Sub-Base and Capping Layer Installation

Sub-base and capping layers form the structural foundation beneath road pavements and hard standings.
Materials include Type 1 granular sub-base, cement-bound material, and recycled aggregates.
Large volumes of material are delivered by HGV tippers and spread by graders, dozers, or loading shovels.
Compaction by vibrating rollers is required to achieve specification density and bearing capacity.
Dust from dry granular materials can contain respirable silica, requiring suppression and monitoring.
Multiple plant items operating simultaneously on the formation creates high plant-pedestrian collision risk.
Level and thickness control using surveying instruments ensures the layer meets design tolerances.
Haul roads carry heavy traffic during material delivery, requiring maintenance and dust control.
Cement-bound materials are caustic when wet and require COSHH controls for skin and eye protection.
Compaction testing must confirm each layer achieves the required density before the next layer is placed.

Plant interaction	Multiple heavy machines operating together on the formation create constant collision risk for ground workers.
Dust exposure	Dry aggregate and cement-bound materials generate silica and cement dust harmful to lungs and skin.
Structural quality	Under-compacted or incorrectly specified sub-base causes premature pavement failure and costly reconstruction.

Do

Don't

Segregate pedestrian workers from heavy plant operating on the formation
Use banksmen where plant visibility is restricted during spreading and tipping
Apply water suppression to control dust from dry granular materials
Wear RPE when working near dry material spreading or cement-bound mix operations
Test compaction density at the specified frequency before placing the next layer
Maintain haul roads to reduce plant vibration, dust, and vehicle damage
Check material quality certificates against the specification before accepting delivery
Wear chemical-resistant gloves and eye protection when handling cement-bound materials
Brief the team on plant movements, tipping areas, and exclusion zones each morning
Verify layer thickness and level using surveying instruments during placement

DON'T allow ground workers on the formation while rollers are compacting
DON'T accept material deliveries without checking against the approved specification
DON'T spread material without dust suppression in dry and windy conditions
DON'T place the next layer before compaction testing confirms the current layer passes
DON'T walk behind tipping vehicles discharging material onto the formation
DON'T handle wet cement-bound material without gloves and eye protection
DON'T allow haul roads to deteriorate with ruts and standing water
DON'T ignore roller vibration exposure — manage operator time on compaction equipment
DON'T compact in lifts thicker than the specification permits for the material type
DON'T skip level checks — incorrect thickness wastes material and weakens the pavement

See also: Road Construction Safety Awareness | Compaction and Rolling Procedures

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