Most building failures in Kenya don’t happen because of the roof or walls — they happen because the foundation was done wrongly. If you get the foundation wrong, the entire structure is at risk. Sadly, this is where many unqualified contractors and quacks cut corners.
To help you avoid costly mistakes, here are the 10 most important things you must pay attention to during foundation construction:
1. Proper Site Analysis
Before you even start digging, understand your site. Check the soil type, drainage, and slope. Some soils (like black cotton) require extra reinforcement, while sloping land may need retaining walls. Skipping site analysis can lead to cracks and instability.
2. Excavation Depth
Your trenches must be deep enough for stability. For a bungalow, dig at least 450mm (1.6 feet), while a one-floor building needs at least 900mm (3.6 feet). Ensure you reach firm soil at that depth to support the structure.
3. Foundation Concrete Casting, Not Mortar
Mortar is not concrete. Always cast the foundation trenches (blinding) with proper concrete before laying blocks. Laying blocks directly on soil with mortar is unsafe and weakens the entire building.
4. Foundation Height and Flood Protection
Your foundation should be high enough to prevent floodwater from entering. Study the flood history of the area and nearby houses before setting your height — don’t just depend on road levels.
5. Damp Proof Membrane (DPM)
Install a quality DPM nylon sheet between the foundation and floor slab to stop water from penetrating into walls and floors. Without it, you’ll deal with dampness, peeling paint, and mold.
6. Material Quality and Durability
Your foundation must withstand heavy loads for decades. Use high-quality cement, sand, ballast, and reinforcement steel. Cheap materials may save money now but will cost you much more in repairs or rebuilding later.
7. Accuracy in Measurements
Mistakes at the foundation stage carry through the entire building. Ensure precise alignment, squareness, and depth. An inaccurate foundation will affect walls, doors, windows, and even roofing.
8. Soil Compaction and Backfilling
After laying the foundation, proper compaction of backfill material is crucial. Loose or poorly compacted soil causes sinking floors, cracks, and weak support. Always compact layer by layer.
9. Adequate Curing of Concrete
Concrete gains strength over time, but only if cured well. Keep the concrete moist for at least 7 days to allow proper hydration. Poor curing weakens the structure and reduces durability.
10. Engineer’s Input for Multi-Storey Buildings
If you’re building more than one floor, always involve a structural engineer. They’ll analyze the soil and recommend the right depth and type of foundation (strip, raft, or pile). Never rely on guesswork for multi-storey buildings.
Final Note: The Foundation is Everything
A roof keeps you dry, but the foundation keeps your building alive. Cutting corners at this stage is like building a house on sand — a disaster waiting to happen. Always work with qualified experts, use durable materials, and follow the right processes.
Strong foundations = Safe homes = Secure investment.
