What is underpinning a house?
If your building or home foundation is failing, underpinning is the ideal way of reinforcing your existing structure. The process requires strengthening the property’s foundation and ensuring it rests on more supportive soil.
Types of Underpinning
There are three main methods used for underpinning processes, these include:
Concrete Slab
Concrete slab underpinning is a procedure that has been around for many years. Concrete underpinning is used to increase the size of foundations while also strengthening them. This process is expensive and messy.
Screw Pile
This underpinning method combines steel piers with concrete footings, to secure the building and ensure it is lifted back into its original position – closing all gaps and cracks. This process is also very expensive and requires major excavation.
Resin Injection
Resin injection is the newest but proven method of underpinning available. It is cost-effective, quick and clean.
It involves injecting an environmentally friendly liquid resin into the foundations through a small hole. The resin flows through the ground and expands into a solid gel. This places pressure and pushes on the ground and surrounding soil. As more resin is injected, it will lift the building above. However, this process is not suitable for all ground conditions and will require a professional consultation before you can go ahead with it.
To help you better understand the process of underpinning and when it is needed, our team of professionals at Resinject have outlined everything you need to know about the procedure. Read on to find out more about securing your building foundation with our underpinning services.
When is Underpinning Required?
Underpinning is required when you realise the original foundation of your home is not strong enough to support it.
Knowing when underpinning is required could save you from further issues down the line. For example, situations to look out for include:
- The soil which supports the foundation has changed (expanded, contracted, or been damaged due to plumbing left unrepaired)
- The properties of the soil were not fully understood at the original design of the foundation – so the foundation is not ideal for the specific conditions
- A new construction nearby has resulted in excavation of the soil that supports the existing foundations
- A natural disaster has occurred – such as an earthquake, flood or drought – which has caused the structure to move or become unstable
Do I Need Underpinning?
Now that we’ve covered the topic of what is underpinning, we can move on to understanding how you know when you need it. There are some clear signs to look out for.
While subsidence in most properties is common, actively occurring subsidence is what you need to be careful of. This includes:
Cracks in Floors & Walls
Most cracks in your property’s floors and walls are due to everyday wear and tear. This is nothing to be concerned about as they’re primarily superficial and minor.
However, more significant cracks are where the problem starts, as they often represent major underlying issues with the property, including uneven weight distribution from weak foundations.
Cracks that may mean you require underpinning can occur in the plaster, wall, floor tiles, brickwork, render, or concrete slabs. Ensure you’re tracking these cracks and noticing whether they get bigger, wider, or longer. If so, you will need to hire a team of professionals to perform an underpinning procedure.
Floor is not Level
While not as obvious to spot as cracks, identifying uneven floors is a significant sign that your house requires underpinning. When you feel that your floor is leaning to one side, you will most likely have foundation issues that need addressing.
In some serious cases, you could even stand on one side of the house and see the unevenness in the floor. This can also cause other issues, such as misaligned doors. Hence, while you might be able to tell when your floors are uneven, you will still require help from a professional to understand how significant the damage truly is.
Alignment Issues
Are your doors and windows not in alignment? This is a major sign that you’re having foundation problems.
When you see gaps appearing and getting wider around your doors and windows, then you require underpinning. This includes when doors and windows are hard to close or reopen, and you’re unable to lock them properly. In more severe cases, the misalignment may even be visible – meaning the door or window will begin to pull away from the surrounding walls.
Don’t let this evolve into a major issue. Get the assistance you need right away, before the foundation of your home begins to crumble.
Property Foundations & Footings
To fully understand what underpinning is, it’s important to understand what makes up the workings of a property. Hence, by using the term “foundation”, we commonly refer to both the footing and flooring system and how they come together to make the workings of a property.
In terms of flooring, there are two common systems used:
Slabs on the Ground
You may have heard of several types of slab-on-ground foundations. For instance, you can get a raft slab, waffle pod slab, slab with dropped edge beams, and even a reinforced slab on fill. These are standard foundation systems that have been tried and tested for many years in Australia.
Suspended Floors
Suspended floors are common foundations framed with stumps or piers and supported by bearers and joints. Talk to an expert to determine whether suspended floors are the appropriate system for your foundation.
