If foundations are faulty and in need of repair, or need deepening, the method of underpinning is used. It is generally used when there are plans to add additional levels to an existing structure or when the foundation has been damaged in any way.
One major sign that a building needs underpinning is when cracks become visible in the façade. If the cracks are wider then ¼ inch, there are signs of faulty foundations and if the cracks are diagonal then the building definitely needs underpinning. Foundation failures could also be considered as heaved foundations, cracked or buckled walls and concrete floors.
The mass pour method is the most commonly used method of underpinning. The process requires excavating sections in sequence to a pre-established depth below the footing. Concrete is then placed on each pit. The sequence is repeated until the entire affected area has been underpinned. There are other methods and techniques to underpinning which are:
Underpinning with Screw Piles and Brackets
This method is used in certain instances when traditional underpinning is not possible. Some buildings might require excavation up to great depths, or maybe it is unfeasible to use a piling rig. Screw piles and brackets require only a two-man crew who can install them by hand, using small equipment.
Screw piles are able to withstand vertical and lateral wind forces, vibration and shear forces and have the capacity to work in tension and compression. They are ideal when used with underpinning support brackets as the structure can then be lifted back into a level position and the weight of the transferred to the pier and bracket system.
Pile and Beam Method
Another great way of alleviating footing is to use a pile and beams method. This system requires that a mini pile is installed on either side of the affected wall before brickwork is removed from below the wall and reinforced concrete needle beam is used to connect the piles and support the wall.
For underpinning and piling in Manchester, contact Rhino Piling today.
