Advantages of a waffle raft slab in comparison to a conventional stiffened raft slab

What are waffle raft slabs, and how are they constructed?

Waffle rafts are a particular form of raft slab where the raft, including ribs, is constructed on a prepared flat ground surface. The regular grid of ribs is formed using void formers.

The construction is completely on-ground rather than in-ground like a conventional raft slab and this has several features:

  • The shrinkage behaviour is improved due to the lower restraint compared with a raft with embedded beams.
  • The structural performance is enhanced, as there is no concern about the down-drag of embedded beams due to clay shrinkage. Conventional raft slabs are susceptible to this.
  • The proportions of the cross-section may be achieved reliably without excess concrete being needed due to over-excavation. Quantity of materials is generally more accurate with a waffle raft.
  • There is a greater propensity for ingress of moisture under the slab.

Adequacy of Drainage

Waffle raft slabs are commonly utilised in the NSW residential market because construction is more controlled and less impacted by wet weather.

Regardless, the benefit of a waffle raft slab is that it has a flat building platform preparation level so rainwater runoff can be drained, providing that there is adequate temporary and permanent site drainage.

Alternatively, conventional raft slab tends to be more affected if an extended period of wet weather were to be experienced following the excavation of all the beam trenches. The trench walls and bases could become soft and will require to be re-excavated and dewatered, which would be troublesome and time-consuming.

Our Experience

Here at Residential Engineering, we have a team of professionals with over 30 years of experience in this industry. We have designed over 250,000 waffle raft slabs in NSW following the AS2870 compliances. Contact us today for more information.

What causes cracks in the walls of a home?

Typical causes of wall cracks include:

  • The house settling
  • Trees in close proximity to the home
  • Reactive soil
  • Water damage
  • Structural/design issues

Although the sight of cracked walls or architraves may be quite alarming, it’s actually very common.

The most common places for wall cracks are above doors and windows – this is because these are the weakest points of the wall. If the cracks appear to only be hairline cracks, they can be easily fixed with filler and repainted.

Settling in houses is especially common with new builds, this is because the timber used in the house frame often contains moisture and it can move slightly as it dries out, these cracks from settling are often very thin and vertical.

The Australian climate also, unfortunately, contributes to cracks in walls, our hot dry summers and lack of rainfall leads to the soil shrinking and moving and this places strain on the home’s foundation.

Whilst trees around the property are a beautiful feature, it is often not realised the damage that root systems can cause to homes. Trees with large, complex root structures can spread too close to the house’s foundations and lead to movement. Roots also change the water levels of the soil which can lead to instability within the soil. Before removing a nearby tree from your property you must also take into account that trees root system, removing a tree too close to the home can also change the water levels and stability of the soil.

When should I be worried about a crack in my walls?

If you notice any discolouration around the crack, you should immediately look to investigate. Discolouration around a crack can be a tell-tale sign of a leak somewhere within the walls, to fix this the source of the leak must be identified and the affected wall will need to be replaced to avoid further damage.

If the cracks are larger than a hairline, you should look to have them inspected. Large cracks (larger than 5mm) can indicate a structural problem. The shape of the crack can also shed light on the cause, a crack that appears in a zig-zag pattern can be an indicator of a structural issue as it is following the mortar line in the bricks.

Be sure to take photos and document the cracks in your wall as you notice them, this will be a good indicator of whether the cracks are getting worse or if they are staying the same.

If the wall crack seems like more than just a cosmetic issue, you should call an expert to investigate as soon as possible. The longer structural damage is left untreated, the harder and more expensive it is to fix.

Before trying to fix cracks or damage in your walls yourself, be sure to contact a structural engineer. Residential Engineering offers structural inspections in New South Wales, if you are worried about the cracks in your walls, call us today.


There are many stages in the home construction process, and our team at Residential Engineering is certified to ensure that each home is being constructed structurally correct at various stages during construction.

The common goal in all parties in home construction is to make sure that the home is built safely and in accordance with Australian Standards and the NCC, ensuring you have a beautiful, completed home with no structural issues now or later down the line.

Residential Engineering has a renowned reputation for consistently high-quality work, and our experience guarantees that the results you receive will have been done by our team of professionals. With numerous site engineers attending inspections daily, all projects we are working on receive inspections at every stage of construction.

The main types of inspections we carry out include:
• Pier inspections
• Slab inspections
• Structural steel inspections
• Prepurchase property inspections

Ensure peace of mind that your home has been inspected every step of the way – contact Residential Engineering today!


As we come to the conclusion of the year, and as the harsh restrictions across the country start to lift, the worst of the COVID-19 pandemic seems to be behind us. However, the economic damage that it has caused is on the forefront, with numerous years of predicted recovery in the country’s future.

Fortunately for those in the residential construction industry, there is an integral part for them to play in the government’s plan for recovery. Their two-point plan involves the extension of the HomeBuilder Grant for a further three months to March 2021 and providing extra funding for low-cost finance from the National Housing Finance and Investment Centre (NHFIC). By securing investment in residential construction, they are supporting future jobs for Australian builders at all levels and investing in prolonged economic growth.

