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24 June 2019
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FOUNDATIONAL CONCERNS

Robbie Blanchfield explores the benefits of resin injection in buildings. 

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04 February 2019 | Robbie Blanchfield 


Early indicators that a building has foundation problems because of subsidence include cracks in walls, jammed or misaligned doors and windows, and sloping or sinking floors. Subsidence can happen for many reasons such as neighbouring construction or soil that is too wet or too dry.


There are two key methods to deal with subsidence: concrete underpinning and resin injection. Concrete underpinning has been used for over 100 years and has been the go-to solution for strengthening foundations affected by soil subsidence.


Resin injection is a modern alternative that has been used for about 20 years, particularly in Australia, the US and Asia. 


What is resin made of?

The resin is a proprietary geopolymer formula that has been developed over 20 years. The environmentally inert, closed-cell material has low global warming potential that complies with EU standards.


How is it applied?

The resin mix is delivered into the ground through small-bore injection tubes around a building or structure. A chemical reaction and consequent expansion occurs as the components mix together when entering the ground. 


The reaction and expansion strengthens the ground and the structure or building is returned to level in a controlled manner. The resin forms a strong, long-lasting and stable material. Constant monitoring by a laser levelling system is required to assess how much resin is needed and when the building is level again.


How quickly is it applied?

Resin injection is more efficient than traditional concrete underpinning. Depending on the size of the task, most house relevelling and slab-lifting takes less than a day and, once work is completed, concrete slabs and driveways can often be driven on within hours. 


Longevity

The lifespan of resin can differ depending on the formulation and the manufacturer’s warranty but ours is 20 years.

Other factors can affect the longevity of remediation works. Paying attention to surface drainage, the maintenance of water services and the removal of tree roots will also improve longevity. 


Examples of resin in use

Resin injection as a subsidence remedy has a range of benefits that can be seen immediately after its application. The process is fast and non-invasive, eliminating any need to vacate the premises. 


For example, when an 800 square-metre manufacturing facility in Merseyside began to subside, causing the floor of the facility to dip by as much as 280mm, it created a hazard that needed urgent repair. This level of subsidence would have required an enormous amount of invasive work if concrete underpinning had been used.


The project was on a tight schedule that required the work to be carried out around staff, fixtures and machinery while allowing business as usual. By applying resin through targeted injection points and using laser levels to monitor the progress, the work was completed within two weeks.


Resin injection is also used on homes. A house in Devon on unsuitable foundations had shifted 40mm, causing a wall to separate from the foundation, leaving a large crack. The process was used to lift the home’s foundations by 43mm and the house itself by 20mm, returning it to its original level and reconnecting it to its foundations. The work took only three days to complete, without disrupting other nearby renovation work. 


Resin injection is a sustainable and responsible solution that focuses on preservation rather than replacement and it doesn’t affect groundwater, soil quality, or local wildlife – making the process environmentally neutral.  


Robbie Blanchfield is commercial manager at Mainmark