Ground preparation for paving – base layers, aggregate and bedding

Set the finished level and water route

Compare the proposed surface with buildings, steps, paths and retained edges. Look for places where water collects or would run towards a building. A surface that looks level still needs a planned route for rainwater.

Will the paving carry pedestrians or vehicles? Check for soft ground and persistent wetness before choosing a build-up. Ground conditions and loading affect the structure; paving over an unresolved weak patch does not make it sound.

Work down through the whole build-up

From the finished paving level, subtract the thickness of the pavers or slabs, the finished bedding thickness and the other structural layers in the chosen design. This gives the level of the structure's underside.

Hypothetical level calculation: 6 cm paver + 3 cm finished bedding + 15 cm finished base = 24 cm. In this example, the structure's underside is 24 cm below the finished surface. These are arithmetic assumptions, not a recommended paving specification.

Compare that level with the existing ground. If the ground is already at the intended finished level, the example needs 24 cm of space below it. Raising the surface or retaining suitable existing construction changes how much must be removed. The total build-up is not automatically the excavation depth in every situation.

Match materials to their jobs

The structural base or sub-base distributes loads and establishes levels. Select its aggregate, thickness and construction method for the ground and intended use.

Bedding provides an even laying surface directly beneath the paving. Its material and installation method belong to the chosen paving system. Do not make it thicker to hide major errors in the structural base.

Names vary between suppliers and between Britain and Australia. Check grading and intended use, not just a label such as crushed rock or crusher dust. Fine quarry material is not automatically suitable as a general structural base or as bedding for every paving product.

Build in stages and order in the right units

Place and compact structural layers in lifts according to the selected specification. Check levels before covering each stage. Bedding follows its own installation instructions; it need not be treated like the base.

Quantity example: 24 m² × 0.15 m = 3.6 m³ of finished base. The thickness is an example assumption.

Ask the supplier how much of the selected product is needed to produce that finished layer. Clarify whether its figures describe loose delivered material or the finished compacted state. Multiplying compacted volume by an unrelated loose bulk density does not establish the final order in tonnes.

Check before laying the paving

Finished levels, the water route and edge restraint should be resolved. Check layer levels and thicknesses and deal with any remaining soft areas before laying. Bedding must be able to do its own job rather than disguise an inadequate base.

These checks help you decide whether to move to the laying stage. They are not a structural certification.