Information: Installation Guidelines These guidelines are based on SANS 1200MJ, the official South African specification for the installation of paving. Important: Earthworks (base layer preparation) are site-specific and fall within the scope of an engineer’s expertise. Bosun strongly advises that an engineer design any paving’s earthworks. This is imperative for commercial, public and industrial sites intended to carry heavy vehicular traffic.
Terminology: • Sub-grade is the prepared natural earth on which paving will be installed. • Sub-base is the prepared layer beneath the paving and bedding sand. (In South Africa it is usually “natural earth”, unless otherwise specified by an engineer. In other countries it is usually a special imported material, consisting of particle sizes between 40mm and dust.) • Bedding sand is the final layer upon which the paving blocks are installed. • Jointing sand is used for grouting between pavers. • Earthworks or base preparation (beneath the bedding sand.) • The soil conditions and application will determine whether a special sub-base is required. An engineer is required to calculate the need and specification. This will involve excavation and back-filling. • For domestic driveways and paving subjected only to pedestrian traffic, good-quality natural earth might provide sufficient strength for the installation of paving. (However, if you want your paving to last a lifetime, insist on an imported sub-base.) Sandy and clay soil conditions will always require a specially designed sub-base.
Compaction: • Good compaction of the sub-grade and sub-base is critical for your paving installation to last, whether you use an imported sub-base or not. Good compaction means compaction in layers and not merely the compaction of the top soil. In practice, this means taking out soil, compacting, putting some soil back, compacting, etc. • Hand-stampers and small plate compactors are simply not good enough to achieve good compaction. We recommend the use of a mechanical roller.
Bear in mind that: • Excavation is usually required on areas intended for paving. The extent of excavation is determined by the thickness of pavers to be used together with their bedding. • In most instances, excavated material will need to be removed from the site. • There might be natural depressions in the earth of the area to be paved and, depressions, special materials will be required to fill them. On residential driveways, excavated earth is generally usable. Bedding sand should not, in any circumstances, be used for this purpose. • All plant material and roots must be removed from the soil and site. • Carefully consider the roots of trees that might eventually grow under the paving. • Carefully consider underground utilities prior to excavation and digging. • After excavation, “drainage levels” must be checked and rectified.
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