How trees impact ground conditions and building foundations

Garden bushes, tree and green grass lawn covered with water due to snow melting thaw and flash high water at spring. Natural disaster deluge flooded house backyard pathway ang greenery at countryside.

There is no denying that trees are a beneficial asset to the environment, our lifestyle and a symbol of a healthy landscape. They create shade and privacy, contribute to better air quality, provide habitats for native birds and animals, and help to reduce salinity and soil erosion.

However, without proper consideration and monitoring, trees can also impact our built environment by causing damage to buildings, paths, driveways, and underground infrastructure.

A tree’s influence starts, literally, at the roots; they are responsible for keeping the tree alive by drawing essential nutrients and water from its surroundings. The roots will continue to grow as a tree matures and during this growth, the roots will extend towards anything that will maintain the tree’s life. Roots typically seek out moist soil and will often find entry into old or damaged pipes including stormwater drains, sewage pipes and water mains.

Seasonal change also influences how trees interact with the built environment. During the warmer months of spring and summer, soils can dry out with the lack of moisture causing reactive clays to shrink. In extreme cases, shrinking soil can lead to significant ground movement, subsidence and foundation settlement across the home. Unfortunately, trees can exacerbate this process. In their hunt for moisture, root systems will extend through dried soil, desiccating the ground and absorbing remaining water from the already dry earth.

The combination of dry soil and thirsty tree roots is the perfect recipe for ground movement, and the appearance of worrying subsidence symptoms, including cracks in brick walls, distorted timber frames, and doors and windows that jam. Examples of different causes of subsidence around the home, including those triggered by tree roots, can be viewed on Mainmark’s interactive house: Understanding the cause of problems is essential before a viable solution can be found.

Assessing the influence of trees

There are several factors to consider when determining whether trees could be the ‘root cause’ of damage to a home. These include:


When trees are planted closely together, they are forced to compete for moisture and nutrients in the same area of soil. The larger the group of trees, the greater the impact on soil drying out in the surrounding area. It is therefore more likely for homes or buildings located near large groups of trees to experience effects of adverse ground conditions as the trees absorb more moisture which can contribute to greater ground movement.

Tree types

Tree activity varies across the year depending on its type, so it’s important to identify the trees that are growing near your home. Deciduous trees, for example, hibernate in winter and re-grow in spring. This lifecycle means their water demand is often highest during drier months, which has the effect of increasing the magnitude of soil shrinkage.


A tree’s physical characteristics can determine how much moisture its root system is likely to absorb, but it’s not always just in relation to its overall size. Research into a tree’s influence on ground conditions has indicated that it is the leaf area of the tree rather than its height that ultimately determines its moisture demand[1]. Therefore, thick or tall trees aren’t always the culprit for dry soil; it’s the amount of foliage that can indicate how much water a tree needs to sustain itself.

Surrounding environment

Roads, footpaths, and larger scale developments with limited green space can also prevent moisture from reaching the soil underneath. This lack of permeability can cause dry soil conditions and may force tree roots to draw on the limited moisture available, intensifying soil shrinkage and ground movement. This is common in urban areas where trees are planted for aesthetic or ‘greenscaping’ purposes, without considering the degree of exposed soil and abundance of moisture.

The risk of roots affecting the structural integrity of your property should not be a barrier to planting trees or moving to an area where trees are in abundance. Understanding tree behaviours and their relationship with the surrounding environment can help to manage their influence and reduce the likelihood of damage to the home or a commercial premises.


By James O’Grady

James O’Grady is a Sales and Business Development Manager at Mainmark. He is a civil engineer with 25 years’ experience in structural engineering, construction materials and ground treatment.

“Gender should be irrelevant” Mainmark’s Pip Buunk talks ‘Women in Trades’

Mainmark technicians working on Metro Sports facility in Christchurch

As we continue to work towards shifting the disparity in male or female dominated professions, we look with admiration at individuals who are determined to overcome gender barriers to pursue their passion.

One such individual is Pip Buunk, who is a senior technician at Mainmark in New Zealand and boasts more than 15 years’ experience in geotechnical drilling. Before joining Mainmark, Pip spent much of her early trade career as the only on-site female and New Zealand’s only registered female driller. Throughout her working life, she has managed drill rigs for geotechnical site investigation, water boring and geohazard stabilisation projects.

Pip has experience in a wide range of skills including welding and steel preparation techniques, truck and Moxy driving, operating drilling rigs and geotechnical testing equipment, crane operations, concrete installation and surveying. During her time at Mainmark, she has been able to add resin and grout application for ground remediation and structure re-levelling to her already long list of skills.

Ahead of her appearance at the Women in Trades’ (WIT) ‘Get Into Trades’ event 2021, an annual conference dedicated to educating and encouraging women about careers in the trade sector, Pip shared her advice for job seekers and employers.

Employers need to accept that diversity can be beneficial

Despite her success, Pip is all too aware that there are several barriers that still hold many women back from pursuing careers that have traditionally been dominated by male workers in New Zealand and across the world.

“There is still a handful of the older generation around who aren’t willing to change with the times and accept that diversity can be beneficial; not just to companies but also to industry as a whole. In short, finding an employer willing to take on women,” she said.

“Women are also not being exposed to resources and information on trade career opportunities. Trades have been traditionally marketed to males, especially at the secondary school level. It’s only really become an option marketed to women in more recent years.”

“There is also a general lack of available support for women in the workplace, for example flexibility for those who have children, adequate hygiene facilities and difficulty obtaining PPE with sizing suited to women.”

There has never been a better time for women to choose a trade career

Pip also points out that aside from the active barriers, there are several passive barriers like stereotypes and misconceptions that make women inwardly feel like pursuing a trade is a nonstarter. “Some common misconceptions about women in trades that I have noticed is that you have to be super strong, or that you can’t be feminine in the workplace,” she said.

“The fact is none of this is the case! Firstly, you don’t need to be overly strong, instead you just need to develop safe lifting techniques. Secondly, I’ve also been known to wear makeup because I like it, and I know many others who do too. Finally, if you show up willing to learn, be yourself and put in the work, you’re on the right track.”

Despite the reality of existing barriers and misconceptions, Pip is quick to highlight that there is hope. Dated perceptions of female capability in a trade-based workplace are eroding, and as more employers and companies get on board with gender diversity and inclusion, there has never been a better time to challenge norms and chase your passions.

Companies like Mainmark, for example, recognise that skills and work ethic are not exclusive to gender or specific backgrounds. It is why Mainmark’s employment ethos is driven by diversity and inclusion, and not outdated assumptions about an individual’s capability.

“I feel that the biggest opportunities currently stem from inclusivity and diversity coming to the forefront of many organisations’ goals and plans for the future. It is now a better time than ever to get into a trade career,” Pip said. “Whether you’re a school leaver who isn’t keen on university, or in a corporate career and feel the need for a change, there are endless opportunities out there and growing support from governments to get people into skilled trade apprenticeships and careers.”

“It’s important to figure out what you like doing, what trades might involve those interests, and take it from there. Industry training organisations have a wealth of knowledge regarding skill applications across different trades, so talking to local industry advisors is a good place to start. Work experience is a great way to try out something new and see if it’s a good fit, too. There are many employers who welcome someone who wants to give it a go. You could be like me and have a few weeks school holiday work experience turn into a career!”

