Underpinning versus resin injection: choosing the right underpinning solution for foundation issues
With unique climates and landscapes, homes in Australia and New Zealand face diverse ground conditions that can cause subsidence, affect building foundations and result in structural issues.
While most issues are due to unstable ground, extreme weather conditions including drought and floods can be common contributors to subsidence. Other factors such as leaking pipes or inferior concrete foundations can also be a cause.
The first tell-tale signs of subsidence often appear in the home as cracks in walls, sinking or sloping floors, or doors and windows that won't close. While minor cracks are not usually cause for concern, large cracks and misaligning doors and windows can be signs of something more serious and should not be ignored. Cracks which are wider than 5mm or big enough for you to insert your little finger in them, or zig-zag/stepped cracks in brickwork which usually follow the mortar lines, are big indicators of possible structural problems.
While the anticipated cost to rectify foundation damage may seem prohibitive, the rectification costs do increase over time as the situation gets worse and not addressing the issue can significantly devalue the property. There are several solutions to consider, including traditional methods like concrete underpinning and the more cost effective, non-invasive resin injection solution, to help resolve structural problems.
Concrete underpinning: an expensive, labour intensive process
Historically, concrete underpinning has been the go-to solution for strengthening foundations affected by soil subsidence. This tried and tested method has been used for more than 100 years, however, it is a costly and time intensive process that can take weeks to complete. It's also inconvenient for homeowners who are generally required to vacate their home while the work is being completed.
Depending on the extent of the issue, homeowners may also need to consult with external engineers and gain appropriate council permits before commencing the underpinning work which can add weeks to the project. Once work begins, cement trucks and other heavy vehicles will need to transport concrete, tools and machinery onto the site, adding further disruption and chaos. Homeowners may also find that existing plants and landscaping are damaged around the home's perimeter.
The underpinning process:
Excavation: heavy machinery is required to dig large holes under the home, with extensive digging to depths often up to 3 metres.
Soil removal: large quantities of dirt and rock are loaded onto dump trucks and transported away from the site.
Pouring concrete: filling the holes or "piers" with concrete can be complex and logistically challenging depending on the site (a typical suburban home may require as many as 24 concrete pours to fill the piers), and concrete mixers will need access to the site.
Curing time: concrete can take several days to set, depending on circumstances including the weather, adding more days to the project timeframe.
Resin injection: a faster, smarter, less-invasive solution
If concrete underpinning sounds logistically and economically unfeasible, there is good news for homeowners concerned about the structural integrity of their home. Modern resin injection solutions can be used to successfully remediate homes affected by subsidence in significantly less time than it takes for traditional concrete underpinning.
Mainmark's proprietary Teretek® engineered resin injection solution is a proven, cost-effective and quick alternative to more invasive methods. Using a process similar to keyhole surgery, the work can often be completed in one day. It is widely used to strengthen foundations, re-level buildings and remediate issues for residential, commercial, industrial, mining and infrastructure projects.
The resin injection process includes:
Initial site inspection: The Mainmark expert arrives on site for an initial consultation to carefully assess the property, identify the optimum resin injection points and provide a quote.
The Mainmark 'rig': On the day, Mainmark technicians arrive on site, typically in a single truck or 'rig' which contains all the equipment required to complete the project. There is no need for messy excavators or concrete trucks on site and the team work quickly and discreetly.
Resin injection: Once the home's services have been located and resin injection points have been determined, Teretek is applied through tiny holes, typically 6mm to 16mm in diameter. The resin expands in the ground within minutes, instantly placing pressure on the ground and compressing the surrounding soil. The home is constantly monitored using laser levels. Once the resin is in the ground, it remains inert and does not break down. The process is clean and quiet, has minimal impact on homeowners or neighbours, and leaves gardens and landscaping undisturbed.
Resin injection strengthens and improves the ground beneath a structure. By using Mainmark's Teretek resin injection solution homeowners will experience immediate results:
Windows and doors will work properly again
Gaps between skirting boards and sunken floors will realign
The key thing to remember is that only underpinning experts are qualified to treat structural issues. Always choose a professional that is willing to work with you to ensure the fix does not cause more extensive damage than the original problem.
By James O'Grady
James O'Grady is the Sales and Business Development Manager at Mainmark. He is a civil engineer with 25 years' experience in structural engineering, construction materials and ground treatment.