allenCO Construction

South Australia’s Premier Underpinning Experts in Adelaide

Structural Restoration & Foundation Repair Services

Underpinning in Adelaide – What is it?

Underpinning is the process of supporting or strengthening the foundation of an existing house, building, or similar structure so the structural damage of the home or property is repaired, and further damage and unsightly signs of a poor foundation are avoided.

It is required when the original foundation is no longer strong enough to support the building, and is usually the result of a change to the soil structure, whether due to the type of soil or an external influence on the soil.

Underpinning is accomplished by reinforcing the existing foundation. We do this by extending the foundation so that the load is distributed over a greater surface area to support the existing foundation.

When is underpinning needed?

For most homeowners, underpinning is required when the original foundation is no longer strong enough to support the house. This is usually the result of the soil supporting the foundation changes in some way or the properties of the soil were not adequately understood during the original design of the foundation.

There are quite a few factors, particularly during larger renovations or additions that lead to the need for underpinning. These are:

  • Poor construction of connecting extensions
    Where the original home connects with an extension, there can be differential settlement of the soil (soil settles at different rates between the original structure and the new extension), insufficient foundation support, and inadequate structural connections. These issues can lead to instability, cracks, and a lack of load transfer between the structures.
  • Soil erosion, typically from poor water drainage or damaged pipes
    When pipes are damaged or leaking, water can seep into the surrounding soil, causing soil erosion and weakening the foundation’s support. This erosion can create voids or empty spaces beneath the foundation, leading to settlement and potential structural damage.
  • Poorly compacted fill
    When fill material such as soil or gravel is not properly compacted during construction, it can settle and shift over time. This settlement can lead to an uneven or unstable foundation resulting in cracks, sinking, or structural damage.
  • The way the structure is used has changed
    When the purpose or occupancy of a building changes, such as converting a residential building into a commercial space or adding additional floors, the load on the foundation can exceed its original design capacity. This change in usage can result in excessive stress and strain on the foundation, leading to settlement, cracks, or structural instability.
  • New construction nearby
    If soil near the home is excavated (like for the installation of a swimming pool or the knock-down rebuild of a home next door), it can cause ground movement and soil disturbance. This soil removable or disturbance causing ground movement can lead to settlement or shifting of the soil beneath the existing structure, potentially compromising its foundation.
  • Increased loading causes existing footings to be inadequate
    When additional weight is added to a building, such as through the installation of heavy equipment, construction of additional floors, or adding a large rooftop solar system, it can exceed the original design capacity of the foundation. This increased loading can lead to settlement, cracks, or instability in the structure leading to foundation damage.
  • Leaking plumbing not allowing the soil moisture content to reach equilibrium
    When plumbing leaks occur, water can continuously infiltrate the soil surrounding the foundation, leading to uneven moisture distribution. This imbalance in soil moisture can result in differential swelling or shrinkage, causing the foundation to experience uneven settlement or movement.

What are the signs to look out for?

There are a few issues to look out for to know if underpinning may be required. These include:

    • Cracked walls
    • Uneven floors
    • Doors that no longer align to their frames
    • Windows that are hard to open
    • Persistently damp ground
    • Dry, cracked soil
    • Sagging or sloping floors or ceilings

How much does underpinning in Adelaide cost?

There are many factors considered to figure out the cost of underpinning your home or business. These include the scale of the work involved, the number of underpins required, obtaining an engineering report, the type of machinery required to complete the project, and the type of soil on your property.

Most domestic foundation repairs range in cost from $5,000 to $40,000 based on the variations mentioned, with each underpin costing roughly $2,500 to $5,000.

Large-scale more serious underpinning repairs and commercial underpinning repairs can cost up to around $80,000 or more, determined by the various factors mentioned.

What is the difference between concrete underpinning and resin underpinning?

Typically, there have been two main underpinning techniques used in Adelaide. These are:

      • concrete slab underpinning
      • screw pile underpinning, also known as pier underpinning or piering.

As our technologies and construction methods develop we find new ways of doing things. As a result, there is a new method in the market offering underpinning solutions called grout, or resin injection, though it is not actually underpinning.

Resin Injection

Resin injection involves injecting grout or resin into the ground to fill up voids under the foundation slab and expands, compressing the ground. Visually, the foundation can be seen to lift and repairs are considered to be a success. Whilst this method looks impressive and is a cleaner and cheaper alternative to the traditional concrete pier method, it has been shown that the resin is not penetrating into stable ground. Because this process is limited to the depth it can achieve which is approximately 1.5 metres, it is vulnerable and susceptible to movement and not considered a permanent solution.

Concrete Pier Underpinning

Traditionally, concrete underpinning was used to increase the size of foundations, and in the process, strengthen them.

Pier underpinning is combining steel peers with concrete footings to secure the building and lift it to its original position. Closing up gaps and cracks with concrete pier underpinning is considered a long-term solution, one that will not be affected by further changes in the ground surrounding the house or building.

What is allenCO construction’s preferred underpinning and foundation repair method?

There are a few different methods for underpinning, we use reinforced 4-metre concrete piers. We do this by excavating the original footings and pouring concrete underneath, before reinforcing it with steel to give additional strength and stability.

Once the concrete has cured (this typically takes around five days depending on damage and weather conditions) and if the foundation is considered structurally suitable, we are capable of lifting your foundation back to as close as possible to its original position by placing heavy-duty jacks on the reinforced concrete and the whole structure is jacked up, closing up cracks and voids.

What happens next?

When the cracks have been successfully closed, either heavy-duty props are positioned to stop the building from sagging again, or the jacks are left in place and more concrete and steel reinforcement are used to make the repairs permanent and strong. The job is finished once we are convinced the foundation is as strong as it can be.

Because the piers are extended to stable ground at four metres they are unlikely to be affected by further soil movement and is a permanent solution. And at allenCO construction, we guarantee our work will last.

The allenCO construction underpinning Adelaide team is considered to be one of the last old-school underpinners in Adelaide and South Australia. Using methods that are tried and true and competitively priced we can guarantee our work, ensuring your home, investment, or business is safe, will stand the test of time, and retains and grows in value for years to come.

Experts at underpinning Adelaide

If you think your home, investment, or business requires underpinning and foundation repairs, fill in the contact form below, or call our expert team to arrange a consultation – 0429 999 478

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