Underpinning

Traditional underpinning methods are fast becoming a last resort for property owners. The use of resin injection is a far superior method, which does not require excavation, as well as taking a fraction of the time of traditional methods. There is also no need for homeowners to leave the property whilst work is carried out.

What is traditional underpinning?

Underpinning is a method of ground strengthening which involves the excavation and expansion of the foundations which support the load. Underpinning work is a major task which requires the use of heavy machinery and excavation. Customers should carefully consider their ground strengthening requirements before underpinning work is agreed.

Underpinning may need to be carried out due to the following issues:

• Inadequate planning which fails to correctly identify the soil
• characteristics during the design
• A change in the soil conditions under the foundation
• The original foundation is no longer adequate
• Repair work/excavation in a nearby area has endangered the current foundations
• Additional floors are being constructed underground

Types of Underpinning

Mass Concrete Underpinning – The process of replacing the soil under foundations followed by concrete pouring. Typically used at shallow depths, box-shaped parts replace the soil in a pre-determined sequence.

Pilled Underpinning – A method of underpinning typically used at more substantial depths. During the underpinning process, steel cased piles that can be filled with concrete are installed. The piled foundations can be divided into three categories depending on the installation method, these are; driven piles, drilled piles and jacked piles.

Jet Grounding – A high velocity jet of cement grout is used in the creation of geometry of grouted soil. Jet grouting is typically used to create columns of grouted soil underneath an existing foundation. This method is effective across a variety of soil types. Jet grouting is also an effective method of underpinning as there is no need for load transfer structures. However, because jet grouting requires drilling and the use high-pressure, it is not always suitable for very sensitive foundations due to the soil disturbance caused.

Resin Injection Solutions – A much faster and efficient method of underpinning used for soil stabilisation and the re-levelling of floors. Injections o resin materials made up of multi-component, expanding materials replace the need for heavily pressurised, hydraulic systems. By providing a much less disruptive and safer alternative to other methods of underpinning, resin injection shortens the completion time of work to a matter of days, without the need for any excavation.