Posted on: 13 May 2020Share
Several factors can cause the foundation of a residential building to weaken over time. For instance, underlying soils or debris beneath the foundation can decompose or consolidate over time. In some regions, sinkholes might lead to settling of structures because soils move into the void. Moreover, soils beneath a foundation can weaken with time due to insufficient compression. All these factors can deteriorate a foundation, which might require you to stabilise soil to support the foundation in a process referred to as underpinning. Here are considerations for homeowners when performing foundation underpinning.
The role of a structural engineer is integral in the foundation underpinning process. Remember that during foundation underpinning, soils from the existing foundation must be removed by excavation. Such an undertaking can undermine the structural integrity of a building if not done properly. Therefore, a structural engineer should be consulted before you begin an underpinning project. An expert will assess a building to determine the depth of excavation based on the soil composition. Also, an engineer will determine the best method for underpinning the foundation.
Note that during underpinning, excavation is done in stages referred to as pins, whereby one pin has to be completed before moving to the next. In this regard, a structural engineer can guide the process of underpinning to ensure safety.
Mass Concrete Underpinning
In this technique, a segment of soil below a foundation is excavated in controlled stages. The excavation is done to a point where suitable soils are reached. Concrete is then filled in the excavated space and given time to cure. The new concrete forms a new foundation below the existing one, which ideally improves the stability of a building. After curing, a contractor moves to the next section until an entire foundation is reinforced. Mass concrete underpinning is popular because it does not require sophisticated equipment and is cheap to perform. Moreover, you can continue to use a building while the underpinning process is ongoing.
Underpinning With Piles
Piles refer to vertical structural elements that are driven in the ground near a foundation, using a hydraulic jack. If deep underpinning is required to stop the settlement of a building, then you need to use piles. Pile underpinning goes below the subsidence zone and is ideal if unfavourable soils are too deep for excavation by hand. Notably, various pile underpinning methods can be adopted. Besides, piles can extend below ground depending on the conditions of the soil. The process of driving piles is done until the bearing capacity of the structural elements is gained. Using piles to underpin a foundation eliminates vibrations and noise. However, care should be taken not to damage a building when jacking down the piles.