Underpinning is an effective foundation repair method that can strengthen and stabilize foundations with problems. Underpinning precision concrete construction is usually done to fix differential settlement. It occurs when the foundation sinks unevenly into the soil. The foundation is put under a great deal of pressure by differential settlement, which can cause structural damage. Underpinning the foundation raises this area again.
Why does differential settlement occur?
Different things can cause differential settlement, such as:
This soil is prone to swelling and shrinking as it dries. The soil beneath the home will move, causing differential settlement.
Erosion-prone Soil: soil that is prone to erosion will wash away, leaving voids beneath the foundation. You’ll get differential settlement if the foundation sinks in the voids.
Thirsty roots of trees – Roots that are looking for moisture can “drink”, or take, water from the soil. This leaves voids.
The soil must be compacted before any building can take place. This is important because if it’s not done right, then the structure could settle in the ground once built.
Downhill creep is the gradual movement of soil from the top to the bottom of a slope. It can lead to structural problems and differential settlement for the foundation.
Natural disasters: Earthquakes and floods can cause differential settlement.
Excavation near the foundation: If your neighbor digs a large hole right next to your house, this could cause the foundation to be unstable and result in differential settlement.
It is vital to have downspouts that divert rainwater away from your foundation. If you have foundation problems, it is important to ensure that your home has proper drainage.
What is the purpose of foundation underpinning?
We have just mentioned that differential settlement is the primary reason to underpin a foundation. But differential settlement is not the only cause for a foundation to need underpinning. You may also need to underpin a foundation if you plan to remodel your home or add an addition.
Installing piers to stabilize and lift a foundation will ensure that it is stable for years.
What is the process of underpinning?
Push piers or helical pilings are the two main methods of underpinning. The choice of underpinning method depends on a number factors including weight and condition. The weight of the structure is used to drive the push piers into the soil and install them on the load-bearing soil. Helical piers must be installed and monitored as they screw into the soil beneath the home. Once the brackets and helical pier have been installed, the brackets will be attached to the foundation. Then, the loads will be transported and if necessary, lifted to the installed pier system. Helical piers are also used for additions, new homes and porches. This is to ensure that the foundation will be poured on these helical pilings, not weak clay soil.
Push Piers are generally installed as follows.
The soil surrounding the foundation must be excavated to the level of the footing.
At intervals, heavy-duty brackets made of steel are placed on the foundation in the areas that will be underpinned. The brackets are used to support the piers.
Push piers can be driven in the ground by using hydraulic pressure. They are then pushed into the soil until they have reached the load bearing soil.
After the piers have been installed, the brackets and a hydraulic lift system are used to raise the building up to its maximum practicable level. The building will be raised to the maximum practical level without damaging it.
After the excavation, all that remains is to replace the soil.