Underpinning is the process of strengthening the foundation of a building to give it more of the stability needed to support the entire structure. For instance, a foundation can be weakened by factors such as cracks or subsidence of the earth below it. Most importantly, underpinning is a restorative process that is mostly done in old buildings, which prevents settling, sinking and leaning. Before engaging in an underpinning project, homeowners must understand factors such as the causes of foundation problems, the structure of the foundation, and its support mechanisms. Here are some facts that homeowners should know about an underpinning project.
Weak Soils -- The soil beneath a foundation is integral in supporting the foundation of your home. A common factor that causes instability in foundations is unstable and weak soils. Excavations near your home might cause the soils to shift, leading to gradual weakening of your foundation. Further, subsidence, which is the movement and shrinking of the earth below the foundation, can also contribute to a weak foundation. For example, if you built your home on clay soil, you are likely to experience subsidence because the soil retains a lot of water and shrinks during dry seasons. The shrinking will cause the ground to become unstable, thereby causing cracks in the foundation, necessitating an underpinning job.
All Possible Causes -- Besides poor soils, structural weakening of the foundation can be caused by other factors such as earthquakes and tremors, plumbing leaks, material corrosion and temperature fluctuations. A thorough inspection is the only sure way of determining the exact cause of structural failure before you get started on an underpinning project. Knowing the cause of the problem can help put adequate measures to prevent a repeat of the issue shortly.
Mass Concrete Pour Method -- One of the most common approaches of underpinning a foundation is the mass pour method. Sections of the foundation are excavated to a certain depth, as specified by your structural engineer. After that, concrete is poured in these pits to repair the damaged infrastructure and maximize its stability. This method is acceptable for many homeowners because it is cheap and requires the use of simple hand and power tools.
Resin Injection and Polymer Grout -- In this approach, you do not need to excavate the foundation. All you need to do is drill a couple of holes in selected sections of the foundation for injecting the wet resin, which is absorbed by the soil. The resin will eventually dry, thereby completing the binding process with the ground, which reduces soil reaction. Alternatively, you can use a polymer grout for the resin. The polymer is often employed in sandy soils to bind molecules for added stability.