Women can approach the job from a different perspective

If Pip could share one message to women interested in pursuing a trade, it would be to stop believing jobs have a gender.

“Everyone brings different experiences and ways of approaching a task or challenge, and we all learn in different ways and at different rates,” she said. “I still come across people who hold the view that trades are simply a steppingstone to a management career and not a complete career option, that they are not appropriate for women who want to have children, or even that trades are a second-rate career choice and lesser than other choices. All of these are fundamentally untrue.”

“Of course, not every trade is suited to every individual, but gender should be irrelevant when it comes to getting into it and getting the work done. It’s ok to try a few different trades before finding the right fit. The basics apply to everyone: show up and put in the work.”

At Mainmark, we are pleased to be supporting the Women In Trades event and believe that fostering a culture of diversity and inclusion brings a unique dynamic to the industry in which we operate.

By Claire Hartley

Claire is a strategic senior marketing and communications professional who joined Mainmark in 2015. She has extensive experience gained in a range of organisations across the APAC region and the UK; from large multinationals and start-ups to industrial B2B, IT and online businesses.

Solutions to help maintain and remediate seawalls

Mainmark technicians injecting and measuring on Bunbury seawall

Australia and New Zealand are surrounded by the sea with coastal living, seaside views and access to water all playing a big part in our way of life. However, when the ocean or an open body of water intrudes too close to urban environments, seawalls are valuable assets for protecting low lying waterfront infrastructure, addressing safety hazards or overcoming access constraints.

While seawalls are often built in coastal or bayside areas, providing protection against large open waters, they can also be found along riverside or lakeside areas where erosion can have a negative impact on urban environments or restrict the enjoyment of recreational activities.

Typically made from steel, rock, or concrete, seawalls are constructed to suit the landscape and water conditions. Vertical seawalls, for example, are sturdy walls that block waves from ocean-facing coastlines while sloped seawalls, or revetments, are designed to dissipate the energy from smaller waves to lower the risk of erosion.

Left unprotected, natural foreshores can be at risk of flooding and weakened ground conditions, which can put waterfront structures in danger of collapse. This was the case at a Gold Coast waterfront property where canal water washed away fine sandy soil behind a revetment wall, causing the property’s footpath and retaining wall to subside and become unsafe.

The effect of deteriorating seawalls

While seawalls are engineered to withstand marine environments and extreme weather, old or poorly constructed seawalls can be hazardous to people, structures and the surrounding environment. A deteriorating seawall can cause waterfront infrastructure to subside, resulting in cracks that can lead to water ingress behind the seawall. This was seen in Sydney, where a historic sandstone seawall, protecting a waterfront apartment on Sydney Harbour, had started to deteriorate as a result of years of tidal currents and water movement. Without proper remediation, the wall would have continued to degrade until it could no longer support the apartment’s patio or the apartment block itself, which would be at risk of collapsing into the harbour.

Entire strips of tourist-attracting waterfront development may also be affected by old or deteriorating seawall infrastructure. Without suitable protection from waves and tides, or a long-term plan to mitigate the ongoing effects of water movement, structures may become unsafe, uninhabitable, and unviable for tourist operators and other businesses who rely on the location’s access and safety.

An example of this was the ongoing subsidence threatening the structural integrity of the stone walls protecting the banks of Lake Burley Griffin, a large artificial lake in the heart of Canberra that is a popular destination for locals and tourists. Mainmark was engaged by the National Capital Authority (NCA) to repair, strengthen and renew the stone wall and surrounding footpaths as part of a three-year lake wall renewal program. Mainmark’s Teretek resin injection was used to consolidate the soils, fill voids and re-stabilise the wall, as well as re-level the surrounding pathways and adjoining grasslands.

What is the solution?

A properly designed seawall is built to stand the test of time and when newly constructed, should last for many decades. However, due to constant contact with water that may be flowing or contain corrosives such as salt, seawalls should be regularly monitored and maintained for signs of deterioration. If sections of the wall are damaged, its footings have eroded, or the soil behind the wall is weakened, the wall may need to be reconstructed or reinforced.

Using tailored solutions that provide long-term stabilisation is key to revitalising ageing or deteriorating seawalls. This was a lesson that the City of Bunbury learnt when they discovered damage to the seawall protecting the Marlston waterfront entertainment precinct. Prolonged exposure to waves and tidal movements had allowed water to penetrate through the wall and under the foundations. A section of the wall had subsided and a large crack had formed in the face of the wall. There was real concern that the wall may collapse. The City of Bunbury carried out emergency grouting on the worst affected area, but it proved to be very expensive. Mainmark worked with the city’s engineers to develop an innovative and cost-effective solution for the entire wall repair.  Mainmark’s Teretek engineered resin proved to be an ideal solution to strengthen the wall by densifying the soil and filling voids where sand had been washed out due to the tidal movement.

As urban development continues to increase, seawalls will remain crucial elements for protecting water frontages. When constructing seawalls, an asset remediation plan should be considered to help address issues that may arise over time, should sections of the wall start to deteriorate due to ground or water conditions.

Mainmark has extensive experience remediating seawalls, including revetments, using a range of proprietary cost-effective solutions that can protect the asset’s longevity and structural integrity without any detrimental effects on the environment.

While seawalls are engineered to withstand the forces of water, to function properly they must be well built and maintained. Using the right materials and reinforcement measures, a structurally sound seawall will allow communities to safely enjoy the waterfront lifestyle for which Australia and New Zealand are famous.

By Steve Piscetek

Steve Piscetek is Mainmark’s Divisional Manager, MCM (Mainmark Civil and Mining). Steve has extensive experience working in construction, road and water infrastructure, the mining and resources sector and offshore construction. At Mainmark, his technical acumen and pragmatic approach to safety and quality assurance has seen him successfully tackle many challenging and complex ground remediation projects.

Regional spotlight series: assessing the geological landscape in Queensland, Australia

Aerial view of Surfers Paradise on Queensland's Gold Coast

Following our recent regional blog that looked at the different ground conditions in New Zealand, we now turn our attention to Queensland, Australia’s second largest state with a total area of 1,852,642 square kilometres, known for its diverse natural environment and extreme weather patterns.

Mainmark services Queensland with a dedicated team based in Brisbane, the Gold Coast and Sunshine Coast, and in Northern Queensland, with expertise in the residential, commercial, civil infrastructure and mining sectors.

While each region has its own unique challenges, Mainmark leverages its collective local expertise and skillsets to provide a range of specialised bespoke ground engineering solutions for customers, tailored to their specific needs.

Surf, sand and the impact of high-rise development

Queensland is affectionately known as the ‘sunshine state’ with the Gold Coast and Sunshine Coast offering a quintessential coastal lifestyle that appeals to home buyers and property developers alike.

The Gold Coast is renowned for its large-scale high-rise developments that are prevalent along the main beachside strip with old houses, originally constructed in the 60s and 70s, being knocked down to make way for multi-storey apartment buildings – some as high as 30 storeys or more. These sites often require deep excavation for basements and underground carparks, however, excavation within these tightly confined spaces can weaken surrounding soils and cause subsidence issues for neighbouring houses and apartment buildings, especially those built to the boundary.

