Hardcore / Compacted aggregate base
Sheet under review by our engineersIt's a layer of crushed stones or coarse gravel, well compacted, placed at the bottom of the foundations or under the ground floor concrete slab. It's like a solid 'backfill'.
Why it matters for your home
It ensures effective drainage to prevent capillary rise of moisture and insulates your house from the ground. It also provides a solid and stable base for your future floor slab, preventing localized settlement and cracks.
The African context
Very important in our humid climates to combat moisture and termites. Often replaced by sand or uncompacted construction waste, which is a major source of moisture problems and slab cracking.
Red flags
- ⚠ The contractor uses poor quality soil or rubble instead of crushed stone.
- ⚠ The hardcore is not compacted at all; you can easily walk on it and sink your foot in.
- ⚠ There is no polythene film (black plastic) laid on the hardcore before the slab.
Questions to ask
- 1. "What type of stones will you use for the hardcore?"
- 2. "How will you ensure the hardcore is properly compacted?"
- 3. "Will there be a damp-proof membrane (polythene film) over the hardcore before the slab?"
Cost hint (indicative)
Around 2,000 to 6,000 FCFA per m² for a 20-30 cm layer, excluding material cost (crushed stone).
Related terms
At this stage of your project?
An independent DiasporaBuild inspector can verify on site before you pay.