How to Properly Construct a Deep Sub Base for Your Patio

It acts as a foundation for the patio, preventing it from sinking or shifting over time. The recommended depth for the sub base is typically around 150mm or 6 inches from the finished patio level. To ensure accuracy, it’s advisable to use a tape measure to confirm the depth before proceeding further. Once the desired depth is achieved, the next step is to compact the soil using a vibrating plate compactor, commonly referred to as a Wacker Plate. This compactor helps to eliminate any air gaps and consolidate the soil, creating a solid and level surface for the sub base.

Can You Lay Sub-Base on Soil?

When it comes to constructing a patio, one of the most crucial aspects is the proper construction of a deep sub-base. This sub-base, also known as the foundations deepest layer, serves as the solid groundwork upon which your patio will be built. Many people wonder whether it’s possible to lay a sub-base directly on soil, and the answer is yes.

However, it’s important to note that the type of soil you’ve as your sub-base can vary depending on your location. For instance, if you reside in an area with a high clay content in the soil, it can present challenges when constructing a sub-base. Clay soil tends to retain water, which can lead to poor drainage and potential issues with your patios stability. In such cases, additional measures may need to be taken to ensure proper drainage, such as incorporating a layer of gravel or installing drainage pipes.

Regardless of the type of soil you’ve as your sub-base, it’s crucial to properly prepare it before laying any materials. This involves removing any vegetation or debris from the area and compacting the soil to create a firm and level surface. You may also need to consider adding a geotextile fabric to prevent weed growth and improve stability.

Ensuring the proper thickness of a subbase is essential for the durability and stability of any construction project. For areas with foot traffic, a minimum thickness of 75mm is recommended, while domestic driveways should be laid to a thickness of 100mm to 125mm. To achieve optimal compaction, a vibrating drum or a “waker plate” can be used. Finally, maintaining a finished surface that doesn’t deviate by more than +/- 10mm is crucial for a smooth and safe subbase.

How Thick Should Sub-Base Be?

When it comes to constructing a deep sub base for your patio, one important factor to consider is the thickness of the subbase. The subbase should be laid to a minimum thickness of 75mm if it will be subject to foot traffic. This ensures that the subbase is strong enough to support the weight of people walking on it without sinking or collapsing. For areas that will be used for domestic driveways, the subbase should be even thicker, with a recommended thickness ranging from 100mm to 125mm.

To ensure that the subbase is properly compacted and solid, it’s essential to use a vibrating drum or a “wacker plate”. This equipment will help to evenly distribute the weight and pressure across the subbase, compacting it and creating a stable foundation for the patio. Proper compaction is crucial to prevent future settlement and ensure the longevity of your patio.

When constructing the subbase, it’s important to pay attention to the finished surface. The surface of the subbase shouldn’t deviate by more than +/- 10mm. This is because any deviation greater than this can impact the integrity and levelness of the final patio surface. Ensuring a consistent and even surface for the subbase will ultimately contribute to a smooth and stable patio construction.

Proper compaction using a vibrating drum or wacker plate is essential to create a solid foundation.

When it comes to laying a concrete slab, one crucial step is to determine the depth of the sub-base. In general, it’s recommended to excavate the slab area to a depth of approximately 7 inches. This depth allows for a 3-inch layer of gravel base, providing stability and suitable drainage, followed by a 4-inch layer of concrete for the slab itself. This combination ensures a strong and durable foundation for your concrete project.

How Deep Should Concrete Sub-Base Be?

When it comes to constructing a deep sub-base for your patio, one crucial aspect to consider is the depth of the concrete sub-base. Experts recommend excavating the slab area to a depth of approximately 7 inches. This depth allocation allows for the proper installation of a gravel base and a subsequent 4 inches of concrete.

The initial 3-inch layer of gravel serves as a stable foundation for your patio. It helps to distribute the weight and pressure evenly, preventing any potential sinking or shifting over time. This gravel base acts as a support system, enhancing the durability and longevity of your patio.

After establishing the gravel base, the next step involves pouring a 4-inch layer of concrete. This depth is crucial in providing sufficient strength to support the weight load and endure the test of time. It also ensures that the concrete is thick enough to withstand various weather conditions, preventing cracks and other potential damages that may arise.

This level surface isn’t only aesthetically pleasing but also essential in providing a safe and comfortable space for you and your family to enjoy.

This depth is essential for stability, strength, drainage, and maintaining a level surface.

Source: Pouring & Finishing Concrete Slabs – Quikrete


The recommended depth for digging is approximately 150mm or 6 inches from the finished patio level. By following these guidelines, you can establish a solid foundation for your patio, guaranteeing it’s durability and longevity.

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