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New Zealand
Overview
The Modern Alternative To Underpinning
Traditional underpinning involves digging deep holes next to the footings of your home. This method disturbs your gardens and pavements, often taking weeks to complete.
Underpinning involves mass concrete pouring to widen a foundation, or installing piles to transfer loads to deeper soils.
Your house might be built on soft or expansive soils. In this situation, if only part of the footing is underpinned, differential movement can occur between the underpinned areas and the rest of the house. This can result in new damage to the parts of the structure not underpinned.
The Non-Invasive Solution
Mainmark provides an alternative to traditional underpinning. Our non-invasive, engineered solutions can bring your house back to level. Ground improvement enables the foundations to carry greater loads. It also reduces how much settlement or movement happens across your house from season to season. Our Teretek or Permeation Grouting technologies can be used for ground improvement in suitable soils.
If your house has experienced sinking, our re-levelling solutions can improve the ground beneath your house. We can also carry out ground improvement to mitigate further damage. Mainmark use the Teretek and JOG technologies, which are versatile and suitable for re-levelling both simple and complex structures.
Teretek uses a method of injecting polyurethane resin beneath your house. As the resin expands, it gently lifts the structure. This is also a non-invasive and cost-effective solution.
JOG is a multi-point injection system which uses cementitious grout to re-level your entire house all at once.
How we get your home back to level
Benefits
Mainmark’s Level Correction Methods
Fast
Our technologies have fast curing times and treated areas can be used immediately or without the delays compared to traditional repair methods.
Environmentally Inert
Our technologies use an inert material that is non-toxic and does not leach into the environment or affect the treated area.
Non-Invasive
Our solutions are of surgical nature compared to traditional methods.
Cost-Effective
Compared to traditional methods, our solutions are more cost-effective.
Get a quote
Arrange a site assessment in 3 simple steps:
Step 1
Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.
Step 2
Our friendly customer service team will be in touch to schedule a site assessment that suits you.
Step 3
One of the Mainmark experts will visit your home or property, assess the damage, and ascertain the likely cause. They will establish the approach needed, creating a plan specific to the needs of your building and provide you with a detailed quote.
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Underpinning Frequently Asked Questions
What is underpinning?
Underpinning a house foundation is the process of strengthening an existing foundation, usually when it has become unstable or is no longer capable of supporting the structure. This process is typically performed when there are signs of foundation settlement or shifting, such as cracks in the walls, uneven or sinking floors, or doors and windows that no longer close properly. Mainmark provides underpinning in Auckland, Wellington, Christchurch and across New Zealand.
What is chemical underpinning?
Chemical underpinning, also referred to as resin injection, is an innovative non-invasive solution used to provide ground improvement and enhance the load-bearing capacity of a structure’s foundation.
This method is particularly useful in situations where the foundation soil has insufficient strength or when the soil’s characteristics have changed over time, reducing its ability to support a structure.
What is the underpinning procedure?
The underpinning procedure involves a series of steps designed to strengthen or stabilise the foundation of an existing building. The exact procedure can vary depending on the method of underpinning chosen (e.g., mass concrete, mini piles, etc.) and the specific needs of the building.
When does a house need underpinning?
Underpinning is a method used to strengthen the foundation of a building, often when it has been compromised due to soil movement, settling, or other structural issues. Identifying the need for underpinning early can prevent further damage and more expensive repairs. Here are the key signs that may indicate the need for underpinning:
1. Visible Cracks in Walls or Foundation
Large or Growing Cracks: If you notice large cracks, especially those wider than 1/8 inch, that continue to grow over time, this could indicate a shifting or settling foundation. Cracks may appear in walls, ceilings, floors, or the foundation itself.
Diagonal Cracks: Cracks that appear at an angle, especially near doors, windows, or corners, may be a sign of foundation movement, requiring underpinning to stabilise the foundation.
Step Cracks: Cracks that follow the mortar lines in brick or masonry walls can signal a shifting foundation, often seen in older buildings.
Sagging or Sloping Floors: If you notice that floors are uneven, sagging, or slope in certain areas, it could indicate that the foundation is settling unevenly, which may require underpinning to correct.
Bouncing Floors: Floors that feel bouncy or unstable, especially in areas near walls or corners, can be a sign that the foundation is not providing proper support.
3. Jammed Doors & Sticking Windows
Difficulty Opening or Closing Doors and Windows: If doors or windows start to stick or fail to close properly, this could indicate that the house is shifting or settling, causing misalignment of door frames or window frames.
Gaps Around Doors/Windows: If gaps develop around doors or windows (for example, at the top or bottom), it can also signal that the foundation is moving, which may require underpinning.
