Developer
Challenge
A new-build house had tilted on its raft foundation, leaving floors sloping at about 1 in 60 and walls cracked.
Solution
Geobear slab lifting solution designed to raise and re-level the raft in about seven shifts, avoiding mini-piling, jacking or demolition and rebuild.
Lift achieved
Raft foundation
Time on site
The property is a two-storey detached house built as part of a new housing development. Like the other homes on the estate, it was built of load-bearing masonry on a reinforced concrete raft foundation.
Following discovery of a slope in the floor, engineers inspected the house. The structural engineer found that the raft had rotated, with the house tilting down towards its front left corner by the bay window, and concluded that a substantial remedial solution would be needed to correct it.
The housebuilder approached Geobear in early 2025 to ask whether the building could be lifted using geopolymer injection rather than the conventional options. After further ground investigation and a full lifting target survey, Geobear’s re-levelling solution was accepted and delivered in March 2026.
The inspection recorded vertical cracking of 1–2 mm beneath the ground-floor bay window, stepped diagonal cracking under ground- and first-floor windows on the flank wall, a 10–15 mm gap at the movement joint between the house and a rear patio retaining wall, and visible misalignment between the house and its neighbour. Wardrobe doors in the front bedroom slid towards the front of the house under their own weight.
Spirit level checks indicated a floor slope of about 1 in 60 from back to front and from right to left. Applicable standards give an acceptable angular distortion limit of 1 in 400 for rafts on engineered fill, so the estimated tilt was far outside that limit.
The housebuilder’s record drawings showed the footprint straddling the edge of a former lagoon that had been infilled. The structural engineer suggested that poorly compacted fill in the lagoon could be the cause. A ground investigation in January 2026 drilled two windowless sampler boreholes to 8 m and found Made Ground to 5.70 m at the rear and 7.05 m at the front, over Clay, Siltstone and Mudstone.
The structural engineer identified two conventional ways of correcting the tilt: installing mini-piled foundations to stabilise the raft and re-levelling the house with hydraulic jacks, or demolishing the house and rebuilding it on piled foundations, which the engineer noted might prove more cost-effective.
Either option would have meant major works to a finished home. Mini-piling through up to 7m of made ground would need piling rigs, excavation around the raft and a jacking and transfer structure. Demolition and rebuild would mean losing the house altogether, with a new foundation design, construction programme and building control approvals before the home could be sold or reoccupied.
A Geobear slab lifting solution works through small holes drilled through the raft, lifting the existing foundation in place with no excavation and no change to the structure above.
Geobear designed a slab lifting solution using targeted geopolymer injection to lift the raft foundation of the house. The treatment was in two stages: a first injection below the raft to condition the made ground and give a firm base to lift against, followed by lifting injections immediately beneath the raft.
Before mobilisation, the housebuilder removed the staircase, kitchen units and floor coverings, disconnected services that could restrain the lift and commissioned a CCTV drainage survey. Geobear lifted the raft in controlled passes of about 10–15 mm, always starting from the lowest part of the house and bringing each set of points up to the level of the next before moving on. When a perimeter point was injected, the nearest internal point was injected too, so that the raft and walls rose together. The surveyor re-measured levels and reconfirmed targets after every pass, with real-time monitoring of the walls and raft throughout.
The works were undertaken within seven shifts in March 2026.
Verification
The property was lifted to the satisfaction of the client
Interruption
The Geobear solution kept the existing house and foundation in place and avoided piling, excavation, demolition and rebuild.
Key project outcomes
Geobear slab lifting solution designed to address an estimated 150 mm differential settlement of a 62 m² raft
Lift of >120mm achieved, monitored by an independent surveyor
Raft lifted in place through small drilled holes, with no piling, excavation or demolition
Undertaken in seven shifts and completed in March 2026
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