chapter  15
9 Pages

External works and other surfaces

An assessment of the subgrade should be carried out to determine the overall construction depths particularly where heavier usage is anticipated. As a guide, Table 30 gives an indication of the likely required overall construction thicknesses for different soils

HGV parks

ISOmmmin thickness Type 1 granular material subbase 150mm thick DBM roadbase 40mm nominal size aggregate 60mm thick DBM basecourse 20mm nominal size aggregate 45mm thick HRA wearing course; mix designation 55/14

Vehicles carrying up to 5 tonnes payload

ISOmmmin thickness Type 1 granular material sub-base

100mm thick DBM roadbase 28mm nominal size aggregate

60mm thick DBM basecourse 20mm nominal size aggregate

30mm thick close graded macadam wearing course; 10mm nominal size aggregate

Private drives

ISOmmmin thickness clean hardcore

60mm thick DBM basecourse 20mm nominal size aggregate

30mm thick close graded macadam wearing course 10mm nominal size aggregate

Public car parks, office

carparks 200mm min thickness clean hardcore

60mm thick DBM basecourse 20mm nominal size aggregate

30mm thick close graded macadam wearing course 10mm nominal size aggregate

Table 29 Typical flexible carpark construction

For the circulatory areas of car parks where use by HGVs is likely or a regular feature, channelisation should be considered and if necessary the access and circulatory areas designed as a flexible road pavement/carriageway.