Construction material quality checks every owner should know

Good workmanship can't compensate for poor materials. These checks won't replace laboratory testing, but they will help you spot obvious problems before they're built into your walls and slabs.

Cement

• Check bags carry the manufacturer's details, the cement class and a KEBS standardisation mark.
• Reject bags with hard lumps — a sign the cement has absorbed moisture.
• Store off the ground, under cover, and use older stock first.

Reinforcement steel

• Confirm bar diameters match the structural drawings — measure them.
• Look for manufacturer markings and avoid heavily rusted or pitted bars. Light surface rust is normal; flaking rust is not.
• Count bars and check delivery notes against quantities ordered.

Sand

• Rub a handful between your palms: if it leaves a lot of fine silt or clay on your hands, it may be too dirty for good concrete or plaster.
• A simple jar test — sand, water, shake and settle — shows how much silt is present.
• Avoid sand with visible organic matter, roots or rubbish.

Ballast (aggregate)

• Should be hard, clean and of the size specified for the work.
• Avoid ballast mixed with soil or that crumbles easily.

Blocks and stones

• Check dimensions are consistent and edges are sound.
• Machine-cut stone and concrete blocks should not crumble when knocked together.
• Count deliveries — and count again before payment.

Concrete on site

• Mix ratios should match the specification, measured with consistent gauge boxes — not shovels.
• Watch for excess water; it makes concrete easier to place but weaker.
• For structural elements, cube samples can be taken and tested at an accredited laboratory, typically at 7 and 28 days.
• Cure slabs and columns by keeping them wet for several days.

Material checks are a routine part of our site supervision visits.

This article is general guidance for property owners in Kenya and is not a substitute for professional advice on your specific project. Regulations, requirements and prices change — confirm current details with the relevant authority or professional.