How to choose the type of foundation for your House Construction in Kochi?
Are you planning for a house construction in Kochi? Would you like to know the critical factors that may affect your construction? Do you know what the most important decision you might have to take before the construction begins? Then read on….
Choosing the right type of foundation is the critical step in your house construction in Kochi, Kerala.
Do you know why?
The strength of the house, the number of storeys that can be accommodated, and the ideal roofing entirely depends on the foundation. At Viya Constructions, we believe that foundation forms the skeleton of the house.
Our experience has taught us that the type of Foundation to be laid is actually determined by the kind of soil and the strata below the ground. We decide on ideal foundation for your site by analysing two strong parameters – weight of the building and the strata.
Factors that decide the type of foundation for your house
Firstly, the building weight is estimated, which can be summed up as the number of floors to be constructed, the number of slabs to be built over it and the load it has to take (this includes both live loads and dead loads). The foundation has to be strong enough to hold the entire weight of the building.
Secondly, the Strata – that include the soil condition of the ground and what lies below the top soil, is assessed. The characteristic of underground soil, especially its strength to hold the weight of the proposed house is critical for the foundation. This factor becomes especially important in the case of house construction in Kerala.
To assess the soil capacity, we do a soil test. This includes digging up of a hole on the ground to check what type of material is there (sand or clay or rock) and how much strength it can hold. Rocks can withstand more strength, followed by sand which has higher strength, when compared to clay.
Strong strata like rock can endure the entire weight of the building. But rocks are not available everywhere and it is highly likely that your site needs some reinforcement. To strengthen the strata and distribute the load, different types of foundations are used.
Types of foundation used in Kerala
The different types of foundations normally used in house construction in Kochi, Kerala are primarily categorized as 4 –
- Rubble Foundation
- Pillar Footing Foundation
- Raft Foundation(Strip Foundation) &
Let’s look at each of these in detail.
1. Rubble Foundation
A Rubble Foundation runs exactly beneath the layout of main walls of your house. Large rock pieces are used in a stepped manner to make rubble foundation. To construct it, firstly a minimum of 2 feet depth trench is made on the ground and rubble (hard rock) is skill fully packed there. The rubble is tight packed so that the gaps in between are minimum.
Sometimes, according to the soil condition, sand filling is done in between the rubble. For stronger foundation, Rubble packing with cement using ‘cement mortar joint’ on the top of a PCC (Plain Cement Concrete) is used.
The next step in Rubble foundation is a basement that is made over the rubble structure. Basement covers smaller area than the Rubble layer beneath. The basement area is determined by the distribution of load. For example, the thickness of the wall is normally 20cms. And the weight of the wall cannot be transferred directly to the ground at 20 cms. To distribute the load of the wall more area is created, making the basement 45 cms wide.
And normally a belt is provided over the rubble foundation to protect the building from differential settlement. That is, the small load variations over the ground in different areas, or strata variations below the ground will be taken care of by this.
2.Pillar Footing Foundation
Pillar Footing Foundation is ideal for high rise buildings with more than two storeys. In this type foundation, pillars are provided on the corners of the walls and footing (made of concrete) is given on the bottom of each pillar.
The weight of the pillar is hence distributed to the ground below using a larger base. For example for a 20-30 cms diameter pillar, a footing basement size of around 150×150 cms is used so that load is transferred and distributed.
After constructing the footing, these pillars are connected to make the plinth beam. Plinth beam takes the load of walls. Moreover, beams are used for roofing, and the weight of the concrete slab of roof is supported only by beams.
For residential house construction in Kochi, Pillar Footing is not much economical when we consider the overall cost of the building. Because of which, we recommend this for high rise commercial spaces than residential ones.
3.Raft Foundation (Also called as Strip Foundation)
For marshy land or loose soil, Raft Foundation is the best. Before placing the foundation, it is necessary to strengthen the soil beneath. The strengthening of soil is done by a process called sand piling. In sand piling, sand is pushed below a layer of clay with pressure. This layer is tightened in such a way that the land can withstand heavy load and distribution
of weight is even at layer below the foundation. Raft foundation also features a basement, constructed entirely with concrete below the walls. This is constructed in inverted T shape so that the load of the wall and is distributed to the bottom part of T.
We at Viya Constructions specialize in the Raft Foundations and we do it with utmost care for most of our house construction in Kochi. Coming to the cost, considering the overall cost of the building, Raft Foundation is economical than Pillar Footing, but definitely expensive than Rubble Foundation.
4.Piling or Pile Foundation
Pile Foundation is used when the soil below is of the least quality. Our engineers put it in simple words as “Piling is like piercing screw in to the land, by digging a hole and inserting the materials”. Pile Foundation is of two types – Under Reamed piles and Direct Mud Circulation piles (DMC piles).
Under Reamed Piles
Under Reamed Piles uses friction of soil and hence also called as Friction piles. For friction piles, holes are dug and the side walls are strengthened with chemicals. Steel rods are inserted to this hole and concrete is added. The friction produced by side walls of the hole and surface area of pile, keep the pile strong.
In DMC piles, the piles are positioned on the top of a rock beneath the soil. The land is pierced till rock is found. The pile is anchored to the pierced rock and steel structure is inserted to be concreted.
In both under reamed and DMC piles, on an average PSI, 25 to 30 piles are constructed for a 2000 to 2500 square feet building. Once piles are constructed, Pile caps are made over it. Pile cap transfers the load to the main building structure from the pile.
Piles are usually made on every corners of the room. A large beam called grade beam, runs over connecting all piles to distribute load between the piles. This ensures that any differential settlement among the piles will be accommodated by the beam and is distributed with the entire set of piles. For pile foundation, it is not necessary that the pillars have to continue till the top. Walls are generally constructed over the grade beams.
In a nutshell, foundations add strength to the soil beneath so that it can withstand the load of the house. On a cost comparison, rubble foundation is the cheapest one, then pillar footing, then raft foundation, then under reamed piles and then DMC piles. With the immense number of projects undertaken so far, our experience is that Raft Foundation is more economical than Piling and Pillar Footing when the overall structure of the building is considered.
Extra care for the foundation at Viya
The foundation that involves beams like Raft, Pillar Footing and Pile Foundation requires something more. The top of the beam need a brick work or a rubble filler work to fill the gap between plinth beam and the finished floor. We do a plastering of the inside walls of these brick construction avoid water seeping in through the bricks to the floors on the top.
This small brick wall will hold the land within foundation which is then layer filled with soil. We take immense care to ram the soil in layers of 15 cms, water it well and pack it to give a solid foundation for your house. Your house built over this foundation will last for at least two more generations.
Getting the foundation right is a complex process. And your dream of building the perfect house will not give you nightmares if you entrust it on experienced builders.
If you are considering options for a house construction in Kochi, we at Viya Constructions are ready to help you with the best building options.
Contact us now to make it a real dream home!