Sites with unstable sandy and non-cohesive soils can be addressed either during or after construction using solutions such as Mainmark’s Permeation Grouting, a widely used low pressure grouting technique that can be used to support excavation, shore up adjacent structures where unstable ground may be a safety hazard, or provide additional ground bearing capacity to accommodate the increased load of a new structure.

While engineers may consider conventional piling and jacking techniques to re-level subsided buildings, these processes require the use of large heavy machinery. Site access is becoming increasingly problematic due to the Gold Coast’s urban density which has made piling an expensive and time consuming option. However, Mainmark’s advanced range of proprietary grout and chemical injection solutions, such as JOG Computer-Controlled Grouting and Teretek® resin injection, can be smart solutions for high rise residential and commercial buildings as cost effective, non-intrusive alternatives to traditional piling.

Building on reclaimed land and low lying flood plains

Poorly compacted land is also a growing concern for homes and businesses built on reclaimed land in the low lying marshy flood plains of South East Queensland where it is not uncommon for a 20m layer of soft, highly compressible soil to extend down from the surface. This issue can also create problems for commercial sites such as transport yards where the movement of heavy vehicles and shipping containers can put pressure on the ground beneath driveways and hardstands, causing subsidence. This was the case at South East Queensland Hauliers (SEQH), a wharf logistics business that was built on reclaimed mangroves. The company’s concrete hardstand area was ‘dishing’ in the middle due to water ingress from the high water table. The company engaged Mainmark to help improve the ground beneath the hardstand and re-level the concrete slab using JOG Computer-Controlled Grouting.

As population migration to the sunshine state grows, so too has the number of wetlands and agricultural farms, such as cane farms located near the Gold Coast, that have been developed into residential housing estates. While building on reclaimed land can bring enormous economic benefit to local regions, the construction process often requires ground improvement modifications prior to building to ensure the ground is suitable for construction. Failure to undertake appropriate ground improvement measures prior to construction can result in serious issues, leaving homes at risk of differential settlement. Mainmark has helped remediate numerous homes built on reclaimed land, including a single storey brick residence in Warner, Queensland where the property’s concrete floor had dropped up to 120mm. Mainmark was able to successfully re-level the floor using Teretek.

The effects of wild weather in tropical North Queensland

As Queensland is a predominantly tropical state, the region is prone to extreme weather conditions which can cause havoc on building foundations. The issue is largely due to the prevalence of clay soils which swell during wet weather and shrink during extended dry conditions such as drought.

In some Queensland areas, the state’s tropical wet weather can cause soils to swell and shrink by up to 70mm throughout the year with Mainmark receiving many enquiries from homeowners worried about cracks that have appeared in the walls of their home as a result of such movement. The constant ground shift can cause serious cracking and structural damage with cracks becoming bigger and more pronounced the longer the dry spell continues.

Extreme weather not only affects homes but also infrastructure, particularly in North Queensland where Mainmark has seen an increase in demand for remediation work on culverts and bridges that have been damaged due to torrential rainfall. Underground culverts are vital for North Queensland’s road network as they allow the flow of flood water and runoff, however, sometimes the infrastructure struggles to cope during heavy rain events as water gradually compromises the culvert lining and causes voids to form around the culvert as surrounding soil is washed away. This was the case on a North Queensland windfarm, when two culverts located beneath an access road and an embankment were seriously damaged during a tropical cyclone. Mainmark was able to successfully restore the culverts’ structural integrity by injecting the area surrounding the culverts with Teretek engineered resin.

Mainmark’s team addresses the geotechnical challenges of Queensland’s diverse geography, extreme weather and high density development by thoroughly assessing the underlying ground conditions to understand what is achievable. With more than 25 years’ experience and intimate knowledge across the Queensland region, our highly skilled engineers and technicians assist homeowners, engineers and civil contractors to address a range of ground problems with innovative, state-of-the-art ground engineering solutions and methodologies that are non-invasive, efficient, cost-effective and environmentally inert.

Dolan NilsonBy Dolan Nilson

Dolan Nilson is Technical Sales Manager at Mainmark Ground Engineering. Dolan is a qualified engineer who has previously worked in the petroleum, oil and gas industries in Scotland, Texas, Indonesia and Malaysia. At Mainmark, he has assisted on a range of complex ground improvement projects in the civil and mining sectors, including re-levelling large structures, remediating ageing infrastructure, and culvert and pipeline abandonment.

Understanding foundations – what you need to know to keep your building structurally sound

waffle foundations

The integrity and longevity of any built structure starts from the ground up, which is why it is often said that a building is only as good as the foundations it is built on. However, different types of foundations are used for different buildings, generally determined by the site’s geological factors, the type of building, and the era in which it was constructed. Importantly, the type of foundation will impact the remediation approach taken should the structure’s stability ever be compromised.

Foundations are more than simply a solid base which a building sits upon. They are a vital element of construction that carries the structural load bearing and weight distribution of a building’s walls, columns and other structural elements.

Factors that influence what type of foundation is best suited to a site are numerous. This can include the weight or scale of the building, drainage requirements and water table, site topography including site slope, construction budget, the type of building materials available, soil composition (geology), local climate, local wind conditions and seismic considerations.

Soil is of particular concern as foundations must be fit for purpose and adaptable to a site’s conditions, which can range from stable, non-reactive rock with no moisture-based ground movement, to highly reactive clay sites that experience significant ground movement following changes in moisture levels. Some sites may be in highly desirable areas with unmissable real estate opportunities but present challenging ground conditions, the building is more likely to be affected by factors such as moisture conditions, reactive soils, landslips, sink holes and voids.

Foundation 101

Whether building, renovating or remediating a property, understanding the different types of foundations will help determine the best path forward. Foundations are broadly classified as ‘shallow’ or ‘deep’ and are differentiated by the depth beneath the ground’s surface. Shallow foundations are placed closer to the surface and are suitable for stable conditions where ground movement is less likely, while deep foundations are recommended for structures that are being built on sites with reactive ground conditions. Deeper foundations mitigate against the impact of seasonal moisture variation and tree root intrusion.

Waffle Raft-Slab foundations are perhaps the most common in modern buildings and are an inexpensive foundation type as the foundation requires minimal excavation. Waffle slabs, also known as waffle pods, are a reinforced concrete footing and slab system created with concrete that is poured around polystyrene forms that sit on top of the soil.

Raft foundations are a type of shallow foundation within the slab family. Usually used as the foundation for new houses and extensions, raft foundations are applied as a solid continuous base across the entire building. They help to evenly distribute weight carried by walls and columns, allowing for loads to be supported by edge and internal beams. The depth and spacing of these beams is determined by the ground reactivity, the construction type and the degree of articulation in the building envelope. Raft foundations are preferred in areas where soil is highly susceptible to moisture changes because of climate and composition.

