What Does Foundation Underpinning Involve?

Foundation underpinning in Melbourne, also known as basement underpinning, is a construction method used to repair or strengthen a weakened or settled foundation.

Although underpinning is typically used as a foundation repair technique, it’s also recommended by landscaping professionals to prolong the life of a home.

If you’re a homeowner planning to invest in underpinning for your home, then you should learn the basics of underpinning since it’s quite expensive.

underpinning the basement of a house


The Basics of Basement Underpinning

One of the most popular underpinning technique uses piers and concrete. This technique is commonly referred to as a traditional underpinning method.

It’s a modification of an early underpinning technique that used concrete alone without piers. In this method, concrete makes the basement more durable whereas the piers work by increasing the load-bearing ability of the basement.

The process of underpinning is necessary for several reasons such as:

  • The basement is clearly showing major signs of damage such as extensive cracking, sinking, and moisture seepage.
  • The basement is allowing heat to escape from the home despite doing several repairs and adding insulation.
  • The basement requires strengthening to support the weight of additional floors to an existing building.
  • Construction of a large building nearby has led to soil compaction beneath the basement, thereby making the house unstable.


The Process of Basement Underpinning

Basement underpinning involves the following process:

Step 1: Creating Temporary Support

First, a temporary structure is built before starting the underpinning process. The support structure is built to make sure that the structure won’t collapse during the underpinning process. Besides, it offers a base for moving heavy materials such as piers.


Step 2: Excavation

Next, excavation is done to remove soil around and beneath the basement. Excavation allows for enough room to access the area beneath the basement, thereby creating space for installing piers for more stabilization.

Before excavation, you need to have a plan that outlines the spots and angles where the piers will be installed. Unnecessary excavation may weaken the structure further and prolong the project.

Square or round holes are drilled depending on the piers’ shape and the excavation tools being used. Typically, the holes shouldn’t be less than 24 inches away from each other.

Excavation tools used include soil loaders and backhoes to scoop out and pile the excavated soil. Using shovels is also an option, but they tend to make the process tiring and slow.


Step 3: Installing Piers

Upon creating enough space for underpinning, piers are introduced to offer extra support to the basement. The piers used are available in two types including:

  1. Helical piers- They’re installed by screwing them on a frame. They’re challenging to alter after installation since the secured framework can’t be undone.
  2. Resistance piers- They’re installed with advanced machinery that drives them into the soil. No brackets or screws are required to secure them in place. They’re ideal for use in bigger homes.


Step 4: Adding Concrete

Some builders prefer pouring concrete on the pier framework to enhance its durability while others pack garden soil. However, concrete offers more strength.

Basically, the outer edging of each pier is secured on the basement perimeter by pouring a sufficient amount of concrete. Once the concrete settles and hardens, the temporary structure for supporting the basement is removed.

Generally, concrete is poured using traditional methods such as the use of shovels, concrete rakes, and trowels. The outer edging of the poured concrete is smoothened with a handy concrete cutter.


Read: The Process of Foundation Underpinning Explained