## How is raft foundation made?

A raft foundation is constructed by first excavating the ground to a uniform, flat level. Then, a waterproof plastic sheet is laid over the earth, and a thin 3″ layer of plain cement concrete (PCC) is poured just to create a perfectly flat and level base for the foundation.

### What are the three types of raft foundation?

Types of raft foundation include:

- Solid slab raft, sometimes referred to as a plain raft, and including; flat rafts, mats, wide toe rafts, slip plane rafts, blanket rafts, and so on.
- Slab beam raft.
- Cellular raft.
- Piled raft.

#### What are the design approaches for raft foundation?

There are two methods for the design of raft foundations. They are: Conventional Method. Soil Line Method.

**What is the main reason for using 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 do you build a raft slab?**

Here’s the process for building a raft slab for a house.

- Step 1 – Set Out.
- Step 2 – Edge beams.
- Step 3 – Steel reinforcement for raft slabs.
- Step 4 – Edge beams filled.
- Step 5 – Sand fill.
- Step 6 – Excavate strip footings.
- Step 7 – Damp proof membrane.
- Step 8 – Slab reinforcement.

## What is the depth of 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.

### Which type of raft is commonly used?

Slab beam rafts This type of raft foundation is typically used in a build that involves column loads that are not evenly distributed across the footprint of the building. Reinforced columns are sited on top of reinforced ground beams, and this provides the necessary load bearing capacity.

#### How do you make a raft slab?

**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.

**How deep is a raft foundation?**

## Which soil is suitable for raft foundation?

Raft foundation is preferred when the clayey soil is compact and hard. Even strap foundation can also be used. Soft clayey sand is prone to expansion and shrinkage. They have a low bearing capacity and are unsuitable for footing and strap foundation.

### What is the minimum reinforcement in raft foundation?

That means for RAFT irrespective of thickness, we may need min 0.09% (of gross c/s) reinforcement on each face in each direction for 420 grade bar according to ACI 318-2011.

#### How do you size a raft foundation?

The dimensions of the raft should be at least 3m x 2m and the longer dimension should be less than 1.5 times the shorter dimension. Internal stiffening beams, similar to the internal edge beam may be required 6. The ground must be well consolidated and capable of supporting a load of at least 50kN/m². 7.

**How thick is a raft slab?**

100mm thick

The Raft Slab: This slab is usually 100mm thick with thickened edges varying between 300mm and up to 700mm deep. Throughout the slab there are also stiffening beams which are 300mm wide and vary in depth up to 700mm. These beams are spaced at a maximum of 6000mm to a minimum of 4000mm.

**Which foundation is best for construction?**

Basement Foundation. A basement is one of the best house foundations that typically has ceiling heights of 8′ and is often finished off as living or storage space.

## Where is raft foundation applicable?

Raft foundation is generally used to support structures like residential or commercial buildings where soil condition is poor, storage tanks, silos, foundations for heavy industrial equipment etc.

### How do you calculate reinforcement in raft foundations?

3 deflection calculation: The maximum deflection is considered as the deflection of three span continuous beams under uniform load, the calculation formula is as follows: ν max =（0.677q 1 +0.990q 2 ）l 4 /100EI; Standard value of static load q 1 = 1.800+1.500=3.300kN/m; Standard value of live load q 2 =2.700kN/m; the …

#### What is the depth of a raft foundation?

**Where is raft foundation used?**