Author: Matthew Cornell

Older slab-on-ground houses can experience seasonal movement due to soil reactivity and the absence of modern footing designs. Before the adoption/introduction of AS2870, foundation designs often relied on minimal soil preparation and basic reinforcement.

While these methods served their purpose at the time, they often fall short of withstanding the effects of ground movement that modern wall linings (ie plasterboard) need today.

If you’re dealing with seasonal movement causing cracks, uneven floors, or other structural issues, here are three practical tips to help you manage the problem.

1. Improve Drainage Around Your Property

One of the most effective ways to address slab movement is by managing the moisture content of the soil around your home. Reactive soils expand when wet and shrink when dry, causing stress on your slab. To mitigate this:

– Ensure your property has effective site drainage, including properly graded surfaces that direct water away from the house.

– Install or repair gutters and downpipes to prevent water from pooling near the foundation.

These improvements reduce seasonal soil moisture fluctuations, which are a primary cause of slab movement.

2. Consider Underpinning or Slab Jacking

If your slab has already experienced significant movement and is no longer moving, it may have subsided and could benefit from additional structural support. Underpinning and slab jacking are two techniques commonly used for reversal of one-way downward movement:

Underpinning: This involves supporting the foundation in a deeper, more stable soil layer. It’s a permanent solution that addresses erosion and/or soil consolidation issues.

Slab Jacking: This process raises and levels the slab by injecting grout or expanding foam beneath it, filling voids and restoring structural integrity.

Both methods require professional assessment and execution, so consult a structural engineer to determine the best option for your home (Beware: Don’t ask a slab jacking or underpinning “salesperson” at this stage!!!)

3. Monitor and Maintain Consistent Conditions

Preventing future movement involves proactive monitoring and maintenance. Small steps can make a significant difference over time:

– Monitor new or existing cracks for changes in size and direction, as these can indicate ongoing movement.

– Maintain a consistent moisture level around your foundation by avoiding overwatering gardens near the house and ensuring tree roots are kept in check.

By addressing potential issues early, you can reduce the risk of costly repairs and extend the life of your foundation.

Professional Advice Matters

Every house is unique, and older homes often come with their own set of challenges. If you’re experiencing recurring movement in your slab-on-ground house, it’s essential to seek professional guidance. A structural engineer can assess your property, identify the root cause of the movement, and provide tailored solutions to protect your home.

Addressing movement in older homes can feel overwhelming, but with the right approach, you can restore stability and peace of mind.

What To Do If You Don’t Agree with Your Engineer’s Report or Drawings

Engaging an engineer to provide a professional service is an important step in bringing your project to life. However, disagreements can occasionally arise, and it’s vital to know your options if you’re not satisfied with the engineering report or drawings you’ve received. Here’s some practical advice to help you navigate the situation constructively:

Start with Open Communication

At Cornell Engineers, we value open and honest communication. If you have concerns about the design or report, give us a call. We welcome the opportunity to understand your concerns, clarify any issues, and work towards a solution that works for you.

Escalate the Issue to the RPEQ

If the matter remains unresolved, you can escalate it to the RPEQ (Registered Professional Engineer of Queensland) responsible for the work. Every RPEQ has a responsibility to uphold professional standards and can review the concerns raised.

Review the Contract

Carefully examine the scope of work and deliverables outlined in the contract. This will help ensure that the engineer’s work aligns with what was agreed upon.

Request a Site or Office Meeting

Sometimes a face-to-face discussion can help clear up misunderstandings or address concerns more effectively. A site or office meeting with your engineer can provide clarity and lead to a collaborative solution.

Review the Terms and Conditions

Before taking further action, carefully review the terms and conditions of your agreement with the engineering firm. This can provide insight into what services were promised and help determine the next steps.

Provide Feedback

Sharing constructive feedback with your engineer is helpful in resolving the issue and improving their service. It could be as simple as pointing out specific areas of concern in the report or drawings.

Lodge a Complaint

If open communication and meetings don’t resolve the issue, most engineering firms have a formal complaints process. Use this as an opportunity to escalate your concerns within the organisation.

Be Mindful of Non-Registered Engineers

If the work was completed by a non-registered engineer in Queensland and was not supervised by an RPEQ, you are not legally required to pay for the work. In such cases, report the matter to the Board of Professional Engineers Queensland (BPEQ).

Leave Reviews to Help Others

If your issue is resolved (or not), consider leaving a review for the engineering firm. This helps others understand what to expect and holds businesses accountable for the services they provide.

At Cornell Engineers, we believe in resolving issues through constructive conversations. We’re here to listen, discuss, and help you get the outcome you’re looking for. If you have any concerns about our work, don’t hesitate to call us. Let’s work together to ensure your project moves forward with confidence.

If you’re facing challenges with an engineering report or design, call us today—we’re here to help!

When designing site drainage, do you even need an ag pipe?

Big hint: Water flows through gravel without an ag pipe.

Here’s the order of the universe:

Gravel – Highly porous with large particle sizes that allow water and air to pass through easily.

Coarse Sand – Very porous, with relatively large particles and low water retention.

Fine Sand – Moderately porous, smaller particles than coarse sand but still allows significant drainage.

Loamy Sand – A mix of sand and some silt and clay, moderately porous but retains more water than pure sand.

Loam – A balanced mix of sand, silt, and clay, providing moderate porosity and good water retention.

Silt – Less porous than loam, with smaller particles that retain water well but drain more slowly.

Sandy Clay Loam – Less porous, with a higher clay content that reduces permeability.

Clay Loam – Low porosity due to a high clay content, retaining water more effectively.

Clay – Least porous, with very small particles that make drainage extremely slow and retain water tightly.

So before you shell out the money for an ag pipe, take a minute to determine what you are trying to achieve.

We’ve said it before and we’ll say it again: Ag pipes don’t magically make water flow uphill!

• Grade the base of your drainage trench in the direction you want water to flow.
• Use a geofabric (or not – it’s up to you) to minimise silt loading.
• Use 10mm or 20mm gravel in your drainage trench to allow water to flow down the hill/grade.
• Discharge water without causing a nuisance to your neighbours.

Water that sits in gravel-filled trenches also soaks into the ground. It doesn’t ALL drain down the hill. Think about where you position your drainage trench and the effect of water soaking into your ground.

Best of luck!

Water Ingress or Site Drainage Problems? Take Action Now!

If you’re dealing with water ingress or site drainage issues, you probably already know the problem isn’t going to fix itself. Like the boy who stuck his finger in the dike, the key is taking action.

What you don’t need is another quote, another opinion, or another lengthy report gathering dust. What you do need is to act decisively.

Sometimes, the first solution doesn’t fully solve the problem—that’s just part of the process. But every step you take brings you closer to a lasting fix. Waiting only makes the issue worse.

Let’s stop the water in its tracks.

If you’re ready to take the next step, contact us today.

Builders stop reading plans when engineers issue poor-quality drawings. Then, when things go wrong, builders have no explanation for the failure.

How about this: make your engineers provide what they were engaged to do.

READ THE PLANS.

If engineers issue poor-quality plans (or reports) send them back to be fixed. Force your engineer to provide what they were engaged to do.

Builders: stop carrying the risk of poor-quality plans.

1. Read the plans.

2. Ask lots of questions.

3. Get errors and missing information fixed.

Put the risk back on your professional engineer. You paid an engineer so you have someone to blame. Get your money’s worth!

(First published on Cornell Engineer’s Facebook Page)