Raft foundation / Mat foundation
Sheet under review by our engineersIt's a large reinforced concrete slab that covers the entire footprint of your future house. Instead of individual foundations, it's as if the whole house rests on a single, thick concrete 'mat'.
Why it matters for your home
Ideal for unstable or soft ground, as it spreads the house's weight over a very large area. It's also very effective if you're in an area where the ground might shift (like a flood zone) or to prevent rising damp.
The African context
Increasingly used in urban areas where land quality can vary, or in marshy or flood-prone zones. Its installation requires good expertise and significant rebar, which is often overlooked.
Red flags
- ⚠ The ground is not properly leveled and compacted before placing the raft foundation rebar.
- ⚠ The rebar is not supported by spacers and rests directly on the ground.
- ⚠ The concrete poured is of poor quality (too much water, not enough cement) and the raft is thin.
Questions to ask
- 1. "Why did you recommend a raft foundation for my land?"
- 2. "How will drainage be managed around the raft to prevent moisture?"
- 3. "What is the exact thickness of the raft foundation and the rebar plan?"
Cost hint (indicative)
More expensive than footings, approximately 8,000 to 20,000 FCFA per m² on the ground, just for the raft slab, before the compression slab, and excluding significant earthwork.
Related terms
At this stage of your project?
An independent DiasporaBuild inspector can verify on site before you pay.