Underpinning is the process of repairing or reinforcing existing foundations by adding additional foundational material. Underpinning is especially common on structures that have suffered from subsidence! Subsidence is the loss of earth or foundational material underneath a structure which has caused the building or part of it to begin to sink, which in turn causes cracks or warping to the property.
The subsidence may have been caused by a number of issues:
- Water flow washing away surrounding material or seismic activity shifting the earth beneath the foundations, which has caused piles to shift out of place.
- The original foundations being old and not up to modern day standards or them becoming damaged or eroded over time, which has in turn caused the piles to become uneven.
- The structure of the building changing can also cause subsidence. For example, if adding an extension on the side or an additional floor on your building, this will change the load placed on the foundations. The new, uneven load will cause your foundations to skew out of alignment.
- The structure or composition of the soil has changed, such as the soil drying out and contracting due to nearby vegetation or trees. The dry soil is then easier to wash away or to give way under the weight, leaving empty voids which can cause subsidence.
Subsidence can cause serious issues with any structure. Sloping floors, warped interior or exterior walls, and even cracks appearing in the brickwork, are all common signs of subsidence causing damage to your property. When it reaches its most extreme, subsidence can cause a building to split in half!
Underpinning requires the adding of piles or the lengthening of existing piles in order to increase their load bearing capacity. This can be done by excavating the area underneath piles to lengthen them or through using mini piles to reinforce the existing foundations. Addressing the root cause of subsidence quickly is vital to save a building from becoming unviable and, eventually, inhabitable and derelict. Only by underpinning to repair and reinforce the current foundations can you save the structure from this unfortunate fate!