Strip foundations, or strip footings, form a continuous, linear line of support underneath walls. Strip footings are placed within a shallow trench and reinforced with steel. These footings are popular in Australia and are preferred for light loads, like the interior or exterior walls found in residential properties. The material of the strip footing is typically determined by the construction of the time. Prior to the late 1800s, most strip footings were made of stone. The stone could be dressed blocks or natural stone. From the late 1800s to the early 1900s, bricks were the predominant strip footing type. With increased availability of ready-mix concrete, concrete strip footings replaced brick strip footings from the 1930s. Strip foundation structures are used in combination with stump footings for the internal load bearing.

Stumps, referred to as a pile footing in New Zealand, are the simplest and most familiar systems used for the vertical support and transfer of building loads to the foundation. Stumps are used to support timber-framed houses for which they are typically the most cost effective. The stumps are made from timber, concrete or steel and must have a concrete or timber footing placed underneath the base of the stump.

Pile foundations are a type of deep foundation that comprise of pillars – or ‘piles’ – that provide support for a building by being placed deep into the ground. Pile foundations are preferred when the soil conditions near the surface are too soft or reactive. Such soil conditions can cause loads to shift, making slabs and other shallow foundations less effective. However, pile foundations can prevent differential settlement of foundations by transferring the weight of a building through its columns to a stiffer, deeper soil strata.


Foundations are often subject to the surrounding ground conditions, which may change due to changing climate, minor seismic activity or urban influence such as digging, plumbing and tunnelling. Over time, foundations may need maintenance to overcome these factors and continue to perform their design function. In such events, Mainmark can provide guidance and solutions to help re-support foundations to benefit structural performance. For example, Mainmark helped a heritage building in Sydney increase its foundation’s load bearing capacity from 140kPa strength to 200kPa using its Teretek® resin injection solution, which improved and consolidated the soils, preventing the risk of future settlement. In New Zealand, Mainmark used Terefirm® Resin Injection to strengthen the ground and re-level the foundations beneath the Northwood Supa Centa in Christchurch after the shopping centre experienced liquefaction induced ground deformations following the Christchurch earthquakes in 2010 and 2011.

Understanding the characteristics of the different foundations types will put you in the best position to help ensure your building, regardless of its age, location or site conditions, has the ability to stand the test of time.

By Max Kudrenko – Technical Manager

Max Kudrenko is the Technical Manager(Vic/Tas) at Mainmark Ground Engineering. Max is a civil engineer who has experience working with different grout, resin and other cementitious geotechnical and ground improvement technologies in the residential, commercial, gas/oil and civil sectors. He has successfully project managed works throughout Australia, New Zealand and Japan.

Regional spotlight series: how geological considerations differ in Auckland, Wellington and Christchurch, New Zealand

Auckland city skyline Waitemata harbour New Zealand

When it comes to ground engineering, topography and geological conditions will often impact the built environment. The ground conditions will also inform the remediation approach Mainmark uses for different projects. With a global footprint spanning from Australia and New Zealand to Japan and the United Kingdom, Mainmark has considerable experience working in different regions, many with complex issues specific to local areas.

In the first of our regional spotlight series, Mike Baker, Area Manager in NZ, takes a closer look at ground conditions in New Zealand, in particular those in the three major hubs of Auckland, Wellington and Christchurch. We delve into the unique ground engineering challenges in each city, and some of the solutions that Mainmark frequently uses to address the varying issues, often impacted by local soil conditions.

While each region has unique challenges, Mainmark’s approach is not simply about quick fixes. Instead, we look closely at the site and apply tailored ground improvement solutions that can address the underlying cause of the problem.

In New Zealand, the complex weather patterns range from subtropical conditions in the North Island to a cooler alpine climate in the South Island. Often referred to as the ‘Shaky Isles’, New Zealand is also an earthquake-prone region due to the number of fault lines running almost the entire length of the country.

Here, we take a closer look at the geotechnical considerations in New Zealand’s three biggest cities.


Auckland’s climate has two distinct ‘wet’ and ‘dry’ seasons. In summer, New Zealand’s largest city experiences subtropical conditions, compared to the rest of the country, which enjoys a more temperate climate. With the prevalence of reactive clay soils, weather and seasonal shifts can play havoc on Auckland’s buildings due to the ‘shrink and swell’ effect that sees soils expand when it gets wet in the winter and shrink back in the summer when it dries out. Visible cracking may appear in the ground’s parched surfaces, and these weakened soils may cause a home’s foundations to ‘sink’.

This ground reaction is something that property owners in Auckland need to consider when cracks appear in the walls of their home. The Mainmark team has seen a number of structural problems stemming from subsidence – the propensity for upward, lateral, or downward ground movement which can result in structures moving – including cracks forming in walls, and windows and doors failing to open or close properly. If subsidence worsens, larger cracks in the home’s brickwork can form, visible both inside and outside the home, and the sinking foundations might also lead to floors becoming unlevel. These signs of subsidence can become serious and very costly if left untreated.

Recent drought conditions in the Auckland area have led to drier than usual ground conditions. Mainmark’s Auckland team has received an increasing number of calls from concerned homeowners wanting to rectify problems relating to subsidence. In many of these cases, Teretek® engineered resin injection solution is used to help to raise and re-level sunken homes, both cost-effectively and non-invasively.


New Zealand’s capital, Wellington, sits on the southernmost point of the North Island. The city is regularly shaken by small and medium-sized earthquakes due to the Wellington region being crossed by a number of major faults, including the Wairarapa, Wellington and Ohariu faults. Wellington currently experiences minor seismic activity every few months, but these tremors have not been a significant threat to homes or lives. However, the ongoing study of these fault lines has prompted concern from scientists that a large earthquake may occur in the future, like the 7.5 magnitude 2016 Kaikōura earthquake which left Wellington with cracked buildings, windows smashed and without power in several areas. This seismic activity has prompted an increased awareness of the hazard and Mainmark has undertaken several ground resilience and liquefaction mitigation projects in the area since.

As the country’s administrative centre, Wellington is home to many government agencies and departments that have received investment for building upgrades and structural reinforcement to help protect these buildings from the effects of a future earthquake. For example, in 2019, the Mainmark team undertook a very large ground strengthening project for the Seaview Wastewater Treatment Plant, using Mainmark’s proprietary Terefirm® Resin Injection technique to densify the soils and increase its New Building Standard (NBS) rating to ensure the facility can continue operating following an earthquake.

While ground improvement projects are increasing in Wellington, the area’s ground conditions consist largely of soft sand and silt with clays and gravels sometimes present. One of the key challenges for new home builds is that many buyers are unaware of the potential long term foundational implications that can affect homes built on soft ground. The ground must be adequately prepared which may include a site excavation to remove the soft soils before laying the foundation. This type of foundation, where a more stable layer of material is placed beneath the foundation, is known as a gravel raft and provides greater foundation support prior to pouring the slab for a new home. Mainmark’s Terefil® is also a great alternative to gravel rafts as the lightweight cementitious fill creates a stable slab that helps protect structures against liquefaction and future subsidence. The solution was used for a four-unit complex in Christchurch and an electricity substation in Auckland.

Wellington’s topography can also present a challenge to building stability, with many of the city’s houses located on steep hills with critical retaining walls and often no vehicle access. Many older homes, some more than a century, are in desperate need of repair including ground remediation work.


