What to check before you buy cabro
Most paving that fails in Kenya was not a bad product. It was the right product on the wrong base, or the wrong thickness, or blocks that were not what they were sold as. Eight things to check, and how to check each in five minutes.
Under-specified thickness
50mm on a driveway that a lorry will one day use. Match thickness to the heaviest vehicle that will ever come in, not the everyday one.
Check it: Ask: what is the heaviest vehicle that will ever drive on this? Then read the thickness guide.
Skipping black cotton removal
The single most common cause of sunk paving in Syokimau, Kitengela, Athi River and parts of Ruiru. It must come out.
Check it: Ask the contractor to dig a test pit in front of you. Black cotton is dark, sticky when wet, and cracks into blocks when dry.
No edge restraint
Without kerbs or a concrete haunch, the outer rows creep, joints open, and the whole area loosens.
Check it: Look at the quote for kerbs or a concrete haunch, priced per metre. If it is not there, it is not being done.
Hand-moulded instead of machine-pressed
Hand-moulded blocks are weaker, vary in size and chip easily. Check for sharp, consistent edges and a dense face.
Check it: Pick up two blocks and put them face to face: they should match exactly. Run a coin along an edge: it should not crumble.
Blocks sold before 28 days
Concrete needs 28 days to reach strength. Freshly pressed blocks chip during laying and compaction. Ask the pressing date.
Check it: Ask the pressing date of the batch. Reputable yards stack by date and will tell you.
No falls for drainage
Level paving ponds water, which softens the base and stains the surface. Every area needs a fall to a drain or a channel.
Check it: Ask where the water goes. The answer should be a direction and a channel, not a shrug.
Dimensional variation above ±3mm
Blocks that differ in size give ragged joints that never lock properly. KS 827 tolerances exist for a reason.
Check it: Measure five blocks with a tape. Length and width should agree within 3mm.
Quotes that hide what is included
Transport, murram, sand, labour and kerbs are each a real cost. A cheap headline price usually leaves one of them out.
Check it: Ask for transport, base work, kerbs and laying as separate lines. A total on its own tells you nothing.
The standard to hold everyone to
KS 827:2003 is the Kenya Bureau of Standards specification for precast concrete paving blocks. It covers compressive strength, dimensions and tolerances. You do not need to read it — but a supplier who has never heard of it is telling you something.
Then, whoever you buy from, work out the quantity yourself so you know what a fair quote looks like before you ask for one.
Questions on this
How can I tell machine-pressed from hand-moulded cabro?
Machine-pressed blocks have sharp, consistent edges, a uniform dense face and identical dimensions. Hand-moulded blocks vary in size, often have rounded or crumbly edges and can be scratched with a coin.
What is the 28-day rule?
Concrete reaches its design strength about 28 days after pressing. Blocks sold earlier are still curing and can chip during laying and compaction. Ask when the batch was pressed.
What is KS 827:2003?
The Kenya Bureau of Standards specification for precast concrete paving blocks. It sets the strength, dimensions and tolerances a block should meet. Use it as the benchmark when comparing suppliers.
How much should I order over the measured area?
Add 5–10% for edge cuts, breakage and a few spares for future repairs. 7% is a sensible default for a simple rectangle; go higher for curved edges or complex patterns.