Paving Base Depth | Sub-base for Driveways and Patios

The layers under paving

Segmental paving, such as concrete blocks, clay pavers and cobbles, is built in layers. From the bottom up: the natural ground, sometimes improved; a compacted sub-base of crushed stone or a similar material that carries the load; a thin, screeded bed of sand that the pavers sit in; the pavers themselves; and sand brushed into the joints. Each layer has a job. The sub-base spreads the load; the bedding sand lets the pavers sit level; the joint sand locks them together.

What one Johannesburg contractor specifies

Sinqobile Construction's published 2026 guide gives this specification: a sub-base of G5 crushed stone 100 to 150 mm thick, a 25 to 30 mm levelling layer of G2 crusher dust, 25 to 30 mm of sharp river sand as bedding, and kiln-dried sand in the joints. It also says heavy vehicles need a thicker base. That is one contractor's specification, not a national standard, but it gives you something concrete to compare quotes against.

Sources: Sinqobile Construction, Paving costs in Johannesburg 2026 (a paving contractor's published guide)

Why depth depends on your site

There is no single right depth for every property. Three things change it. First, the load: a patio carries feet, a driveway carries cars, a shared complex driveway carries refuse trucks. Second, the ground: South Africa's housing site classes separate stable rock from expansive clays, collapsible soils and compressible soils, and each behaves differently under load and moisture. Third, water: wet ground is weaker, so a site that drains badly needs either better drainage or a stronger base, or both.

A contractor who gives you the same depth for every job without looking at your ground is guessing. One who digs a test hole, looks at what is under your old paving and explains their choice is doing it properly.

Sources: GGDA geotechnical investigation report (NHBRC site class designations)

Site classes in plain language

R: rock. Stable, but hard to excavate.
H, H1 to H3: expansive soils, mostly clays, that swell when wet and shrink when dry.
C, C1, C2: compressible and potentially collapsible soils, often silty or sandy, that can settle when wetted under load.
S, S1, S2: compressible soils that settle gradually under load.
P: special cases, including dolomite areas, fill, mining ground and marshy ground.

These classes come from the guidelines used for house foundations. A paving contractor will not test your soil to that standard, but if your property has a geotechnical report, it will say which class applies, and that is useful for the paving design too.

Sources: GGDA geotechnical investigation report (NHBRC site class designations)

Compaction matters as much as depth

A thick sub-base that is not compacted is worse than a thinner one that is. Good practice is to place and compact the sub-base in layers, with a plate compactor or roller, at the right moisture content, rather than tipping it all in at once and running over the top. Ask each contractor how they will compact and how many layers they will use.

Questions to put to every contractor

How deep will you excavate, and why that depth?
What material will the sub-base be, and how thick once compacted?
Will you compact in layers? With what?
What bedding sand and joint sand will you use?
What will you do if the ground is soft or wet when you dig?
Does my driveway need a thicker base for any vehicle that uses it?

Our guide to comparing paving quotes covers the rest of the quote.

Frequently asked questions

How thick should a driveway sub-base be?

One Johannesburg contractor's published guide specifies 100 to 150 mm of G5 crushed stone, thicker for heavy vehicles. Your site may need more or less; ask why.

Can paving be laid on sand only?

Not for a driveway. Sand alone does not carry vehicle loads. Light garden paths are sometimes laid on thinner bases.

What is G5?

A grading of crushed stone material used for road and paving layers in South Africa. Ask your contractor to name the material on the quote.

How deep should a paving base be?