Challenge
A failed drain saturated and washed away supporting fill beneath the property's raft foundation, causing differential settlement, extensive internal and external cracking, uneven floors and movement where the extension joined the house.
Solution
Geobear injected expanding geopolymer through 15 strategically positioned points approximately two metres below the foundations, strengthening weakened ground, filling voids and permanently stabilising the structure within a single day.
Project duration.
Requiring injection
Customer satisfaction
Geobear was appointed to stabilise a semi-detached residential property in Co. Wicklow that had developed significant subsidence affecting the junction between the main house and a single-storey rear extension.
Extensive cracking was visible both internally and externally. Internally, cracks had propagated through walls and ceilings, while differential movement had resulted in uneven floors and cracked ceramic floor tiles. Externally, substantial masonry cracking confirmed ongoing structural movement.
Site investigations identified that the property had been constructed on a raft foundation. The underlying cause of the movement was a failed drain located adjacent to the affected area. Water escaping from the damaged drain had saturated the surrounding ground, washing away and weakening the supporting fill beneath the raft foundation, leading to differential settlement.
Drain-related subsidence can rapidly undermine the support beneath shallow foundations. As the supporting material softens or is eroded, voids develop beneath the slab, allowing sections of the structure to settle independently.
In this case, the challenge was to restore support beneath the affected area without the significant disruption associated with traditional structural repairs.
The close proximity of the extension to the neighbouring boundary further complicated the use of conventional excavation-based solutions.
Traditional mass concrete underpinning was considered the principal alternative.
While underpinning would have stabilised the property, it would have required extensive excavation around the foundations, several weeks of construction activity, heavy plant, concrete deliveries and significant disruption to the homeowner.
A more extensive option of demolishing and rebuilding the rear extension was also considered but was rejected due to the cost, programme implications and unnecessary loss of the existing structure.
Following repair of the failed drainage system, Geobear stabilised the affected foundations using its engineered geopolymer injection solution.
A total of 15 injection points were installed around the affected walls. Through small drilled access holes, the expanding geopolymer resin was injected approximately 2 metres below foundation level, where it filled voids, strengthened the weakened ground and restored support beneath the raft foundation.
The lightweight material expanded in a controlled manner, improving the bearing capacity of the supporting soils while avoiding additional loading on the structure.
All works were completed using Geobear's self-contained mobile injection unit, eliminating the need for excavation, heavy construction equipment or removal of spoil from site.
Compared with traditional underpinning, the Geobear solution delivered significant programme and customer benefits:
By strengthening the weakened ground rather than replacing it through excavation, Geobear provided a fast, engineered solution that restored stability while allowing the homeowner to avoid the disruption, cost and programme associated with conventional underpinning.
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