It is common to lay a concrete slab for driveways, patios, and other outdoor areas. When it comes to laying a concrete slab directly on the soil, it’s not as easy as saying “yes” or ‘no”. It’s important to prepare the surface properly to avoid any issues.
Why Soil Alone Is Not Enough
Due to weather conditions, moisture, and settling, soil is uneven and unstable. Pouring concrete onto untreated soil may result in:
- Cracking: As the soil expands or contracts, the slab of concrete will also move, causing cracks in its structure.
- Erosion: Water can seep through the slab and into the soil below, causing erosion. This will eventually cause the slab to sink or tilt.
- Unstable Foundation: Concrete can cause uneven settlement if the soil beneath is not compacted and treated properly. This could lead to an unstable foundation which may not be able to support heavy loads.
Steps to Properly Prepare Soil for a Concrete Slab
It’s important to follow certain steps before pouring concrete for it to be stable and long-lasting. They include:
- Excavate the Area: Remove any vegetation, grass, or soil on top of the area you intend to lay your slab. This will stop organic material from decaying underneath the concrete slab, which could cause it to sink.
- Compact the Soil: Use a mechanical compaction machine to compact the soil. Compacted soil creates a solid base for the slab and reduces the chance of it shifting or settling.
- Install a Gravel Base or Sand Base: Spread a layer of gravel, or sand about 4 to 6 inches thick over compacted soil. This layer prevents water from collecting under the slab and helps to drain it.
- Add a Vapor Barrier: To prevent moisture from infiltrating the base, place a plastic vapor barrier on top of gravel or sand before pouring concrete. This prevents water from rising into the slab which could cause cracks and other problems over time.
Although you can technically lay a slab of concrete directly on the soil, this is not recommended for a stable and durable foundation. The strength and longevity of your slab will be enhanced by a proper preparation that includes soil compaction, adding gravel or sand, and compacting the soil. Following these steps will ensure a durable, long-lasting slab that can withstand the elements and heavy usage.
This post was written by a professional at Apexx Enterprise LLC. Adam Ortega founded the company Apexx Enterprise LLC, in 2016 at only 20 years old. Mr. Ortega has become a licensed general concrete contractors Marana AZ like his father and grandfather before him. Apexx Enterprise LLC is licensed, bonded, and insured and it is available for review at the Better Business Bureau. Apexx Enterprise LLC has won many achievements within the Home Advisor platform and we have multiple reviews as well. Their Mission Statement – “Our crew at Apexx Enterprise will perform the highest quality construction services for our customers. We aim to achieve our mission through total service satisfaction and by delivering our services while maintaining the highest levels of professionalism, integrity, and honesty.”