Located on the east coast of New Zealand’s South Island, Christchurch has been an important focus for the Mainmark business following the 2010-2011 earthquakes which caused significant damage to infrastructure and buildings due to liquefaction. Homes, businesses, public buildings and historical monuments either sunk, shifted, or crumbled and many are still awaiting remediation.

Mainmark has played an important role in helping the Christchurch community remediate their properties, including the re-levelling of significant large-scale structures using JOG Computer-Controlled Grouting. In 2013, the company initiated a series of liquefaction mitigation trials using expanding polyurethane resin which was found to be a viable ground strengthening and re-levelling solution for use underneath existing buildings. While it has been 10 years since the earthquakes, Mainmark continues its work in Christchurch by remediating structures affected by earthquake damage and liquefaction. Many building owners are seeking to future proof their buildings to ensure they can withstand the impact of a potential future earthquake. Commercial properties are also required to comply with the Building (Earthquake-prone Buildings) Amendment Act 2016, which identifies high risk buildings that must be structurally remediated.

While much of Mainmark’s work in the South Island has focused on Christchurch, the organisation also services the entire region including Queenstown, a growing trade and tourist hub. Mainmark was recently contracted to remediate O’Connells, the city’s largest indoor shopping centre, helping the building achieve an increased NBS rating, a seismic standard indicator that rates a building’s ability to withstand an earthquake.

New Zealand may be a relatively small geographic area, however each of these three regions presents unique ground engineering and remediation challenges, which the Mainmark team tackles using a range of solutions tailored to the individual site requirements. As a solutions-based business, Mainmark goes to great lengths to understand the individual ground problems of each project, and creates bespoke solutions by working through the process with its customers. With more than 25 years’ experience, Mainmark is continually broadening its capabilities, working across the different geotechnical nuances from one end of the country to the other.

By Mike Baker

Mike Baker is Mainmark New Zealand’s Area Manager in Wellington. After joining Mainmark in 2013, Mike supervised remediation of the modern Christchurch Art Gallery which was shaken by the 2010 and 2011 earthquakes that hit New Zealand’s South Island. In 2019 he led the first of its kind Seaview Wastewater Treatment Plant liquefaction mitigation project in Wellington.

Mainmark is challenging WHS culture for the better

Standard construction safety equipment on wooden table

Wednesday, April 28 marks World Day for Safety and Health at Work and Workers’ Memorial Day. It is a time to reflect on the importance of workplace practices, with the aim of reducing and preventing work-related occupational diseases, deaths, injuries, and illnesses.

Despite a 53 per cent decrease in workplace fatalities between 2007 and 2019[1] in Australia, incidents still occur every year. This is why it’s important to continue raising awareness of work health and safety (WHS) and proactively take action to minimise the risks to employees.

Mainmark remains dedicated to WHS and last year appointed work health safety manager Francesca Davis, whose wealth of industry knowledge and experience supports ongoing safety awareness within our organisation.

Since joining Mainmark in August 2020, what progress have you seen in terms of WHS culture and protocols?

There has been a huge shift in culture in WHS because we are approaching it differently. We now use tools like ‘leader-led’ safety conversations that involve our senior managers talking proactively to staff across the entire business about safety issues that directly relate to their role.

Initially, I would brief the whole ANZ team on a WHS policy or specific procedures that they would then have to remember and follow. Now we actively discuss details about different safety issues and talk collaboratively about what solutions are available.

This approach has created a huge cultural change – rather than simply providing a work-around for an expected situation, we’re acknowledging the solution itself and exploring its merit in the workplace.

Has there been a reduction in reported incidents at Mainmark?

Incident reports are based on what is reported after an incident occurs, and are therefore not always an accurate or appropriate measure. Talking about incidents in a statistical context doesn’t always help our team recognise and act on risks and hazards. Instead, we prefer to focus on the indications of a healthy WHS culture. We discuss how many in our team are having open, honest conversations about safety concerns, and we ask if people are sharing their lessons learned, or including safety in their daily ‘toolbox talk’.

We also focus on whether or not business leaders are actively engaging in conversations with their team about safety issues to ensure there is no gap in understanding between management and the wider workforce. This helps ensure that any emerging safety concerns are addressed and the chance of future similar incidents is minimised.

What WHS behavioural changes have either happened or need to happen at Mainmark?

What we’re focusing on is subscribing to a safety culture based on the idea that our people are at the core of safety in Mainmark, rather than processes and procedures.

Workplace safety has traditionally been about procedural awareness; making sure people follow the procedure and do not deviate from the steps in place. However, the fact is that our team members come across unexpected situations every day, and they need to know how to resolve a situation and come to a safe solution in the heat of the moment. Mainmark’s WHS approach does include a procedure, however that procedure is more of a foundation that we stand on as we concentrate on risk awareness.

Our WHS behavioural changes are a result of acknowledging that good WHS is not about knowing policy verbatim; it’s about empowering someone to understand risk management and focus on the everyday problems that may appear on site. It’s about ‘on the fly’ risk assessment and understanding your actions, possible consequences, and being able to appropriately resolve issues on site in safe ways.

Ultimately, Mainmark has prioritised safety awareness and good judgement over a rule book, so people have the internal thought processes necessary to assess risk and make good decisions to safeguard themselves and others.

Can you talk about the outcomes or feedback from your recent initiatives?

Our ‘Drive so we all survive’ campaign was very successful. We helped reduce incidents of speeding and unsafe driving month on month by 50 per cent. We partnered with PBF Australia (The Paraplegic Benefit Fund) who delivered a series of inspirational talks aimed at injury prevention. These talks were delivered by a spinal cord injury survivor and challenged the Mainmark team to consider the lifelong impacts an unsafe work choice can have.

We capitalised on an already existing Verizon GPS tracking system for our light and heavy vehicles to implement real-time coaching and speeding alerts.  We implemented recognition and rewards to promote safe driving behaviours across the business, taking time every week to acknowledge these staff members. It empowered us to believe that a positive WHS culture can actually have an impact on the success of the business, so it’s worth investing time and money into it.

Under your lead, are there any safety protocols or issues that you’re spearheading that are specific to Mainmark?

Mainmark is utilising its growing shift in WHS culture to improve ‘chain of responsibility’ awareness, and applying this to our company vehicles. We are revising who in the organisation is responsible and can address a variety of vehicle related safety factors, including fatigue management, driver responsibility, rostering, fleet maintenance and other transport elements.

This move is in response to the national heavy vehicle law in Australia, which previously held a heavy vehicle driver responsible for an accident where their vehicle was involved. It was realised that the driver is actually at the end of the chain of responsibility, which includes those involved with vehicle maintenance, managers and other roles that have a major hand in how the driver does their job.

Ultimately, WHS is a fundamental principle and an ethical responsibility – we don’t just do it to tick a box; we do it protect the Mainmark family.

[1] Safework Australia, 2020, Key Work Health and Safety Statistics, Australia 2020.

Francesca Davis

Francesca is an experienced Work Health Safety Manager with a demonstrated history of working in the construction industry. Skilled in Rail Safety, Risk Management, Safety Assurance, Subcontracts Management, Project Estimation, Workplace Safety, and Occupational Health.

