The term underpinning refers to a few methods of bracing up a home's foundation and the surrounding ground. This is typically done if there is damage to the foundation, if it will be bearing more weight (such as when another story is to be constructed) or if a property is prone to sinkholes and other ground stresses.
There are a few different methods of underpinning your home's foundation and each has its own pros and cons. Consider a few important factors about those methods so you can choose the right one if your home needs to be underpinned.
Mass Pour Method
This is the most common method of underpinning. With the mass pour method of underpinning, sections are excavated below the footings of the foundation and concrete is poured into the pits. It then sets and the foundation is strengthened.
The mass pour method is very easy and affordable. While it's best left to a professional contractor, a homeowner with some understanding of pouring concrete can handle this job on their own. However, it typically cannot be used if the job requires a very deep excavation as this itself can weaken the foundation.
Screw Piles and Brackets
This method is commonly used where the mass pour method is not feasible. It is also relatively simple, with two persons able to complete the job with a mini excavator and a few other specialty tools. The screws are placed into the foundation and set with brackets so that large cracks and other damage will not allow the foundation to crumble completely.
This method also offers the advantage of minimal vibration needed for installation. Vibrations can cause even more damage to foundations, especially if they already have large cracks and fissures. The screw pile method protects the foundation as it's being applied, making it a good option for many buildings.
Piled Raft Method
This method of underpinning is often used when an entire structure needs underpinning. Piles are placed at various locations around the foundation and then pockets are formed by breaking the foundation itself. Reinforced needle beams are then inserted into those pockets, to bear the weight of the foundation. A ring beam is added to connect all the needle beams and concrete is then poured over the entire underpinning structure to close it up.
A contractor like Harman Contracting Pty Ltd can advise you on the best type of underpinning method for your home or other structure, but note these differences in methods so you understand which one might be the best choice for you.
