How do you detail a raft foundation?

Key steps of Raft foundation construction are noted below.

1. Identify the desired depth at which foundation is to be provided.
2. Excavate soil up to the required depth.
3. Compact the soil.
4. Provide a waterproofing membrane.
5. Pour 3” of plane cement-sand paste.
6. Lay reinforcement maintaining the required spacing using spacers.

Does raft foundation have beams?

In case of Beam and slab type raft foundation, beams are laid in perpendicular directions and all of these beams connected by raft slab. Columns are situated exactly on intersections of beams of raft foundation.

How is the reinforcement laid for raft foundation?

Typically, a thickened reinforced area is created at the perimeter of the raft to form an edge beam supporting the external walls of the building. A concrete toe often supports the external leaf of the wall. Insulation will generally be laid on top of the raft, with a concrete floor, or raised floor above.

What is the minimum reinforcement in raft foundation?

The raft design will normally need a hardcore sub-base to level the ground. This stone should be mechanically compacted. You must ensure steel reinforcement is lapped at least 450mm (for both mesh and mild steel bars) and provided with 40mm concrete cover.

Is raft foundation deep or shallow?

Raft foundations are a type of shallow foundation. They are typically formed by reinforced concrete slabs that cover a wide area, often the entire footprint of a building.

What is piled raft foundation?

A foundation is described as ‘piled’ when its depth is more than three times its breadth (Atkinson, 2007). Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.

What are the disadvantages of raft foundation?

Disadvantages of Raft Foundation

• Raft foundation is prone to edge erosion.
• Raft foundation requires more amount of reinforcement in some cases, and it will ultimately cost more.
• Skilled labours are required as compared to other foundation.

What is the difference between raft and pile foundation?

Difference between raft and pile foundation The raft foundation or mat foundation is a prominent example of a shallow foundation. On the other hand, the pile foundation is an example of a deep foundation. This is one of the first and the most general point of difference between these two types of foundations.

What is minimum reinforcement ratio?

The minimum reinforcement ratio is the lowest possible quantity of steel that should be embedded in structural concrete elements to prevent premature failure after losing the tensile strength. The minimum reinforcement ratio controls the cracking of concrete members.

What are the three types of raft foundation?

There are five main types of raft foundation:

• Solid slab rafts,
• Slab beam rafts,
• Cellular rafts,
• Piled raft foundations; and,
• Balancing (or floating) rafts.

What kind of construction is a raft foundation?

This construction article provides the detail construction methods for raft foundation of a building. The raft foundation is conducted for the multistory buildings or building having heavy loads.

What is the bearing stress of raft foundation?

The raft foundation is a kind of combined footing that may cover the entire area under the structure supporting several columns in one rigid body. In this project, the soil profile shows that the bearing stress is around 100 kN/m2 . The raft foundation is usually used with this kind of soil. The columns have high axial loads.

When to start exaction on a raft foundation?

The raft foundation is conducted for the multistory buildings or building having heavy loads. Step 1: Initially, the surveyor should begin exaction and as soon as the survey is completed then exaction is carried out to the desired level on the basis of the validated shop drawings.

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.