10 years of engineering development after the 2011 Christchurch earthquake

Mainmark technician testing earthquake liquefaction mitigation

Even though 10 years have passed, it seems like only yesterday that New Zealand experienced the 6.3 magnitude earthquake that shook the foundations of Christchurch’s central business district on Tuesday 22 February 2011.

The catastrophic event claimed the lives of 185 people and caused widespread destruction, coming less than six months after a 7.1 quake shook the South Island in September 2010.  While smaller in magnitude than the first, the 2011 quake was unusually ferocious due to its shallow depth and epicentre being closer to the city. Following the state of emergency response and the immediate remediation of critical infrastructure and buildings had been addressed, Christchurch turned its attention to the future and how it could minimise, or even prevent, that kind of destruction in the future.

Earthquake and geotechnical engineering has evolved significantly since the Christchurch earthquakes and Mainmark has been leading the way forward. A lot has been learned about the relationship between existing structures and geotechnical profiles, as it was discovered that liquefaction contributed heavily to the overall level of destruction.

Christchurch has an abundance of aquifers and low-lying land near the coastline, resulting in relatively high groundwater[1]. Both earthquakes resulted in significant land deformation and surface manifestation of liquefaction that required a colossal effort from volunteers who worked tirelessly for several months to clear affected areas of silt and sand . The foundations of many residential and commercial buildings, infrastructure and historical sites were unable to handle the large deformations observed, causing structures to sustain significant structural and foundation damage.

10 years of progress

Since the 2011 Christchurch earthquakes, Mainmark has invested heavily in research and development to help remediate damaged, and preserve existing, structures. During the red zone trials Mainmark was able to prove their Terefirm Resin Injection technique to be a viable, non-invasive ground improvement and liquefaction mitiation solution to strengthen weak soil sub-bases and help ensure the ground is less susceptible to liquefaction or lateral spread in the event of a future quake. Mainmark’s Terefirm Resin Injection is designed to densify the soil with an expanding polyurethane resin mix, that helps protect built structures from earthquake damage and resulting liquefaction.

With the help of Nick Traylen from Geotech Consulting, Mainmark conducted peer-reviewed field tests in 2016 and 2017 using its resin injection technology, with the positive outcomes and application published in a report that has been endorsed by the New Zealand Geotechnical Society. These tests were initiated following a prior series of ground improvement trials sponsored by the New Zealand Earthquake Commission (EQC) and the Ministry of Business and Innovation (MBIE) in 2013, where Mainmark’s engineered resins were tested in a series of earthquake simulations through controlled shaking rigs and blast testing.

These tests and trials were only the beginning. As it became clearer that Mainmark’s products and techniques had great potential for liquefaction mitigation and recovery, there have since been many successful projects that have set a benchmark for post-disaster building recovery.

Most notable was the work accomplished for the Christchurch Art Gallery, which had subsided up to 182mm and suffered uneven footings across 6,5000m2 after the 2011 earthquake. After injecting more than a million litres of material under the gallery and re-levelling the entire structure, Mainmark was recognised for setting a new benchmark in earthquake remediation for large scale buildings and was awarded International Project of the Year in 2016 for its efforts.

News of the Christchurch Art Gallery’s successful re-levelling began to spread, and greater awareness of the new techniques that were available to restore the effects of ground movement. Mainmark was also able to apply its specialised approach to re-level residential structures, including a family home in Upper Hutt, and a two-storey home 20 minutes from Christchurch, which had both suffered damage from the earthquake. These projects benefitted from Mainmark’s non-invasive solutions which were successfully completed with little to no excavation or demolition, at significantly less cost compared to more invasive alternatives.

Mainmark has also restored larger structures in Christchurch, including the seven storey West Fitzroy apartment building and the 33,283m2 Northwood Supa Centa. In both cases, the structures had suffered differential settlement as a result of the earthquake and its subsequent aftershocks; the retail centre had settled up to 160mm and the apartment building 135mm. Mainmark used JOG Computer-Controlled Grouting with to-the-millimetre re-levelling precision and engineered resin injection to restore the buildings to pre-settlement levels.

The resulting advancements over the past 10 years have been enormous – rather than remediating earthquake damaged structures using highly invasive concrete piling and underpinning, a viable and proven low-invasive alternative has now been established and has the ability to remediate existing structures using solutions that are applied directly beneath a damaged building. This capability was previously not possible.

The geotechnical learnings from the Chrischurch earthquakes have not only changed engineering approaches to disaster recovery but are also now recognised as a viable solution to improve building and infrastructure resilience in high-risk areas. According to Coffey principal engineering geologist, Nick Clendon, in these 10 years there has been greater consideration around proactive ground improvement and mitigating damage. This was seen when Wellington Water sought to strengthen the ground underneath the Seaview Wastewater Treatment Plant after post-earthquake changes to the Seismic Prone Building Act Amendment 2016. The plant is located near an active seismic fault in New Zealand’s North Island. Wellington Water contracted Mainmark due to Terefirm’s unique ability to be applied under existing structures and increase the facility’s New Building Standard (NBS) rating to 55 per cent, in compliance with requirements for IL4 critical infrastructure.

Looking back on 10 years of geotechnical engineering since the 2011 Christchurch earthquake events, Mainmark has made tremendous strides in improving the safety, stability and longevity of the built environment. With non-invasive, cost effective materials now more readily available, we look forward to further advancements with more exciting innovations and proactive approaches to building remediation and preservation.

Mainmark is a proud sponsor of the New Zealand Geotechnical Symposium (NZGS), 24-26 March, 2021 in Dunedin, New Zealand where geotechnical practitioners will come together to reflect on the lessons learnt over the last 10 years since the Christchurch earthquake.


By Theo Hnat

Theo is business development and technical manager at Mainmark. Based in Christchurch, New Zealand, Theo holds a Bachelor of Engineering (BE) Structural Engineering Honours and is currently undertaking a PhD in Earthquake Engineering.  Theo’s responsibilities at Mainmark include researching new technologies in ground improvement and liquefaction mitigation, structural risk assessment of existing structures, design, and analysis.

Mainmark supports #ChooseToChallenge on International Women’s Day

International Womens Day banner

International Women’s Day on March 8 is a time to recognise women around the world and why it’s important to stand up against gender inequality.

The theme for this year, #ChooseToChallenge, highlights the choices we make as a society and the need to support gender equality. #ChooseToChallenge is based on the idea that we can all help challenge the status quo and advocate for an inclusive world, but this can only happen if we collectively take responsibility for our thoughts and actions.

By choosing to call out gender bias in the workforce, we can prevent stereotyping and encourage diversity. #ChooseToChallenge is a message that Mainmark is proud to support.

Ekaterina Tabbernal, Head of People and Culture at Mainmark, plays an integral role in fostering inclusivity and diversity across the business. Here she shares her experience working with Mainmark and her thoughts on taking on the challenge for change.

As a HR professional, what types of changes do you think are needed for companies to foster greater workplace gender diversity?

