The general principle
A block pavement is not load-bearing on its own. Durability depends above all on:
- the bearing capacity of the subgrade,
- drainage,
- keeping water out of the formation,
- the thickness and compaction of the sub-base,
- lateral restraint from kerbs,
- block thickness, laying pattern and joint filling.
Load categories
| Category | Example | Type of loading |
|---|---|---|
| K1 – Pedestrian | garden, footpath, patio | static, minimal |
| K2 – Car | driveway, garage access | low axle load |
| K3 – Car park | residential or commercial car park | repeated loading |
| K4 – Lorries | industrial yard, warehouse | high axle load |
| K5 – Industrial | forklift, HGV, loading area | extreme demands |
Applicable reference: the Spanish PG-3 specifications and technical recommendations for pavements define the heavy traffic categories and the requirements for granular layers (always check the current version).
Layer build-ups by load category
K1 – Pedestrian surfaces (garden, footpath, patio)
- Blocks: 4–6 cm
- Bedding layer: 3–5 cm of 2/5 or 4/8 grit
- Sub-base: 10–20 cm compacted crushed stone (0/32 or 0/45)
- Note: On clayey or expansive soils use a thicker sub-base. Here the critical factor is, above all, drainage.
K2 – Driveway, garage access
- Blocks: 6–8 cm
- Bedding: 3–5 cm
- Sub-base: 20–30 cm compacted crushed stone
- Note: Edge restraint is mandatory. Typical faults: too thin a base → settlement; a sand base → blocks creeping apart.
K3 – Car park
- Blocks: 8 cm
- Bedding: 3–5 cm
- Sub-base: 25–40 cm
- Note: Circulation lanes need a reinforced build-up. Designing the kerbs and drainage gullies is mandatory.
K4–K5 – Industrial / heavy traffic
- Blocks: 10–12 cm industrial pavers
- Bedding: 3–4 cm (no more!)
- Sub-base: 40–60 cm, possibly cement-treated base (soil-cement / lean concrete) or a concrete base
- Note: Requires engineering design. A cement-treated base or an asphalt/concrete base may be recommended.
Permeable construction
- Blocks: 8–12 cm
- Bedding: special open-graded aggregate (not sand!)
- Sub-base: open-graded crushed stone or a permeable hydraulically bound layer
- Note: Joints and drainage are critical. Only a compatible jointing material may be used.
Sub-base materials
Typical materials (aggregates to UNE-EN 13242):
- 0/32, 0/45, 0/56 crushed stone – the most common sub-base material
- Stabilised granular base – for higher bearing capacities
- Sandy gravel – only for light duty, with a suitable grading
- Cement-treated base (soil-cement / lean concrete) – for heavy loads and industrial applications
- Open-graded crushed stone – for permeable construction
Placing and compaction
- Spreading in layers (max. 15–25 cm compacted layer thickness)
- Keeping to the optimum moisture content
- Compaction with a vibrating roller or a heavy plate compactor
- Level checking with a laser or string line
- Measuring the Ev2 modulus with a plate load test (per the Spanish PG-3 specifications and technical recommendations for pavements; check the current requirement)
Critical mistakes: Placing one over-thick layer (e.g. 40 cm at once) → it will not compact properly. Material contaminated with clay fines or poorly graded → settlement and creep. A sub-base laid on a waterlogged or softened formation → softening and damage.
Summary table
| Use | Blocks (cm) | Bedding (cm) | Sub-base (cm) | Note |
|---|---|---|---|---|
| Pedestrian | 4–6 | 3–5 | 10–20 | Thicker on clay soils |
| Car | 6–8 | 3–5 | 20–30 | Edge restraint mandatory |
| Car park | 8 | 3–5 | 25–40 | Reinforced lanes |
| Industrial/heavy | 10–12 | 3–4 | 40–60 + CTB | Design required |
| Permeable | 8–12 | Special | Open/hydraulic | Joints critical |
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