What is the strongest foundation for a house?
The strongest foundation for a house is a plinth and beam foundation. Many people flock towards using a plain old-fashioned concrete slab foundation as it is cheaper to make and can be made by any contractor. But it is not the strongest type of foundation. In fact in areas where the soil is muddy or the soil is loose using a simple slab foundation can have many serious consequences.
The entire structure of the house is supported by just a slab of concrete. This slab is under constant load and shearing stresses. If the soil underneath the house caves in, slides, or shakes as can happen in the instance of an earthquake a slab foundation can break and the whole structure of the house will collapse with the roof falling over. So, in places with muddy soil or in areas that lie on the tectonic plates, where earthquakes are common a simple slab foundation should be avoided at all costs. You need to build something that lasts a few centuries rather than a few years.
However, one must always weigh the pros and cons of each foundation style before laying it down. There are three main types of foundations recommended in modern code worldwide. These include:
- Slab Foundation
- Plinth and beam Foundation
- Basement Foundation
A slab foundation is the cheapest while a basement foundation is the most expensive. Similarly, a basement and plinth and beam foundation is the most secure while a slab foundation is the most prone to crack and shear. So there are always benefits and drawbacks.
If you are building a single-storey house in an area where the soil test demonstrates the soil to be rocky or hard you can just put a concrete slab foundation and call it a day. In areas, where the soil test indicates muddy or porous soil under the plot of land going with a plinth and beam will be the best bet. Nowadays, modern code requirements of different areas will allow only certain types of foundations based on the soil test and geographical survey so you may be mandated to use a certain type of foundation.
That aside one must be aware of all the foundations and their hence I have included details on all these types below. You should also consider checking my article on ways to build the foundation of a house.
Table of Contents
What is a plinth and beam foundation?
The plinth and beam foundations are made by digging trenches right under the proposed walls of the house. The trenches are then blocked with shuttering. Shuttering is basically the instalment of wooden walls that can contain the concrete while it is freshly poured and is liquid. The shuttering allows a homogenous as well as a solid block pour of concrete into the trenches. This has two-fold importance:
Importance of shuttering
- Concrete is poured into premade shuttering walls that contain the concrete and give it the shape of a rectangle. This prevents concrete from being poured into the non-uniform trench which can lead to structural problems
- Secondly shuttering allows to build the base of the plinth beam wider and subsequently reduce the size of the plinth pillar as you come up to the ground level from the trench depth. This can save a lot on the amount of concrete required for building the plinth beam foundation
How is the foundation reinforced?
The foundation is then reinforced with steel bars and wires aka sarya or iron threads. This is exactly what the proverb says reinforced concrete with steel bars. Reinforcing the concrete used will aid in its weight-bearing ability and will give immense support and flexibility to the concrete columns aka plinths. This aids in earthquake-proofing of a brick and mortar house. Many people try to use low-quality steel rods which are either too thin or are made of cast iron.
Be advised I would strongly advise you to stay away from all such wrong advice. Using iron instead of steel will make the bars prone to rusting and as concrete is generously sprayed with water after it sets to enhance the chemical reaction occurring in concrete the iron in the bars runs a risk of rusting. The rusting can also occur if your house is built on lands that have groundwater level that is very close to the surface. Also, be advised that using thin steel bars will reduce the strength of the structure as thin steel bars can bend easily, and your house runs the chance of being prone to earthquakes.
Alternatives to plinth and beam foundation
A basement foundation is one of the most commonly employed alternatives to plinth and beam foundation. The walls of the basement are made using the same plinths and beams but instead of filling the structure and trenches up with dirt, they are left open. You may need to fill in the dirt that surrounds the basement in order to meet the housing market code requirements.
Making a basement though will add a lot to the overall cost of the project. As basements are made entirely of reinforced concrete the cost tends to rise quickly and steeply.
Slab foundation with plinths
This is another alternative but it is only allowed in certain localities and is banned in others. This is a more sophisticated version of a simple slab foundation. Basically, the simple slab foundation is reinforced by building three or more points underneath it. This type of structure can then provide enough rigidity to support a double-story house if it is made up of wood. But it will not be allowed for double-storey houses made of bricks.
Finally, before you click off do check out my article on ways to build a foundation for a small house here. You should also check out the book, “The complete visual guide to building a house “. It is the one I used while I was building my own house. It contains all the important details in full detail so you don’t get trapped by your contractor.
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