction in whole life carbon emissions of 400,000 tonnes of CO₂ across Greater London.

B. Public and private asset owners can identify the optimum cost and carbon
approach to projects by commissioning assessments of different degrees of retaining and transforming existing assets. 

Strategic: Public and private asset owners can improve projects’ costs and carbon profiles by commissioning early-stage assessments of different degrees of retention and transformation to meet future needs. This is rather than just comparing default demolition or a façade retention-only approach against minimal refurbishment of existing buildings.

Financial: In the demonstrator projects on which this case is based, life cycle costing found the total costs of optimal approaches to existing buildings result in savings of 7% and 26-41% compared to default new build or façade retention only. The savings range from €1m to €5.5m, indicating a strong case for investment in assessments.

Feasibility: Skills exist to implement assessments of various approaches to building retention. The benefits should be considered at the start of projects and consultants appointed on the basis of proven abilities and their willingness to interrogate the best use of existing assets.

Risk: Regulations might change during a development project. Setting out early on with evidence of the optimal approach to existing assets minimises the risk of developing a BAU approach and creating abortive work that’s non-compliant under new regulations.

Scalability: This approach would not work on sites where city planning allows significantly taller new buildings than can be achieved through retention and extension of existing buildings. Nevertheless, the demonstrator cases are widely applicable across many other sites and building types. While the Korso School project showed significant economic advantage in carrying out various levels of refurbishment, North Row was more marginal. In marginal projects, making the economic case for building retention may require new financial incentives such as (in a UK context) charging VAT equally on new build and refurbishment.

Related demonstrators: Demonstrator 19 – Korso School, Demonstrator 24 – North Row

D. Public and private asset owners can activate a neighbourhood and support new businesses by retaining existing assets for temporary use during long-term, phased regeneration projects.

Strategic: Public and private asset owners can activate a neighbourhood and support new businesses and job creation by assessing masterplans to identify existing assets to retain for temporary use during long-term, phased regeneration projects.

Financial: In the demonstrator project on which this case is based, construction costs for adapting and upgrading an existing building were 6% less than providing an equivalent new building. The projected return on investment over a fifteen-year temporary use period was enhanced by 8% compared to the new build alternative. Compared to a scenario in which the existing building is demolished, not replaced, and the land is rented out, the building retention option creates significantly higher net revenue, more jobs and a greater net total Gross Value Added.

Feasibility: Building retention to support temporary use is a familiar concept and skills exist to achieve it. The challenge is to recognise opportunities early on, assess their merit in terms of placemaking and social as well as economic value, and place sufficient weight on these benefits when briefing for design and phasing. Triple bottom line assessments should inform the approaches taken towards existing buildings.

Risk: Temporary uses can be seen as a risk for landowners in terms of safety and logistical reasons or delays in getting vacant possession when the site is due to be developed. A building or site will not always be suitable for temporary uses – for example if access blocks construction vehicles – but this can be considered in the early planning stages. Vacant possession can be ensured by establishing lease arrangements and maintaining clarity about the temporary use period.

Scalability: Large-scale redevelopment of industrial areas, such as the project that provided this demonstrator, are common in expanding urban areas where there is high demand for housing. With long redevelopment timeframes, there is good scope to treat existing buildings as assets that can provide income and social benefits through temporary use.

Related demonstrators: Demonstrator 23 – Block F

N. Private asset owners, investors and developers can gain recognition and achieve market differentiation by assessing whole life carbon when deciding between retrofit and demolition.

Strategic: Private asset owners, investors and developers should include results of whole life carbon assessments in strategic decision-making over retention and retrofit versus demolition and new build. This will help them meet changing legislation and public perception.

Financial: In the demonstrator projects on which this case is based, life cycle costing over a 50-year period found the total costs of retrofit scenarios to be 37%, 36%, 25% and 4% lower than new build.

Feasibility: There is growing capacity among consultants including access to software to enable whole life carbon assessments. In the demonstrator projects, the whole life carbon of retrofit scenarios was found to be 23%, 19% and 6% lower than those of new build. Giving the results of assessments sufficient weight in strategic decision-making, beyond meeting statutory minimum requirements, will be a matter of developers’ setting their own policies and targets.

Risk: Gaining recognition for transforming underused buildings and exploiting opportunities for creating new housing in existing assets minimises businesses’ exposure to the risk of demolition becoming an unacceptable approach in many contexts. Developing the capacity to work efficiently with existing assets builds businesses’ resilience to shifts in policy and taxation that incentivise retrofit over demolition and limit whole life carbon.

Scalability: There are few barriers to introducing whole life carbon assessments and taking them into account when deciding between demolition and new build. The demonstrator projects indicate economic and environmental benefits as well as reputational benefits in doing so. The ability to scale retrofit as a solution requires greater familiarity working with existing buildings across the construction value chain and innovation in surveying methods to de-risk and generate better information about existing buildings.

Related demonstrators: Demonstrator 13 – Godewind Park, Demonstrator 18 – 1930s commercial plot, Demonstrator 21 – Vantaa office building

Y. Citizens can form cooperatives and create new affordable homes and workspaces by identifying and transforming underused assets.

Strategic: Citizens can form cooperatives to work with municipalities to identify underused assets that are otherwise a blight on the urban landscape and at risk of demolition, and transform them into productive buildings.

Financial: In the demonstrator project on which this case is based, transformation of an underused multi-storey car park into housing resulted in a saving in demolition costs of around 15%. It also led to a total construction cost reduction of around 5%, compared to demolition and new build.

Feasibility: A key step for citizen-led cooperatives is to form relationships with city planners and collaborate in identifying underused assets suitable for transformation. The demonstrator project found that there is increasing appetite among cooperatives to invest in alternative residential-led mixed use developments.

Risk: Early investigation of existing structures is critical to ensure any hazardous materials or historic contamination can be remedied and the associated costs and risks are understood.

Scalability: The demonstrator focused on a multi-storey car park. Many cities are aiming to reduce car use and keep cars out of inner-city areas. This means reuse and transformation of car parks is one opportunity to scale creation of valuable living, social and commercial spaces in inner cities. In Hamburg, nearly 10,000 parking spaces in multi-storey car parks are expected to be suitable for transformation in the next twenty years. Municipalities can support cooperatives by systematically identifying these and other assets at risk of demolition to maximise the likelihood of their transformation and the social, environmental and economic benefits shown in this demonstrator.

Related demonstrator: Demonstrator 15 – Gröninger Hof Parkhaus