What is a sub-base and how does it differ from an embankment?

In patio and path construction, the sub-base is the lowest layer of the pavement construction, between formation level and the tile covering. It must be level, structurally stable and frost resistant. It receives loads from the covering and spreads them over a sufficient area for the underlying ground to take them.

In engineering terminology, the embankment is not a layer of the pavement but the built-up earthwork below formation level. Beneath it lies natural, undisturbed ground. In everyday garden and paving work, however, sub-base or base is often used loosely for the entire construction below a tile covering. WARCO uses sub-base in this broader sense.

WARCO distinguishes three groups of sub-base.

Unbound sub-bases consist of sand, gravel, stone chippings or crushed stone. They are laid loose and then compacted. Compaction increases their ability to carry loads without binding the aggregate.

Grid-based sub-bases use gravel grids, also known as grass grids or plastic cellular grids. Their cells are filled with stone chippings. Metal grating of the kind found on some balconies is another variant.

Bound sub-bases form a firm layer whose components act together as a single structural unit. They include hydraulically bound layers such as concrete, bitumen-bound layers such as asphalt, existing surfaces such as concrete block paving, tiles, natural stone slabs, screed or parquet flooring, and waterproofing layers such as a roofing membrane. In highway specifications, only concrete and asphalt in this list are classified as sub-bases. Existing surfaces and waterproofing layers are not.

For WARCO, all three groups count as sub-bases because each of them carries the rubber tiles.