What is strip raft foundation?
Strip foundation is used to support a line of loads such as load-bearing walls. Raft foundation consists of a concrete slab which extends over the entire loaded area so that loads from entire structure are spread over a large area leading to a reduction of the stress of foundation soils is reduced.
How does a raft foundation differ from a strip foundation?
Unlike the strip foundation, raft foundations are used where the ground may be stable, but the bearing capacity is low, like boggy land, wet ground or where soils have been imported to site. Concrete for raft foundations is poured over the total area of the house, making it look like one big concrete slab.
Is Strip foundation cheaper than raft foundation?
Most of the architects prefer the strip foundation over the raft foundation, and in the public consciousness is that the strip foundation is cheaper. We think that the price difference is not significant, we illustrate it with an example, and we would like to help you out to make a better decision.
Is Strip foundation expensive?
Deep Strip foundations are the least expensive and are used when ground conditions are good. A concrete strip, sometimes reinforced with steel mesh, supports the walls. The trench depth is variable but in most cases should be at least 1m with a width of 600mm.
Why would you use a raft foundation?
A raft foundation is a reinforced concrete slab under the whole of a building or extension, ‘floating’ on the ground as a raft floats on water. This type of foundation spreads the load of the building over a larger area than other foundations, lowering the pressure on the ground.
How thick should a raft foundation be?
150 mm to 300 mm
Raft foundations (sometimes referred to as raft footings or mat foundations) are formed by reinforced concrete slabs of uniform thickness (typically 150 mm to 300 mm) that cover a wide area, often the entire footprint of a building.
What are the advantages of raft foundation?
Advantages of Raft Foundation
- Raft foundations are constructed for shallow depths hence, it requires less excavation.
- Well suitable in soils of low bearing capacity.
- Loads coming from superstructure are distributed over a larger area.
- Differential settlement of soil can be reduced.
How thick is a raft foundation?
How do you pour a raft foundation?
How Do Raft Foundations Work?
- The soil removed down to correct depth.
- The foundation bed is then compacted by ramming.
- Lay reinforcement on spacers over the foundation bed.
- Pour the concrete over the reinforcement.
When to use a raft foundation for a building?
As a rule, raft foundation is used as a building’s foundation when the soil has a low bearing capacity. The behaviour of the raft foundation resembles the behaviour of a strip foundation grid. The stresses applied on the soil are larger in the columns area and smaller in the intermediate areas.
Which is a stiffener in a ribbed raft foundation?
In a ribbed raft foundation apart from the unified foundation slab there are also beams which behave as stiffeners. The beams add stiffness to the foundation and they also level the soil stresses.
Is the column rebar independent of the raft foundation?
In the latter case, the reinforcement of the foundation slab does is independent of the wall’s reinforcement. The column rebars are in grey color. In the solid raft foundation, there is only one unified foundation slab.
What is the thickness of a raft footing?
(sometimes referred to as raft footings or mat foundations) are formed by reinforced concrete slabs of uniform thickness (typically 150 mm to 300 mm) that cover a wide area, often the entire footprint of a building.