Purpose of a Foundation
To provide a structure the building can safely transfer load to as to resist dead, imposed and wind loads.
To avoid settlement or movement that could cause instability or damage
Steps for Setting a Foundation
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- Mark space with corner profiles
- Use 3-4-5 method to attain corner squares
- Mark space for foundatios with profile boards
- Excavate
- Level
- Shore trenches
- Insert footing pegs
- Pour concrete into tenches
- Level and smooth the concrete to let dry
Foundations types
Strip
isolates/Pad
Raft
Pile
Derivatives of the Traditional Foundations
Cantilever
Ground Beam
Underpinning
Strip Foundations
- Used to carry long, continous loads
- Small buildings
- 1:3:6 (Cement; Sand; Stone)
- 200mm Maximum thickness
- 600mm Maximum length
- Can be reinforced with main and distribution bars
Steep, WIde, Narrow, Deep Types
Supported Walls by Strip FOundation
Cavity Wall
One Brick Wall
Half Brick Wall
One & A Half Brick Wall
Pad Foundation
- Used under point loads
- Square in plan wherever possible
- Constructed of reinforced concrete
- Width and depth depend on the conditions of the soil and the building’s bearing load
Types of Pad foundations
Mass Concrete Pad
Isolated Pad
Rectangular Pad
Combined Coloumn
Steel Grillage
Pile Foundation
- Where the strata closer to the surface level is at poor load-bearing capacity, so the building is made to rest on stable strata deeper into the ground
- Reinforcement may be sued to counter moevement of the ground
- Includes reinforeced conrete beam connecting the individual pile heads together
- Ground Beams may be placed ontop of pile caps
Types of Piles
End Bearing Piles (Firm Strata)
Friction Pile
Replacement Pile
Displacement Pile (Preformed Pile)
Pile Cap Ontop, Pile itself called a Pile Shaft
Raft Foundations
- USed to spread the load over the entire building area
- Can be used for light buildings
- Buildings with heavy loads atop poor, loose soils
- Where top 600mm of subsoil overlies a substrata of poor quality
- Concrete bed that covers the area of propsoed building
- Raft floats on the subsoil like water
Types of Raft Foundation
Reinforced Solid Slab
Reinforced Beam and Slab
Cellular
Cantilever Foundation
- Used to avoid placing pressure of load on adjacent foundations or underground services
