Preserving Heritage While Increasing Foundation Capacity

When a Grade II listed building in Bristol was earmarked for conversion into residential apartments, engineers identified a significant challenge beneath the structure. The existing foundations required increased load-bearing capacity to support the proposed development, but the weak made-ground soils and restrictions associated with the historic building ruled out traditional underpinning methods.

Mainmark was engaged to deliver a non-invasive foundation strengthening solution that would improve ground conditions, preserve the integrity of the listed structure and keep the development programme on track. Using Teretek® engineered resin injection, Mainmark successfully strengthened the foundation soils without excavation or disruption to the historic masonry.

The Challenge

The proposed apartment conversion required the building's foundation soils to achieve a design bearing capacity of 250 kN/m². Site investigations identified approximately three metres of weak made-ground sand beneath the existing shallow foundations, creating concerns around future structural performance and settlement.

Traditional concrete underpinning was considered impractical due to:

• Restricted site access.

• Extensive scaffolding surrounding the structure.

• The need to protect a Grade II listed asset.

• Programme and budget constraints associated with invasive works.

• The risk of disturbing historic masonry and foundations.

A faster, less disruptive alternative was required to strengthen the ground while preserving the building's heritage value.

The Solution

Mainmark utilised its proprietary Teretek® resin injection technology to improve the strength and stiffness of the soils beneath the foundations. The process involved injecting expanding engineered resin directly into the weak soil layers, compacting loose materials and increasing load-bearing capacity.

The compact equipment footprint allowed the team to work around existing scaffolding and construction activities without requiring excavation, heavy machinery or foundation replacement.

Key elements of the solution included:

• Targeted Teretek® resin injection beneath foundation zones.

• Treatment of weak made-ground soils to depths of 3 metres.

• Continuous monitoring of masonry movement using precision laser equipment.

• Dynamic Cone Penetrometer (DCP) testing before and after treatment.

• Verification that required foundation performance targets had been achieved.

Monitoring and Validation

Protecting the historic structure was a critical project requirement.

Mainmark implemented comprehensive monitoring throughout the works, including real-time laser monitoring of the building's masonry and pre- and post-treatment DCP testing. This enabled the team to validate soil strength gains and confirm that the required design bearing capacity of 250 kN/m² had been achieved.

The controlled, non-vibratory nature of the injection process ensured the listed building remained protected throughout remediation works.

The Outcome

The project was completed within a five-day programme, significantly faster than traditional underpinning approaches. Foundation soils were successfully strengthened to support the proposed apartment conversion while maintaining the integrity of the historic structure.

The solution delivered:

• Increased foundation bearing capacity.

• Improved ground conditions beneath existing foundations.

• Successful support of a multi-storey residential conversion.

• Protection of the Grade II listed masonry structure.

• Delivery within programme and budget constraints.

• No damage, cracking or disturbance to the historic asset.

Heritage Building Foundation Repair Without Underpinning

Historic and listed buildings often present unique engineering challenges. Traditional underpinning can be costly, disruptive and difficult to implement where access is restricted or heritage preservation is a priority.

Teretek® resin injection provides an effective alternative by strengthening soils beneath existing foundations without extensive excavation. This enables engineers and property developers to improve load-bearing capacity, reduce settlement risk and preserve valuable historic assets.

Project Benefits

Heritage Protection

The non-vibratory injection process preserved the structural integrity of the Grade II listed building and its historic masonry.

Rapid Delivery

Works were completed in just five days, helping maintain programme certainty for the development.

Minimal Site Disruption

Compact, hose-fed equipment enabled treatment within a constrained construction environment without heavy machinery.

Sustainable Foundation Improvement

Existing foundations were retained and strengthened rather than replaced, reducing material consumption and environmental impact.

Need Foundation Strengthening for a Listed or Historic Building?

Mainmark's Teretek® resin injection technology provides a fast, non-invasive solution for foundation strengthening, ground improvement and settlement remediation. Whether you're planning a heritage building conversion, addressing weak foundation soils or seeking an alternative to underpinning, our specialist team can deliver proven outcomes with minimal disruption.

Contact Mainmark today to discuss your project requirements.