When it comes to installing a patio, many homeowners focus on choosing the right pavers or tiles. While these choices are important, the success of your patio depends largely on what lies beneath: the subbase. A well-prepared subbase ensures your patio stays level, drains properly, and resists shifting over time. Let’s dive into the essentials of building a strong patio subbase.

What Is a Patio Subbase?

A patio subbase is the layer of material beneath your patio’s surface. It acts as a supportive foundation, for the weight of your patio

Why Is a Subbase Important?

• Stability and Durability: A solid subbase prevents pavers from shifting or sinking.

• Drainage: Properly installed subbases allow water to drain away, reducing the risk of pooling or erosion.

• Prevention of Cracks: A level subbase reduces stress on pavers, preventing cracks and damage.

Materials for a Patio Subbase

There are 2 main materials that can be used for a patio subbase, each offering different benefits:

• MOT Type 1 aggregate: One of the most popular choices, MOT Type 1 provides excellent drainage and compacts well.

• Concrete: Often used as a sub base for porcelain paving slabs.

• Geotextile Fabric: Placed beneath any subbase material, this fabric prevents soil erosion and keeps the layers separate.

Steps to Build a Patio Subbase (How we do it at Grounds & Greens Ltd)

Geo textile membrane and first layer of MOT Type 1 aggregate

1. Excavate the Area:

Start by digging out the area for your patio. The depth will depend on a few factors such as subsoil material, type of pavers and the climate, but typically, you’ll need to excavate to a depth of 150-200mm

2. Install a Geotextile Fabric:

Laying a geotextile fabric will help prevent weeds and keep the subbase material from mixing with the soil.

3. Add the Subbase Material:

Spread the MOT Type 1 evenly across the excavated area. Aim for a depth of about 100-150 mm, depending on the size and load of the patio.

4. Level and Slope:

Ensure the surface is level but slightly sloped towards an adequate drainage outlet, such as an ACO or gravel drain. A slope of about 1:60 is typically recommended.

5. Compact the Subbase:

Use a plate compactor to press the material down firmly. This step is crucial for creating a stable foundation. Compact in 50 mm, ensuring each layer is firm before adding more material. It is recommended to do 8 passes with the compactor plate per each layer

Compacting with Whacker / Compactor plate

Common Mistakes to Avoid

• Skipping Compaction: Failing to compact the subbase can lead to sinking or shifting over time.

• Using Improper Materials: Avoid materials like pea gravel, sharp sand or soft soils, or recycled products as they don’t provide adequate support.

• Inadequate Depth: A shallow subbase may not support heavy loads or withstand freeze-thaw cycles.

Final Thoughts

Unfortunately this is often an area where corners are cut to save costs as it cannot be seen, however, this is an essential step to ensure a long lasting high quality patio

Building a proper patio subbase is an investment in the longevity and durability of your outdoor space. While it may require extra effort upfront, a well-prepared subbase will save you time and money on repairs down the road. If you’re planning a patio project and want professional guidance, feel free to reach out to Grounds & Greens Ltd.

Ready to get started? Contact us today to discuss your dream patio project!

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