How to lay kerbstones

Only when the pavement is firmly supported and constrained by proper kerbing or edging on the periphery can it be successful. It’s also vital to keep vehicular traffic from going beyond the built-up area. Kerbing or edging is also required to keep the laying course at the bottom of the pavement and to effectively handle horizontal loads that could cause paving segments to shift within the overall pavement. Because kerbs must withstand vehicular impacts, they must be of high quality and long lasting. They must also be installed correctly in order to be effective and suit the purpose and intent. Some NS Certified kerbstones are available in Nepal which are durable and reliable like the Asian kerbstones.

Installation of concrete kerbs, edging and channel units has five main stages:

  1. Preparation of support layersThe unit foundation must be supported either by an extension to the underlying pavement sub-layers or directly on a sufficient subgrade for thin pavements (e.g. edgings on pedestrian footways). The kerb foundation will be installed on which pavement layer depends on the depth of the unit and the pavement structure.
  2. Construction of unit foundationA solid concrete foundation (kerb race) is required to support the unit and must be adequate for pedestrian or vehicular traffic. It must be able to evenly distribute and transmit the applied vehicle wheel loads to the underlying support layer without overstressing it. Overrun shear forces must also be able to be resisted by the foundation.
  3. Laying to line and levelKerbs and edgings, in particular, are designed to serve as visual markers, highlighting the edge of a pavement or signaling a change in level. As a result, they must be put to the precise line and level, as any disparity would stand out and detract from the finished pavement’s beauty. When utilized to transport water, channels must be precisely laid to the exact line and level. Any change in line and level can disrupt the smooth water flow, causing localized ponding and the possible deposition of waterborne sediment.  
  4. Bedding of unitsTo provide even support and prevent vehicular overrun from damaging the unit by creating bending strains, kerbs, edgings, and channels require bedding. The units can be directly bedded on a freshly mixed concrete kerb race, on mortar on a hardened kerb race, or bonded directly to the pavement surface with a modified stronger mortar or suitable resin compound.
  5. Haunching of unitsUnless the neighboring paving can provide appropriate support, such as flush installed channel units in block paving, units should be haunched with backing concrete to support them and prevent horizontal displacement


Concrete kerbs are typically laid with unfilled, close joints with a minimum joint width of 2 mm; butt-jointed kerbs are not permitted. Mortar joints are optional, however they can be employed for aesthetic purposes. The mortar should be newly made, with a cement-to-sand ratio of 1:4. (by volume). When using mortar joints, make sure they are properly filled and compressed. Joints should be 5-7 mm wide.

Suitable joints should extend across the line of the units at the joint and continue through the kerb race and haunching concrete where units are constructed over or adjacent to a jointed concrete pavement. Movement joints should be given when mortar joints are employed. These movement joints should be 10 mm thick and easily compressible, reach through the kerb race and haunching concrete, and be spaced 15 m apart. Mortar should be utilized right away, and any material that has started to set or has been mixed for more than two hours should be destroyed.

Setting-out and Alignment

A string line between pegs or steel pins is used to set out units to line up and level them. After that, examine the line and level of the laid units, and make any necessary modifications. Because the string line will consist of a sequence of straight lines, allowances should be made for curves. The units are examined for final alignments to verify that they follow a smooth horizontal and vertical curvature. Radius kerbs should be used for radii of 15m or less when utilizing kerbs per EN 1340: 2003.

Units should be laid to within 10 mm of their design alignment, with a maximum deviation of 3 mm between neighboring units. The water check should generally be 25 mm above the road surface while laying kerbs. Unless otherwise specified, kerbs at vehicle crossing points should be 25 mm above the final road surface.

Dropped kerbs should be installed 6 mm above the final road surface on the lower side of the road and level with the surface on the higher side to improve drainage at pedestrian crossing sites. The upstand should be between 0 and 6 mm to make wheelchair use easier. To accomplish this, the dropper units’ joints may need to be adjusted. At this stage, a drainage outlet may be required for the removal of surface water in this application.

Cutting Units

The long kerbs should not be cut to less than 300 mm in length, with smaller units not being cut to less than 1/3 of their original length (and a minimum of 50 mm)