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The Importance of Underpinning in Foundation Repair

When it comes to foundation repair in residential homes, underpinning is just about an indispensable method in ensuring the structural elements of your home remain undamaged. For homeowners who are seeing cracks in their walls, floor or deciding to add a new storey — underpinning foundations is a must.

As a general rule of thumb, if you’re noticing cracks that are around a quarter of an inch in width, you’ll need to have your foundations underpinned. Whether you’re dealing with slab subsidence, wall cracks, sunken concrete or something else entirely, you’ll have to consider underpinning.

There are a few different ways homeowners can go about underpinning their foundations to prevent irreversible damage, and we’ve gone over a few of these below.

What is Underpinning

In short, underpinning is essentially the installation of new, more substantial footings or concrete bearers below the home with the aim of preventing any future movement.

When there are cracks creeping up walls, obvious tilts in walls or sunken floors in a home, it’s important to understand that this will generally be as a result of poor foundations. The movement, sinkage and compression of foundations, if left unchecked, will ultimately degrade a home’s structure and may eventually lead to it being demolished.

With the help of a structural engineer and a wall crack repair team, such as Buildfix, your home will generally be underpinned by either structural resin, wall ties, new footings or new screw piles and brackets.

When Does a Home Need to be Underpinned

As you may have guessed, underpinning becomes necessary when there is any significant movement being experienced in a house’s foundations.

If supporting walls or pillars are resting on a foundation that isn’t sturdy, this movement will transfer from the floor through the entire house, potentially warping it or in the worst cause, causing a collapse. 

However, not all movement requires underpinning. In soils such as clay, your home will routinely experience movement with season changes, and this issue cannot be easily rectified with underpinning.

When to Underpin

If footings have dropped
If slabs have become uneven
If shifting ground has majorly altered footings

When Not to Underpin

In reactive soils which can be combatted

Types of Underpinning Techniques

A variety of conventional underpinning techniques exist which can assist or hinder foundation repair depending on the problem at hand. From screw piles and brackets through to full-foundation piled rafts, there are a few options you may need to choose from.

Take a look below at the most common underpinning methods.

Screw Piles and Brackets

One of the more prevalent underpinning methods for homes in Australia with complex conditions is the screw piles and brackets method. This method typically relies on a bobcat or small piling rig, which will dig all-new foundations for which the screw piles and brackets can be installed.

In most cases, this method is quickly completed and can be undertaken by just a few crew members.

Pile and Beams

A second rather standard underpinning method relies on piles and beams to be installed alongside the foundations beneath structural walls. In this process, you’ll see your home’s wall foundations effectively ‘hugged’ by the new piles and beams that prevent movement and left or right tilts.

There are a few standout benefits to pile and beam underpinning, primarily the extremely high load capacity and the reduced surface disruption.

Piled Raft Underpinning

The underpinning option for the more severe foundational problems is the piled raft technique, which is utilised for entire-foundation underpinning. For homes with exceedingly deep foundations, and where all other underpinning methods become impractical, piled raft undermining is the remaining option.

The piled raft technique will require specific load-bearing locations in a home’s foundation to be located and the footings below these areas will then be strengthened with needle beams. These beams will then reinforce existing footings, support loads and prevent movement above.

Why Underpinning is Essential

In all, underpinning is key to preventing long-term and irreversible damage to your home’s structure.

If left unchecked, foundation movements and subsidence can cause walls to warp or crack and may even leave your home failing structural integrity testing, costing a fortune to repair if restoration is an option.