I feel we need a mental shift to action gender inclusive agendas. Taking a closer look at how tangible changes like inclusive recruitment, employment opportunity promotion, and remuneration balance can make a difference. There is also a need to invest in educational programs that promote gender diversity and address stereotypes.

Clear diversity and inclusion policies which result in men and women being hired across all roles and levels will breed higher job satisfaction, which in turn increases employee engagement and performance.

From a practical standpoint, communication is key. We should communicate that we have a desire for gender balance and promote that message on social media, in our recruitment process and job advertising.

What positive changes have you seen in today’s culture regarding gender diversity?

I am fortunate that, at Mainmark, male team members are supportive of hiring more female employees. Even though there is more to do in society in this regard, I believe there is growing support from men to make women feel more comfortable in pursuing careers in industries that may have traditionally been male dominated.

Are there any areas in today’s society where you believe more work is needed?

A lot of companies have a diversity and inclusion program, but specific action is often overlooked. Some companies are satisfied with ‘ticking the box’ of having a diversity policy, but simply having a policy doesn’t necessarily translate into outcomes. There are some companies that do a fantastic job, but overall, I think there is still a lot more work to do to translate policies into action, and action into real outcomes.

What would be your advice for women who are interested in working in the industrial sectors but may feel held back by gender bias?

I would say just be brave, be bold and don’t let anything hold you back. I find that when people are knowledgeable and passionate about their work, companies that support gender diversity are eager to capitalise on that.

It can be a daunting experience if women are looking to enter a specific sector that may be predominantly occupied by men, but I say be bold and let your passion shine through.

To continue the momentum for #ChooseToChallenge, what is important to remember to help foster positive gender diversity in the workplace?

I think we need to continue to encourage social accountability. When we see something is not right, we should engage in a conversation about it, and the more we talk about it the healthier the conversation becomes, and the more we see a willingness to change.

Movements like International Women’s Day shouldn’t just be about a once-a-year event. We should challenge ourselves to continue to grow. We want men to support gender equality, but we also need women to have the courage to stand up for what they want and speak out against gender imbalance.

Ekaterina Tabbernal

Head of People and Culture, Ekaterina Tabbernal leads and supports the Human Resources function at Mainmark. During work hours you can find Ekaterina engaging with staff, coaching managers, and creating policies and systems to ensure Mainmark remains HR compliant.

Putting cracks into perspective

Cracked Red Brick Wall

Our homes are typically one of the biggest investments we make in our lives. It therefore stands to reason that the last thing we want to see are cracks in the walls, as they can be an indication of structural damage which can lead to financial strain.

However, cracks have a variety of implications, so it is important to know how to gauge the cause and severity of the cracks in your walls to determine the best course of action.

There are cracks in my walls – how serious is this?

No crack within the home is welcome, but there is a difference between minor hairline cracks that can be patched up with little hassle and larger cracks that may indicate serious structural issues. Shorter or thinner hairline cracks are typically superficial, appearing on the surface of walls and unrelated to the structural condition of the house or its foundations. These cracks can be unsightly but don’t usually point to severe damage and any repairs are largely cosmetic. Larger cracks, however, are often the result of ongoing building movement or external issues that have compromised the house’s structural integrity. The cause of large cracks can be costly to repair and create ramifications for a house’s value and the safety of its occupants.

What can cause cracks to occur?

There are a number of reasons why a structure may form cracks. One of the most common causes of significant wall cracks is poorly compacted foundation ground, or weak, unstable ground conditions, known as subsidence, leading to structural movement. For example, the foundation ground underneath your house may consist of loosely compacted soil or reactive clay, which is affected by varying moisture levels in the ground. Excess water in the ground caused by a change in the water table, or weather events such as heavy and persistent rain, can lead to the ground swelling. This same saturated ground will dry out and shrink when extended warm weather or drought conditions arrive, causing foundations to shift and the building to become unlevel over time.

Superficial cracks can also form as a result of seasonal shifts. It is common for houses to experience subtle movement as a result of building materials reacting to age, weather and temperature changes – this is known as the house ‘settling’. Thermal and moisture changes can also affect the paint, causing it to stretch and break, resulting in cosmetic cracks.

What do I do if I have cracks in my walls? What should I look out for?

The most important thing is not to panic. Take the time to understand your situation to help lead you to the best solution.

You can start by printing out Mainmark’s Wall Crack Guage to help you assess the size of the crack. This handy tool will give you an indication of the severity of the crack. Once you have printed your Mainmark Wall Crack Gauge, you can then ask yourself the following questions:

  • Is the crack 5mm or wider on the Wall Crack Gauge?
  • Is the crack jagged or zig-zagged? And do the cracks originate from windows, doorways or other framing?
  • Is the crack outside? Is it stepped in brickwork or following mortar lines?
  • Are doors and windows misaligned or difficult to open and close?
  • Do the floors also slope or appear to be sinking?

If you answer ‘yes’ to any or all of these questions, the cracks may indicate structural damage or issues with the ground or environment on which your house stands. This means you should consult a professional and obtain advice on how to best repair the damage in the future.

It is possible that the cracks are superficial hairline cracks, caused by natural occurrences such as  seasonal shifting and structural settling. It is still advisable to take action to rectify these cracks, such as taping, re-sealing and re-painting, but there is usually little concern for major short-term damage.

Ultimately, greater knowledge of how cracks can form and what the implications are can prevent added stress and unnecessary costs. Of course, if you’re unsure about how to best preserve your home, a structural engineer or a professional ground engineering company such as Mainmark can inspect the property and provide some further, site specific insight.

For more information and advice about cracks in your home, contact Mainmark on 1800 623 312 in Australia, 0800 873 835 in New Zealand or visit

By Claire Hartley

Claire is a strategic senior marketing and communications professional who joined Mainmark in 2015. She has extensive experience gained in a range of organisations across the APAC region and the UK; from large multinationals and start-ups to industrial B2B, IT and online businesses.

Key considerations when building a stable structure on a difficult site

scaffolding set up on a retaining wall property

Australia and New Zealand are lands of diverse topography, with thousands of communities situated in areas where hills, slopes, embankments and elevations are prevalent. And while that may mean stunning views and natural light for those wishing to live on an elevated site, it raises significant challenges for builders and engineers who must consider the ground terrain and other geotechnical issues.

As a ground engineering specialist, we have seen many examples of challenging building sites, including an elevated property in Parramatta, NSW. A retaining wall between a home and an adjacent public park collapsed shortly after construction. The residence was situated on a very steep slope with a high retaining wall on the property boundary. Mainmark was responsible for backfilling approximately 40m3 behind the new wall with Terefil®, a structural, lightweight, cementitious based fill.

As traditional concrete or fill materials were unfeasible for this project, due to the heavy load they would have placed on the wall, Terefil provided a unique lightweight yet structural solution that allowed the engineers to reduce the wall’s thickness. Terefil’s fully permeable formulation also ensured the wall complied with the engineered specifications for full water drainage.

While sites that feature slopes, cliffs and other scenarios where there is a steep drop in ground levels can make the construction process more complex, they are not impossible for engineers and builders to overcome. The key is to identify the site’s soil and ground bearing conditions to help select the right solution to manage the issue. Here are some common considerations when building on sloping or elevated building sites.