The introduction of the HomeBuilder Grant, combined with the low-interest rates and first home buyer incentives, saw a surge in demand for new detached homes. It is expected that its extension will see at least 12 000 new housing projects and between 3 000 and 5 000 new major renovation projects. According to the HIA, this is expected to “add $6 billion in construction work boosting economic activity and supporting hundreds of thousands of workers directly, up and down the supply.”

COVID-19 has also impacted population spread, influencing where this increase in home building is likely to take place. There has been a shift in population growth from high rise apartments to lower density housing and regional locations, with students and young job seekers not being attracted to the cities for education or employment. With HomeBuilder and the First Home Buyers Scheme in place, and this attraction to detached housing over high rise apartments, October has seen detached building approvals hit a 20 year high, with an increase of 18.6% in the three months to October, and are 23.2% higher than the same time last year.

The Federal Government is also providing an additional $1 billion (taking the total to $3 billion) to the NHFIC to provide more low-cost finance to eligible applicants, including community housing providers so they can provide more affordable housing. They have also contributed an extra 10,000 places to the First Home Loan Deposit Scheme. These changes are expected to generate over $1.5 billion in economic activity.

With the government’s investments already taking form and producing visible economic outcomes, the residential construction industry is bound to be a significant contributor to economic recovery in 2021 and onward.


COVID-19 has had a tremendous impact on Australian businesses, and the workers that the industries employ. While the construction industry persevered throughout the peak of COVID-19, contributing to keeping the economy running, the effects of the virus are now being felt within the industry. Building approvals fell 16.4% in May and are expected to decline further, predicting a 40% downturn by the end of the year. The industry is also experiencing the impacts of travel restrictions, with demand from overseas migrants dropping to near zero.

To counteract the effects of this pandemic, the government has implemented the HomeBuilder Program – a scheme that offers eligible Australians $25 000 to put towards their renovation or new build project. The scheme is there to support the 140 000 direct jobs and another 1 000 000 related jobs in the residential construction sector, while also encouraging Australians to contribute to the industry and further restimulate the sector.

In the latest data from the HIA, the program is offering promising results, with new home sales rising by 77.6% in June from a record low result in May. “The rebound in New Home Sales in June does not fully offset the dismal results of the preceding three months and we are cautious of over-interpreting data from a single month. It is a clear indication that HomeBuilder will help protect jobs in the sector in the second half of 2020 and into 2021,” commented HIA Chief Economist, Tim Reardon. While more data is needed before accurate conclusions can be drawn about the impact of HomeBuilder on employment, the government intervention has sparked optimism that the 40% downturn in construction that was anticipated will be significantly improved and will consequently support industry employment.

The scheme can be accessed by those who are completing renovation works between $150 000 and $750 000, or those building a new home valued up to $750 000. At Residential Engineering, our team has experience with every type of dwelling and can provide you with the information and advice you need to make your project a success. We provide a range of professional services including Structural Engineering, Geotechnical and Energy Services and Surveying. With our team of professionals behind every design, we strive to work with innovation and precision to provide the best for our clients.


As the COVID-19 virus continues to impact the lives of all Australians, Residential Engineering would like to share some of the measures we have put in place to protect the safety and wellbeing of our customers, staff and trade partners.

We will now be offering virtual inspections via video streaming services if requested and where possible. We will also ensure that our staff are using all necessary personal protective equipment and asking appropriate screening questions prior to starting work.

Our virtual inspections are available to builders, developers, project managers, strata and building managers, owner-builders and homeowners.

Our inspections team are looking forward to assisting you both virtually and in-person; whatever suits you best.

For more information please contact our team.


The construction and building industry are one of the few industries that have remained relatively unchanged since modern construction techniques were implemented. These traditional methods have been reliable and as a result, remain unchanged. There is no need to alter the process as we are constructing safe, secure, and beautiful homes. However, this isn’t to say that other forms of construction don’t exist – modular construction is a small but growing part of the construction industry and is proving itself to be an invaluable option to housing issues riddling Australian society.

Housing affordability is a well-advertised issue facing Australians at the moment and can be partly attributed to decades of undersupply in many states and territories. With the population set to reach 50 million by 2066, in order to keep with population growth, the construction industry is required to build between 134 250 and 253 240 new dwellings per year. These figures seem feasible considering an average of 224 950 homes are being built per year (since 2015) however; this is assuming that there is even population distribution. 77% of our population growth is directed towards our fast-growing cities – Sydney, Melbourne and Adelaide in particular, which consequently raises home and rental prices. Combine this with a lack of coordination between infrastructure planning and housing supply, the growing disparity between income and rent prices and restrictions on the supply of available land for housing is resulting in suffering for low socioeconomic families.

