Retrofitting starts below ground

Keeping an existing building in use for several decades means more than simply maintaining what is already there. As buildings are adapted for new uses, heavier equipment and more ambitious upgrades, the demands placed on them can change significantly. This makes understanding the condition of the whole asset increasingly important – including the ground supporting it.

Retrofitting is not just about improving energy performance. It’s changing what existing buildings are expected to do. Across the commercial property sector, warehouses are being upgraded to accommodate heavier automation systems, offices are being repurposed for changing patterns of workplace culture and industrial facilities are installing larger equipment to meet evolving operational demands.

At the same time, we’re seeing more designers extending buildings, adding mezzanine floors and introducing rooftop solar or green infrastructure to maximise the value of existing assets without rebuilding.

These interventions are carefully engineered above ground, but they can introduce new demands on foundations that were originally designed for a very different building. The challenge is not simply whether the structure can accommodate these changes, but whether the foundations and supporting ground can cope with the additional demands being placed on them.

Ground conditions are not static either. Changes in groundwater, nearby development, ageing drainage infrastructure and soil movement can alter how foundations behave, even when the building itself appears unchanged. This makes understanding ground conditions an important part of assessing whether an existing building can accommodate its proposed future use.

Climate resilience has become an established consideration in building design, with the industry responding to overheating, flooding and increasingly extreme weather. Yet the stability of the ground beneath existing buildings can receive considerably less attention.

That risk is already carrying a significant economic cost. The British Geological Survey (BGS) estimates that shrink–swell ground movement has cost the UK economy around £3 billion over the past decade, making it one of the most damaging geohazards.

With half of England declared in drought in July 2026, the impact of prolonged dry conditions is an increasingly important consideration for the built environment. For buildings founded on shrink-swell clay, like many in the south of England, changes in soil moisture can cause the ground to contract, increasing the potential for movement beneath foundations.

The need to consider these risks before building work begins is also being highlighted by the BGS. Anna Harrison, applied Quaternary scientist at BGS, says planners, property owners and developers can help limit future subsidence by “taking specialist advice before starting major building work… and ensuring the foundation designs of new constructions or extensions take into account the impact of climate change on shrinkable clays.”

For owners and occupiers, the consequences can extend well beyond the cost of repair. Ground movement can disrupt operations, delay refurbishment programmes and undermine investment made elsewhere in a building. This is why ground stability must be considered as part of the sector’s wider approach to climate resilience. If retrofit is intended to make buildings more adaptable and resilient, the ground on which they depend cannot be an afterthought.

Ground investigations have traditionally been triggered by visible defects. Cracking masonry, uneven floors or sticking doors can prompt surveys once movement has already begun to affect the building. By that point, the issue has become a reactive maintenance problem rather than a consideration that could have been incorporated into the refurbishment strategy.

That approach is increasingly difficult to justify as retrofit projects become more complex and the financial and environmental case for retaining buildings becomes stronger. Designers and developers already assess structural condition, building services and energy performance before committing to major refurbishment. Where there is potential for movement or changes in loading, understanding the condition of the ground should form part of that assessment too.

The stability of the ground beneath existing buildings can receive considerably less attention

The objective is not to suggest that every existing building requires ground remediation. It is to identify potential issues early enough for project teams to understand the implications and make informed decisions about the future of the asset.

Where intervention is required, modern ground engineering techniques can provide alternatives to traditional excavation and underpinning. Less invasive approaches can improve ground conditions with limited excavation, helping to reduce disruption to occupied buildings and maintain operational access while remedial work takes place.

For commercial assets, this distinction matters. A ground problem does not necessarily need to result in a major construction programme, prolonged closure or disruption to tenants and operations. And the value of being able to intervene with less disruption is already being demonstrated across critical infrastructure.

A warehouse fit-out project in Gloucester demonstrated how early intervention can support the adaptation of an existing building. During the installation of a new mezzanine floor, shallow voids measuring approximately 5-10mm were identified beneath the existing concrete slab at 13 proposed base-plate locations. Left untreated, the voids would have likely affected load transfer beneath the new structural supports. Traditional concrete breakout and reinstatement would have added time, dust, waste and disruption to the fit-out programme.

Instead, engineers used a targeted injection technique to fill the voids and restore continuous bearing support beneath the new mezzanine base plates, without removing the existing slab. The 65 injection points were treated by a two-person team during one working day, while the warehouse remained fully operational.

The project illustrates an important point for retrofitting. When existing buildings are being adapted for new uses or additional structural loads, ground-related issues do not need to derail the wider programme. Identifying them early creates more opportunity to select an appropriate intervention and incorporate it into the refurbishment works, rather than allowing a localised ground problem to become a larger construction issue.

The starting point for a more proactive approach is not necessarily extensive ground investigation on every refurbishment project. Instead, project teams should consider whether proposed changes could alter the demands placed on existing foundations, or whether there are signs that ground conditions may have changed since the building was constructed.

A change of use, additional loading, an extension or new rooftop can all provide reasons to revisit the relationship between the building and the ground beneath it. A history of cracking or uneven floors may also indicate that movement needs to be understood before further investment is made. Identifying these issues during the early stages of a project gives engineers more opportunity to assess the options available and incorporate any necessary work into the wider refurbishment programme.

Taking this approach also changes how ground remediation should be viewed within a refurbishment project. Rather than being an unexpected cost that appears once a defect has developed, addressing ground conditions early can become part of the wider strategy for protecting an asset’s value. Understanding the available options alongside planned structural, energy or building services upgrades can help project teams coordinate works, manage disruption and make better decisions about the future of the building.

The next generation of retrofit projects will need to consider more than what can be upgraded, replaced or added above ground. If existing buildings are expected to deliver value for decades to come, their future performance needs to be considered from the ground up.