Alternatively, there are also multiple footing systems that can make up your foundation. In residential construction, these include:
Continuous Footings
This includes a concrete strip or slab used to aid with evenly distributed loads.
Pad Footings
This footing is a square or round concrete pad used for supporting a concentrated load and used in combination with stumps.
Stumps
Stumps are designed in hollow steel or timber poles to support the foundational structure of your property.
Piles & Piers
Piles and piers are just like stumps; however, they are driven into the ground and commonly used when additional support is needed.
While it is important to understand the various foundation systems, the process of underpinning occurs most on slab-on-ground type foundations, especially when they begin to fail and need quick fixing.
Why Might Building Foundations Fail?
There are many reasons why building foundations fail. While many of these cases occur within an ageing building, there are a variety of reasons why foundations may end up needing underpinning as a solution:
Site Erosion
Erosion is a major problem, as it can wear away the soil fitted around the property foundations. This can become so bad that the foundations become structurally compromised. Erosion can form for numerous reasons, including a burst water pipe, uncontrolled water flow, insufficient drainage, and more.
Reactive Soils
Many foundation issues are caused by problems relating to the movement of reactive soils.
This can involve shrinkage, which can lead to settlement or expansion, and further causes heaving. When the environment is persistently dry, the soil will gradually lose moisture and start to shrink. Alternatively, the soil will begin to expand when moisture levels are heightened (perhaps through wet weather).
Shrinkage and expansion can both compromise the foundation of your property – often resulting in cracks and causing major issues further down the track.
Inadequately Compacted Fill
When a site has been subjected to fill, there may be times when the material used has not been sufficiently compacted, and therefore, cannot support the weight of the property. Hence, foundational problems usually arise from the poorly compacted fill.
Slope Failure
Slope failure is another type of foundation failure, related to the movement of the soil and how much the soil has slid downhill over time.
There are two types of failure to account for – slow failure known as “creep” and sudden failure known as “landslide”.
When a property or slope is failing due to creep, underpinning can usually be utilised to rectify the issue. However, this is dependent on the site and requires professional evaluation.
Surrounding Environment & Trees
Trees can be a significant factor in foundation failure.
This is because plants remove moisture from the soil in a process called transpiration. If your property contains plenty of large trees, the amount of moisture they draw from the soil can accelerate soil shrinkage.
Additionally, when trees are situated too close to properties, the soil can shrink enough to compromise its foundation.
Foundation Design
While this is not a very common issue, the design of the original foundation may be lacking – and so causing the foundation to weaken over time.
For instance, the soil properties may not have been adequately understood at the time of build, meaning the conditions are not appropriate for the property. If this is the case, you must seek assistance from professionals right away.
Underpinning Cost
Understanding how much you should be paying for underpinning services can be confusing, especially when you’re not getting clear information from contractors or structural engineers.
Underpinning costs rely on four key factors:
- What type of foundation is it?
- What has caused the foundational failure?
- How bad is the problem, and how much damage has it already caused?
- How easy is it to access the foundations?
At Resinject, we aim to keep our prices low while providing clients with high-quality underpinning services. If you’re struggling with the structural integrity of your home, the team at Resinject will guarantee results by securing your foundations without breaking your budget.
Is Underpinning a Permanent Fix?
While this is a difficult question to answer, underpinning will definitely help to secure the overall structure of your property.
Ultimately, a permanent fix will depend on a range of factors – such as the type of soil your property is sitting on and the type of underpinning service you choose to utilise.
However, it is essential to note that not all underpinning is appropriate for all foundation problems. Therefore, property experts, such as the team at Resinject, will conduct a property check-up before providing a permanent fix.
Alternatively, if underpinning is not the right solution for your property, we will recommend an alternate course of action.
When Should I Get Help?
While none of these factors guarantees the need for underpinning, it’s best to know for sure. You don’t want to wait around until the damage becomes severe – and even more expensive to fix. After taking a look for yourself and assessing noticeable damages around your property, the best thing you can do is seek professional advice.
Resinject offers a free structural assessment where we evaluate your property for foundation failure and provide you with the appropriate steps to make the right changes. This is the ideal first step in your journey to fixing your home or property.
Do you need an expert assessment? If you’re unsure whether your property requires underpinning, book a free assessment from our team at Resinject. Alternatively, if you’re looking for more information, contact us today.