Housing affordability has been directly linked to the homelessness crisis in Australia; additionally, public housing is also heavily neglected within Australian infrastructure, and with a lack of a skilled labour force in the housing construction industry the issue at hand becomes incredibly layered and complex with no solution seemingly in sight.

Modular construction can provide affordable housing options for low-income families, with savings driven by mass production, reduced construction times and lower labour costs. While traditional housing methods have provided a solid foundation for the construction of our remarkable cities, alternative housing options need to be available to mend the gaps that unaffordable and poorly planned housing developments have left. Modular construction only accounts for 3% of Australians annual construction, but there is certainly an obvious place for it in our industry’s future.


The rapidly growing population has been identified as one of the more immediate issues that most major Australian cities are set to face, with the population projected to reach 50 million by 2066. As current infrastructure construction is struggling to keep up with this growth, it is apparent that current methods of city planning need to change.

As reported by Infrastructure Australia, the Australian Government when developing cities have a tendency to develop outwards rather than consolidate, which leaves these communities poorly designed and often lacking in necessary communal services. These suburban communities are also removed from the majority of work found in the cities, and there is a growing demand to live in the inner cities to reap the social and economic benefits that cities have to offer. With this in mind, we are now seeing the dissatisfaction with ‘suburban’ and the need to turn to ‘urban’. Community dissatisfaction is far from the only consequence of this poor planning – the report finds that urban sprawl will place further pressure on road congestion and will cost an additional $20 billion by 2031 ($18.9 billion to $38.7 billion).

This trend is evident across the majority of Australian cities with Sydney, Melbourne, Brisbane and Perth failing to keep up with population demand and infrastructure growth whilst absorbing three-quarters of Australia’s growing population. As previously mentioned, there needs to be a shift from ‘suburban’ to ‘urban’ by further investing in high rise and unit development to consolidate and centralise cities. This will help satisfy the social and economic needs of the Australian people whilst providing a viable, sustainable and affordable solution to future housing issues. Fortunately, we are starting to see these changes as unit development is becoming increasingly popular.

We at Residential Engineering have been involved in numerous developments of this kind, providing a range of professional services including Structural Engineering, Geotechnical and Energy Services and Surveying. With our team of professionals behind every design, we strive to work with innovation and precision to provide the best for our clients.


From the homeowner to the builder, technology is influencing the way we create homes, the way we function within our homes and the environmental ramifications that our homes produce.

In a fast-paced world like ours, we place extreme value on two things – technology and efficiency. We rely on technology to assist in almost every aspect of our lives, and we rely on that technology to be functional and efficient so we can work at the high speed that is now demanded of us.

But when technology meets efficiency, in most cases there is an unintentional by-product – sustainability. Sustainability is currently just as valued as efficiency and is a highly sought-after feature and marketable consumer feature. Technologies designed to improve efficiency, aim to cut corners, reduce human efforts and regulate energy use – all features which have ramifications on technology’s sustainability and environmental impact.

Take for example the ‘Smart Home’ – defined as a house containing a communication network that connects different appliances and allows them to be remotely controlled, monitored and accessed. Despite dwelling approvals consistently falling in previous months, the demand for smart homes has never been higher. The integration of fuzzy interference systems with key pre-fabricated sustainability features such as the 53kW PV solar panels provides homeowners with the opportunity to make smarter choices about energy consumption with greater ease and promotes the automation of reduced energy consumption through AI learning technologies.

These are technologies that are now being integrated within the design stages of homes and are marketed as being the most sustainable home available. However, this is the final stage of efficiency and sustainability. We are seeing this melding of technology and efficiency within the construction industry, with exceptional environmental ramifications. With energy demand in buildings predicted to rise by almost 50% between 2010 and 2050, and the Australian construction sector generating between 20 to 30% of all waste entering landfills, environmental sustainability has never been a more vital issue to address.

Falling project productivity, the rising cost of raw material and equipment and keeping up with regulatory changes are productivity and environmental issues facing the construction industry. Like with smart homes, technologies designed to improve the efficiency of their work also have sustainability implications. Modular construction has been commended for its energy efficiency and its minimisation of waste in comparison to traditional construction. As these prefabricated parts are factory mass-produced, modular construction is a more accurate form of construction that reduces overall construction time and minimises raw material cost and project productivity.

Biomimicry is also lessening our need for raw materials and further reducing the environmental impacts of raw material mining. This, complimentary with the use of nanotechnologies, is allowing engineers to experiment with smart materials to be mixed into concrete to monitor building energy performance and create advanced paints that have the ability to clean themselves, improve insulation properties of buildings, and absorb air pollutants. These technologies are improving the efficiency of the construction industry while supporting sustainable practices and there is only room for more improvement.

There is huge potential for future pursuits in technology, efficiency and sustainability and we are only now seeing the start of these developments. From the homeowner to the builder, sustainability is being observed and achieved in all levels of home construction, and it is evident that this is something that can be interwoven into all aspects of home creation and design.