A slab-on-grade foundation involves pouring a monolithic concrete slab that serves the primary structural element and rests directly on prepared subgrade soil. Each system addresses problems such as settling, heaving, or lateral movement. Below is an overview of various foundation repair systems, highlighting their applications and effectiveness:
- Steel Piers
Steel piers are a popular choice for deep foundation stabilization. They are driven deep into the soil until they reach a stable stratum, offering a long-lasting solution to foundation settling. This system is particularly effective in variable soil conditions where depth to stable soil layers vary significantly. Installation is less invasive and can be completed quicker than traditional concrete piers.
- Helical Piers
Helical piers are similar to steel piers but include plates welded onto the shaft that help with deeper penetration into the soil, using a screw-like action. They are ideal for lighter structures such as decks, residential buildings, and soil conditions requiring precise load-bearing capacity adjustments. Helical piers are also helpful in lifting settled foundations and providing foundational support for new constructions.
- Concrete Piers
Precast concrete piers are used in underpinning to extend the foundation depth to more stable soil layers. This method is cost-effective and suitable for heavier structures. However, the installation process is labour-intensive and can be more disruptive to the property.
- Polyurethane Foam Injection
A more modern approach involves injecting high-density polyurethane foam into the soil beneath the foundation. The foam expands, filling voids and lifting the foundation to its original position. This method is quick, less disruptive, and effective for correcting minor settlements. It is also used for soil stabilization beneath the foundation.
- Segmented Piers
Segmented piers are a cost-effective alternative. They consist of interlocking concrete segments pushed into the ground using hydraulic rams. They are suitable for light to moderate load-bearing applications and are advantageous in tight access areas.
- Slab Jacking
Slab or mud jacking involves pumping cement, sand, and other additives under the slab foundation. The pressure lifts the foundation to its original position. This method effectively corrects uneven concrete floors and is less expensive than complete foundation replacement.
- Wall Anchors
Wall anchors can be installed for lateral movements or bowing in basement walls. These involve embedding anchors in stable soil away from the wall and connecting them with rods to steel plates on the wall interior. This stabilizes the wall and can be tightened over time to straighten the wall progressively.
- Carbon Fiber Straps
Carbon fibre straps provide a non-invasive solution for reinforcing basement walls against inward bowing. They are bonded to the wall using epoxy, creating a solid reinforcement that prevents further movement. This method is less intrusive and maintains the usable space within the basement.
