Side extension underpinning
Most side extension buildings are built next to the neighbour wall. There are few ways to build the trench next to the existing foundation or to underpin. Underpinning is an extra support of the existing foundation
Usually the decision is done based on the Structural engineer and the Party Wall agreement requirements of your neighbour.
Mass Concrete Pour
This method involves digging holes underneath the existing foundation in sequence and filling them with concrete, often with reinforcements. Depending on the specifics of the project, this work can be done by hand without the need for heavy excavation equipment.
The Beam Method
The beam method is a take on the mass concrete pour method. Holes are dug at strategic points under the wall and filled with concrete. A load-bearing beam is then placed on them to spread the weight of the wall above.
The piling method is more suitable for situations where deep foundations are required, often more than 5 metres. This system requires specialist equipment and expertise and is often the most expensive option.
The cost of the underpinning of the side extension will depend on few factors as width and depth of the foundation, party wall agreement, type of the underpinning and building control if may require additional works.