  • Degree of site slope. The steepness of the slope will inform the necessary engineering requirements, site safety considerations, cut and fill work, and ground remediation solutions needed to ensure stable foundations and footings for the structure. Mainmark has successfully worked to remediate many challenging sites, including a duplex property situated on a 20m high sandstone and siltstone clifftop in Auckland, which was experiencing structural damage resulting from unstable ground. In the duplex’s case, Mainmark was required to inject Teretek® engineered resin into ground voids to consolidate the surrounding soil.
  • Ground conditions. The geotechnical properties of soils beneath the surface of a sloped building site can range from hard rock or reactive clay to softer conditions such as sand that may be prone to shifting. These conditions may impact the stability of a sloped site’s foundations. In uncertain ground conditions, a geotechnical report is required to identify the ground’s properties including bearing capacity (or strength) and the presence of any slip planes, which can have a significant impact on the way a building is constructed or remediated. There are ground engineering solutions available that may help to address unstable ground conditions. For example, loose sand that is prone to shifting can be strengthened and consolidated using Permeation Grouting, a solution which agglomerates sandy or loose soils into a cemented mass to support structures and fill voids in the ground. Mainmark used Permeation Grouting to remediate a house in the beachside suburb of Bondi which was affected by subsided footings and a failed retaining wall due to loose sands below the structure.
  • Environmental conditions. Depending on the site’s location, the environmental conditions may need to be addressed. For example, if the sloped site is situated in an area prone to heavy rainfall, a suitable solution to manage overland flows, mitigate saturation of soils and address drainage issues may be required to help stabilise a structure and prevent excess water or runoff from eroding the building’s foundations.

What are the solutions?

Mainmark has a range of products and solutions to help overcome the challenges of building or remediating structures on sloping or elevated sites. In many cases, they can also help avoid the need to use invasive ground remediation processes, such as traditional underpinning and piling, and avert costly repairs down the track should structural damage occur due to poor ground conditions.

Teretek®, Terefil®, and Permeation Grouting are just a few solutions that Mainmark uses to help overcome the complexities of remediating buildings on sloping sites with unfavourable soil conditions.

Teretek is an expanding polyurethane resin mix which is injected through small tubes into the ground beneath the footings. It is ideal for strengthening and re-levelling settled and uneven ground using a process that is likened to keyhole surgery. The application is completed in a fraction of the time compared to conventional re-levelling methods and causes minimal disruption to the site.

Terefil is a lightweight, specialist cementitious fill with a uniformly distributed matrix of air bubbles allowing it to flow into places where other cementitious fills may be unable to reach. Terefil can be supplied as either a permeable or an impermeable cementitous mix, to meet specific project requirements, allowing project engineers to manage ground water flows. It is typically used to backfill load bearing retaining walls, fill voids and sinkholes, and abandon pipes and shafts. Terefil is environmentally inert, cost-effective and uses much less water than traditional options such as cellular lightweight concrete or foam concrete methods.

Permeation Grouting is a commonly used technique for turning granular soils into a solid mass while filling cracks, joints, and other ground defects in non-cohesive conditions. The solution is ideal for resolving ground settlement and subsidence or rectifying other ground problems, such as voids, in locations with soft granular soil or sandy ground conditions.

The secret to building on difficult sites is to design and construct with the appropriate materials for the site conditions, to ensure that a buyer’s ‘house on the hill’ dream is a safe and long-term reality.  Mainmark’s experience and product range provides the designing engineer with targeted solutions to address the demands of the site.

By James O’Grady

James O’Grady is a Sales and Business Development Manager at Mainmark. He is a civil engineer with 25 years’ experience in structural engineering, construction materials and ground treatment.

Inside Mainmark: introducing senior technician, Pip Buunk

Mainmark technicians

Before joining Mainmark earlier this year, Pip Buunk was New Zealand’s only registered female driller, managing drill rigs for geotechnical site investigation, water bore, and geohazard stabilisation projects.

After more than 15 years of working in the drilling industry, and being named the National Association of Women in Construction (NAWIC) Tradeswoman of the Year in 2018, Pip made the move to Mainmark. We recently spoke to Pip about her impressive career and what she loves most about working for Mainmark.

You’ve recently joined Mainmark, but you have worked with the team on different projects in the past. Tell us a little about that.

My career had mostly been in the geotechnical sector of the drilling industry, and about six years ago I started working with Mainmark on a project basis, including undertaking pre and post injection testing for the Northwood Supa Centa and Red Zone trials in Christchurch. I really enjoyed working on these sites, especially the Supa Centa as there were several challenges associated with accessing a drill rig inside the shopping complex. As I had such a positive experience working with the Mainmark crew, when an opportunity to work for Mainmark permanently came about in July this year, I jumped at the chance to join the team.

Can you describe your career journey so far?

I’ve had a pretty amazing career so far. As a ‘fresh out of school’ driller, I have achieved all the goals I set myself, including being elected to the NZ Drillers Federation Council and winning a few awards along the way. I’ve been fortunate to work on some very interesting projects in some pretty amazing locations over the years, however, I have also experienced some significant challenges working as a female in the construction industry. It’s refreshing to join Mainmark as they have a fantastic culture and great people.

As a senior technican at Mainmark, can you tell us about your role and what a typical day looks like for you?

As a senior technician, my days are usually spent working on Teretek resin injection or JOG Computer-Controlled Grouting projects. As a former driller, I have a fascination with resin and grout – I’m like a kid in a candy shop. The products are very different to other grouts I’ve worked with because you can do so much more with them. Since joining Mainmark, I’ve travelled to many different sites in Auckland, the middle of the North Island, Wellington and Christchurch. Currently I’m working on a large civil works project for a water treatment plant where we are undertaking testing and geotechnical drilling investigations.

What have you learnt in your short time working with Mainmark?

I never knew how much you could do with grout!  I’m also learning about how much can be achieved through team collaboration – we work on some difficult and complex projects and managing client expectations can be stressful but as a team we work together to find a solution. This is one of the reasons why Mainmark is such an awesome place to work.

What do you find rewarding about the work you do?

I like that we leave a building or house better than it was when we first arrived on site and the great feedback we receive from happy clients is always a bonus.

Would you like to see more women in the industry?

In short, yes. Diversity brings a totally different dynamic to the industry compared to being in an environment of masculine energy all day.

What is the most memorable experience you’ve had professionally?

Probably winning Tradeswoman of the Year in 2018. It came at a really rough time in my career when I was dealing with some very challenging experiences, so it was nice to have my work recognised even if I wasn’t feeling like a success at the time.

Can you tell us something that not many people know about you?

I’ve been collecting cacti and succulents since I was in high school. I currently have two which are more than 15 years old, named Spike and Jim, along with about 30 others that do their best to survive without water during my trips away. I’m also a power lifter and have been known to put my workmates over my shoulder and squat with them!

By Pip Buunk

Pip Buunk was New Zealand’s only registered female driller, managing drill rigs for geotechnical site investigation, water bore, and geohazard stabilisation projects. She has 15 years experience in the drilling industry, and was named the National Association of Women in Construction (NAWIC) Tradeswoman of the Year in 2018.