What is beam and slab raft foundation?

What is beam and slab raft foundation?

Beam and Slab Type Raft Foundation Columns are situated exactly on intersections of beams of raft foundation. This type raft foundation is suitable when the columns are carrying unequal loads and there is large space between them.

Does raft foundation have beams?

Cellular raft foundation This type of raft foundation consists of two slabs with two-way interlocking ground beams. The upper (suspended) slab and the lower (ground bearing) slab are usually incorporated within the beams to form I-sections, with voids between them.

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 type of foundation is raft foundation?

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.

How deep is a raft foundation?

There are certain requirements that need to be considered during the of raft foundation in order to produce adequate design such as minimum depth of 50cm, required excavation depth of approximately 2.5m, and rebar cover of 50mm.

What is the minimum thickness of raft foundation?

What is the Minimum Thickness of a Raft Slab. In residential buildings, the minimum thickness of a raft slab is 85mm (3.35 inches) in waffle slab construction and 100mm (4 inches) in raft slab construction.

What is raft slab?

Raft slabs consist of a thick steel reinforced slab that is integrated with steel reinforced beams, which are dug into the ground for added strength and support. The depth and spacing of the edge and stiffening beams is dictated by the ground it is being constructed on.

What is the depth of a raft foundation?

How thick is a raft slab?

approximately 100mm thick
Raft slabs are approximately 100mm thick with thickened edges that can vary from 300-700mm. Things like water can cause these slabs to shrink when dry and swell when wet, meaning they require much deeper stiffening and edge beams to counter less predictable site conditions.

Why is it called a raft slab?

Put simply, a raft slab is cast atop the soil, like a raft on the water, with no other foundations piercing the ground into the subsoil. It is often implemented as an alternative to a pile foundation, which requires deep excavation.

What is the standard height of beam?

THE STANDARD SIZE OF THE BEAMS In a residential building it is 9 ʺ × 12 ʺ or 225 mm × 300 mm standard size according to (IS codes). The minimum RCC beam size should not be less than 9 ʺ × 9 ʺ or 225mm × 225mm with the addition of a 125mm slab thickness.

What is the minimum depth of raft foundation?

The minimum thickness of raft foundation is 300mm.

Are raft slabs more expensive?

Raft slabs and waffle slabs cost more due to their reinforcement and footings, with raft slabs usually being the more expensive of the two.

How is a raft slab built?

What is a raft foundation?

Raft foundation is a thick reinforced concrete slab which spreads over a large area of soil and provides support for several columns and load bearing walls. It is also called as mat foundation which are widely used foundation system. 1. Flat Plate Type Raft Foundation

What are the characteristics of a rim raft foundation?

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. They spread the load imposed by a number of columns or walls over the area of foundation,…

What is piled raft slab foundation?

In case of piled raft foundation, raft slab is supported by piles in soil. This type of foundation is preferred for soils of high compressibility and high water table. These are well suitable for high rise buildings.

What is the purpose of a raft beam?

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 .