FOUNDATIONS
Function
The foundation is the base upon which the rest of the building shall rest; the foundation acts much like tyres in a car. Wobbly tyres cause instability in a car and can cause accidents; weak foundations cause buildings to collapse.
Unfortunately since foundations are hidden they tend to be taken casually sometimes with disastrous consequences.
Particularly for a storied building, you shall require a structural engineer to advice on design and supervise its construction.
Potential problems
- Limited skills
- Foundation laid on weak ground may cause building collapse
- Badly mixed concrete
- Poor design of foundation
- Contact with ground water in areas with high water tables
- Contact with soil with chemicals like sulphates
- Termite infested sites
Materials, plant labour requirements
- Cement
- Sand
- Aggregate
- Clean water
- Reinforcement steel bars
- Concrete mixer
- Vibrator
- Wheelbarrows
- Form work
- Masons and assistants
- Carpenters and assistants
- Steel fixers and assistants
Procedure for foundation works
Transfer the building from the drawing to the site (called setting out by pros).
Excavate soil up to good hard surface level.
Spray sides and bottom of the excavations with a termite destroying solution.
If the sides are not stable enough have them protected from collapse.
If necessary lay formwork to sides of foundations.
Lay blinding (weak concrete or sand) to protect the concrete from coming into contact with soil.
Lay spacer blocks to protect steel coming into contact with soil
Lay steel as necessary
Lay well mixed concrete foundation. Vibrate concrete to drive out voids and to achieve consolidation.
The concrete mix hardens over time. This process needs to be slow. This is achieved by continuously wetting the foundation concrete over about a week.
After this, substructure walling can start. Same for concrete columns including form work and vertical steel members.
