Granular Type 3 Sub-base for Permeable Flooring

← Back to What sub-base is needed for permeable flooring?

Granular Type 3 Sub-base: What You Need to Know for Permeable Flooring

If you’re considering permeable flooring for your driveway, patio, or pathway, choosing the right sub-base is essential. Granular Type 3 material is often recommended, providing reliable drainage and structural strength beneath permeable surfaces.

What Is a Granular Type 3 Sub-base?

A Granular Type 3 sub-base is a free-draining aggregate layer made with well-graded, angular stone. Unlike traditional sub-bases, Type 3 contains little to no fines (small particles), allowing water to pass through easily and preventing puddling under permeable surface layers. It acts as a stable yet permeable foundation for resin-bound or pebble floors, ensuring longevity and resistance to shifting.

How to Choose and Install a Type 3 Sub-base

When preparing for a permeable floor installation, select a certified Type 3 aggregate, typically composed of crushed stone with particle sizes ranging from 5mm to 40mm. To lay the sub-base:

Excavate to the required depth, ensuring any organic material is removed.
Spread the Type 3 aggregate in layers, compacting thoroughly after each layer.
Aim for a final compacted thickness suitable for your expected load—generally 100–150mm for pedestrian areas, or more for driveways.

Once installed, your sub-base is ready to support a permeable system such as the Flowstone – Complete Permeable Floor Kit.

When Is a Granular Type 3 Sub-base Essential?

A Type 3 aggregate sub-base is particularly important where effective drainage and surface durability are priorities. This is crucial in rain-prone areas or where planning regulations mandate sustainable drainage solutions for new surfaces.

Related guides

What Sub Base Is Needed For Permeable Flooring

Using a Granular Type 3 sub-base is the foundation for any high-performance permeable flooring. For more details on installation and compatible systems, see our main guide on what sub-base is needed for permeable flooring.