Traditional underpinning is a common method used to treat subsidence and foundation issues, but it can be a slow and costly process. Critically, it is often incompatible with listed building legislation. Any demolition, alteration, or extension work on a listed building requires listed building consent. Consent is also needed for any other types of work that will affect the character of a building with special architectural or historic interest. As a result, traditional underpinning methods may not be a suitable option.

Resin injection

Modern, non-invasive alternatives such as resin injection, is often faster, safer, and far less disruptive. Mainmark UK’s Teretek® solution involves injecting resin into voids through small holes beneath the foundations. The engineered resin then expands and makes the soil more compact, fills voids, and stabilises foundations.

Interestingly, consent is not often required for stabilisation works only. So, it can be a compliant option under heritage building frameworks. Resin injection offers several benefits:

• Fast delivery – work is typically completed in days not weeks.

• No excavation or heavy machinery required.

• Allows homes and public sites (such as visitor attractions, churches etc) to remain occupied, minimising disruption.

In 2023, Mainmark UK used Teretek® resin injection to address subsidence in sixteen Grade II listed post-war social housing bungalows owned by Birmingham City Council. Problematic ground conditions such as variable concrete slab thicknesses and a high-water table meant that traditional underpinning methods would be unsuitable. Resin allowed for the rapid strengthening of foundations through minimally invasive injections with very little disruption to residents and heritage buildings.

The same method was applied to combat subsidence beneath a Grade II-listed 1935 former bank building in Chester. Following deep-probe investigations, it was discovered that 18–20m of poorly consolidated quarry-infill soil sat below the foundation. This contributed to the ongoing downward movement. Resin injection was selected as traditional underpinning would be highly disruptive due to the location and depth. A noticeable lift was achieved in some areas in just 14 days.

Additional ground solutions

Resin injection is just one method for ground repair. Where resin isn’t suitable, complementary solutions such as screw piling and tree root barriers, can be used to address the foundation issues.

Screw piling

Screw piling, sometimes referred to as helical piling, uses high-strength steel shafts with helical plates which are screwed into the ground using specialised hydraulic equipment. Screw piling is ideal for stabilising structures on clay soils with a high plasticity index, where the ground is prone to significant shrink–swell movement. In addition to being faster than traditional methods, screw piling:

• Creates less noise

• Less site disturbance

• Requires less curing time

Tree root barriers

Trees near heritage properties often cause ground shrinkage, particularly in clay soils. Trees on heritage sites are legally protected by either a Tree Preservation Order (TPO) or by being in a Conservation Area so cannot be removed without permission. Additionally, the removal of trees can have a negative impact on the beauty and biodiversity of the surrounding landscape.

Utilising a vertical, copper-infused geotextile root barrier system can encourage root growth away from susceptible areas or provide a boundary around a tree to prevent its roots from branching out too far. The system releases copper ions into the soil that signals the roots to change direction and avoid penetrating the barrier.

Why choose Mainmark?

Mainmark UK’s non-invasive solutions enable rapid stabilisation with minimal disruption, allowing occupants to stay on the premises and public sites to remain open. Minimal equipment is needed on site, which makes resin injection ideal for urban areas or sites with limited access. Less equipment means less transport is required, resulting in a reduction of waste and carbon emissions compared to traditional methods. Learn how Mainmark UK is challenging conventional underpinning.

Dealing with subsidence and foundation issues on heritage buildings require innovative engineering approaches that sensitively address structural challenges. Mainmark UK’s advanced resin injection and complementary solutions like screw piling and tree root barriers offer a fast, non-invasive, and sustainable alternative to traditional underpinning. Not only do these methods stabilise foundations effectively, but they also minimise disruption, reduce waste, and often avoid the need for listed building consent.

If you need advice on dealing with subsidence on a heritage building, contact us today to find the best solution for you.