Residential subsidence case study
Challenge
Recurring bay window subsidence caused by clay shrinkage threatened structural stability, recent repairs and homeowner confidence in a densely built London street.
Solution
Geobear delivered rapid non-invasive ground improvement beneath foundations, stabilising shrinkable clay and restoring confidence without disruptive excavation or underpinning.
Typical installation
Treatment locations
Maximum treatment
A homeowner in London began noticing widening cracks around the front bay window following an exceptionally hot, dry summer. Although the bay had previously been rebuilt, new movement had developed externally around the brick piers and internally around windows, ceilings and walls. Floors had also become noticeably uneven.
A structural assessment concluded that the movement was consistent with seasonal shrinkage of highly plastic London Clay beneath inadequate foundations. Geological information and local ground conditions confirmed the presence of London Clay overlain by granular superficial deposits, while nearby vegetation and seasonal moisture changes were identified as contributing factors. The structural engineer recommended ground improvement beneath the affected foundations rather than traditional underpinning.
Before any stabilisation works commenced, drainage was investigated to ensure no defects would compromise the treatment area. A failed rainwater drain serving the front of the property was identified and appropriate enabling works were completed prior to injection.
The front bay was founded within shrinkable clay soils that had experienced significant seasonal moisture loss during prolonged dry weather. As the clay contracted, differential settlement caused cracking around the bay window and adjoining masonry together with sloping internal floors.
Although the bay had been rebuilt previously, the foundations had not been designed to accommodate the challenging ground conditions. Without improving the supporting ground, movement continued despite the earlier structural repairs.
Traditional underpinning would have required extensive excavation immediately adjacent to neighbouring properties and boundary walls, creating prolonged disruption, significant excavation and concerns for adjoining homeowners.
client quote
Chris Nicolson
Geobear designed a bespoke clay shrinkage solution focused solely beneath the affected front bay foundations. Treatment was delivered through multiple injection locations positioned externally around the bay.
The specialist geopolymer material was installed in stages to multiple vertical depths of up to approximately 2.3 metres, creating a denser and more stable bearing layer beneath the existing foundations while minimising disturbance to the surrounding property.
Prior to treatment:
The entire stabilisation was completed in a single visit without excavation, heavy plant or the need for the homeowner to vacate the property.
The ground beneath the bay window was successfully stabilised, eliminating the need for disruptive underpinning.
Following treatment, the homeowner reported:
The works were completed with minimal disruption and are supported by Geobear's long-term residential guarantee.
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