4. Cracking or Bowing Walls
Bowing Walls: If interior or exterior walls start bowing, bulging, or leaning, this could suggest that the foundation is not providing enough support, especially in cases of moisture-related expansion or soil instability.
Severe Wall Cracks: If the cracks are large and running horizontally across walls, this is often a serious sign of foundation instability, indicating the need for underpinning.
5. Gaps Between Walls and Ceilings or Floors
Separation Between Walls and Ceiling/Floor: If there is noticeable separation between walls and the ceiling or floor, it may indicate that the foundation is shifting or settling unevenly, which could require underpinning to stabilise the structure.
6. Sinking or Settling of the Structure
Uneven Settlement: If different parts of the house are sinking or settling at different rates, it can cause the structure to become unlevel and may be a sign of foundation issues.
Visible Foundation Movement: You may notice that the foundation itself has settled, cracked, or shifted, which can be a clear indication that underpinning is necessary to restore stability.
7. Water Damage or Drainage Issues
Water Pooling Around the Foundation: If water is pooling around the foundation or basement, it could indicate that the soil is moving or shifting, which can weaken the foundation and may lead to further settling. Proper drainage and underpinning may be needed.
Flooding or Dampness in the Basement: Excessive moisture in basements, whether from leaking pipes or poor drainage, can cause soil erosion around the foundation, resulting in structural problems that may need underpinning to address.
8. Foundation Settling Due to Soil Issues
Expansive Soils: If the foundation is built on expansive soils (clay soils that expand when wet and shrink when dry), these can cause significant foundation movement. If the soil under the foundation is unstable, underpinning may be required to prevent further damage.
Erosion or Soil Compaction: Soil erosion or inadequate compaction during construction can lead to uneven settling of the foundation. If the foundation is no longer resting on solid soil, underpinning may be necessary to provide stability.
9. Cracks in Exterior Features
Cracks in Brickwork or Masonry: Cracks in the exterior brickwork, especially vertical or diagonal cracks, can be a sign that the foundation is shifting, requiring underpinning to prevent further structural damage.
Misalignment of Exterior Elements: If exterior elements like chimneys, porches, or patios begin to lean, shift, or crack, it may indicate foundation issues that underpinning can address.
10. Soil Settlement or Foundation Inspection Reports
Professional Foundation Inspection: If a structural engineer or foundation expert has examined your home and recommended underpinning, this is a clear sign that action is required
Soil Movement: If there is evidence of soil settlement in the surrounding area (such as soil erosion, soil shrinkage, or noticeable soil displacement), underpinning may be necessary to ensure the foundation remains stable.
What are the different types of underpinning?
There are several methods of underpinning, each suited to different types of foundation problems, soil conditions, and the overall structure of the building.
The main types of underpinning are designed to strengthen a foundation, usually by extending or deepening it to more stable soil layers.
1. Mass Concrete Underpinning
2. Beam and Base Underpinning
3. Mini-Piled Underpinning
4. Screw Pile Underpinning
5. Underpinning Using Concrete Pilings
6. Resin Injection Underpinning (Chemical Injection)
7. Jet Grouting Underpinning
8. Pile and Slab Underpinning
9. Underpinning by Structural Slab Extension
What are the alternatives to underpinning a house?
The main alternatives to traditional underpinning are resin injection and screw piles.
Resin injection strengthens the soil beneath the footing by compacting the ground. Screw piles extend the footings to a deeper layer of soil.
What is the cheapest method of underpinning a foundation?
The cost to underpin a footing can vary significantly, and depends on the method adopted, soil condition, accessibility to the failed footing and proximity of other buildings and pavements to the work area.
Traditional underpinning is labour intensive and involves large excavations, so its price does depend on how busy the contractor is. Resin Injection and screw piling have more stable prices.
How long does it take to underpin a house?
Traditional underpinning required digging holes next to the footing and then filling them with concrete.
The excavation of the holes can take some time and will impact gardens and paths as they will be removed.
Traditional underpinning could take a few days for a single underpin to several weeks.
How long does underpinning last?
Concrete underpins, if well-constructed using sound concrete, should last more than 50 years.
Is resin injection as good as underpinning?
Resin injection is different to underpinning.
Resin injection involves strengthening the ground beneath the footing, whereas underpinning involves extending the footing to a deeper layer of soil.
What are the dangers of underpinning?
There are several pitfalls when using concrete underpins.
In reactive clay soils: If only part of the footing is underpinned then there will be differential seasonal movement between the underpinned sections of the footing and the rest of the footings.
This difference in seasonal movement will result in large cracks forming in the walls adjacent to the areas that have been underpinned.
Another problem that arises with traditional underpinning is that poorly compacted soil adjacent to the underpin acts as a water path to the underside of the underpin, which undermines the underpin.
