Stabilising the foundations and slab in a detached house
Each year Geobear remediates hundreds of residential properties that have suffered from structural movement caused by subsidence.
The teams work in all corners of the UK dealing with subsidence issues that have occurred for many reasons such as shrinkable clay soils or drainage problems.
At a detached house in Nottinghamshire, the owners who had recently purchased the property were alarmed to find cracks in the walls behind plaster and evidence of a sinking concrete slab.
Following a Geobear site assessment, it was established that a broken drain had caused wastewater to seep into the soils beneath the property. Water affects the integrity of granular soils, meaning it can wash away and loosen. The impact of this effect is subsidence, which is the structural movement of a property caused by a change in the geology of the ground beneath.
The customer in this instance had a number of options. They could repair the drains and leave the property as it was, patching up cracks and hoping no further movement would occur. Alternatively, they could look to underpin the property.
Underpinning is the process of preventing the structural movement of a building by adding further concrete beneath existing foundations. This process requires the excavation of soil beneath the existing foundation and replacing it with concrete. Underpinning is a labour-intensive activity, depending on the extent of a problem can take many weeks or months to complete.
In this case, the customer decided to choose a Geobear geopolymer injection solution.
The process of geopolymer injection is a direct alternative to underpinning. The result of the process is exactly the same, in that it prevents any structural movement. However, due to the nature of the process, which features the introduction of expanding geopolymer material beneath the existing foundation, a building can also be lifted slightly which can cause cracks to close.
At this property, the leaking drains had caused the structural movement to the left and rear of the property causing cracks to appear. Additionally, within the footings, the concrete slab had also sunk. This required Geoebar to design a treatment plan that would improve the existing soils beneath the foundations and slab to prevent further movement.
The Geobear regional manager that visited the property designed a treatment plan based on the evidence from the site. This plan was then assessed and approved by the Geobear engineering team and signed off by a chartered engineer.
Geobear’s solution usually takes one day to deliver. In this case, the technical team arrived on-site at 08:00 and were finished before 17:00. The team followed the specified treatment plan and injected the expansive geopolymer material at incremental locations beneath the foundations.
The customer received a certificate of structural adequacy and insurance backed guarantee following the works.