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.