Precast Concrete in Nairobi: Kerbs, Channels, Slabs and Culverts

Precast is consistent; installation is where it varies

Factory-made units are dimensionally accurate and strength-tested, which is their advantage over casting on site. What varies enormously in Kenya is how they are bedded, and a precast kerb laid badly performs worse than a poorly cast one laid well.

What we supply and lay

Road kerbs for driveway and parking edges. Drainage channels for carrying surface water to a gully. Paving slabs for footpaths and patios. Culverts where a drive crosses a ditch. Copings for boundary walls. Fence posts for perimeters.

Bedding and haunching

Every one of these needs bedding on concrete and, for anything upstanding, haunching behind. A kerb pushed into sand looks identical on handover day and moves in the first rainy season.

Installation frequently costs as much as the unit itself, sometimes more. Any quotation that prices the products and treats laying as incidental is understating the job substantially, and that is the most common way precast work is quoted here.

Culverts

Where a driveway crosses a ditch or a drainage line, a culvert has to be sized for the flow, bedded on a proper base and headwalled at both ends.

Undersized culverts are extremely common on Nairobi plots and they cause the flooding they were meant to prevent. We size for the catchment rather than for the pipe that happens to be available.

Handling

Precast is heavy and brittle in bending. Units dropped or levered into place develop hairline cracks that open later. We handle with the right equipment and we reject damaged units on delivery rather than laying them and hoping.