This is an ultimate guide to different types of foundations used in civil construction.
In this guide, you’ll learn:
- What is a foundation?
- How does foundation work?
- Why foundation is provided?
- Why various types of foundations are designed?
- Different types of foundations used in civil construction.
Let’s dive right in.
What Is A Foundation?
Simply saying, a foundation is the most bottom part of a structure.
Typically, the main function of a foundation is to transfer loads imposed on it to the soil.
Besides this, a foundation does some other works:
- Prevent lateral movement of the structure
- Increase structural stability
- Minimize differential settlement
Why Different Types Of Foundations Are Designed?
Mainly, which type of foundation will be provided to a structure depends on the bearing capacity of the sub-soil.
But, the following factors are also considered:
- Type of structure
- Structural loading
- Economical factors
- Time factors (relative to the proposed contract period)
- Construction problems
With that, let’s see the…
Different Types Of Foundation
Basically, there are two types of foundation:
- Shallow foundation, and
- Deep foundation
This type of foundation is often called Footing.
And it’s designed when the subsoil condition is good.
Generally, when the width of the entire foundation is greater than its depth that is considered as a shallow foundation.
Normally, they are embedded about a meter or so into soil.
In comparison to deep foundations, shallow foundations are:
- Less technical
- More economical, and
- Widely used
Types Of Shallow Foundation
The following are the different types of shallow foundations:
- Isolated footing
- Combined footing
- Strip footing
- Mat footing
This type of foundation is designed when the subsoil near the surface is poor and unable to carry the structure’s loads.
With this foundation, the load is transmitted to the deeper level of the soil.
Types Of Deep Foundation
Basically, there are three types of deep foundation:
- Pile foundation
- Pier foundation
- Drilled Shafts or Caissons
With this, now you’ll learn about the different types of foundation and their uses below:
- Individual footing
What It Is?
This foundation is designed to support single columns.
And it’s the most economical foundation.
When It Is Designed?
- If the loads on footing are less.
- If two columns aren’t nearby.
- When the soil bearing capacity is high.
Types Of Isolated Footing
- Pad footing
- Sloped footing
- Stepped footing
What It Is?
Basically, this footing is a combination of two or more isolated footings.
When two or more columns are very near to each other then this type of footing is designed.
Combined footings can be rectangle or trapezoidal.
When Combined Footing Is Used?
- If two columns are near to each other and their footings overlap.
- If the soil bearing capacity is relatively lower.
- When one column is closed to the property line.
- If the Dimension of one side of the footing is restricted.
Types Of Combined Footings
Following are the types of combined footings:
- Slab type
- Slab and beam type
- Strap beam type
Read the details of these types of combined footings here.
- Wall footing
- Spread footing
- Continuous footing
What It Is?
This footing runs along the direction of the wall.
Generally, the width of this footing is 2-3 times the width of the wall.
And, stone, or bricks, or reinforced concrete is normally used to construct this type of footing.
To know more about this footing visit: All About Strip Footing
- Raft footing
What It Is?
This shallow foundation is spread across the entire area of the structure.
It carries the entire load of the superstructure and spreads it over the whole area.
When It Is Used?
This foundation is used:
- When the loads are very high
- To prevent differential settlement of individual footing.
- If the soil bearing capacity is less.
But Mat foundation shouldn’t be used where the groundwater table is above the bearing surface of the soil.
Types Of Mat Foundation
- Flat plate mat
- Plate thickened under columns.
- Two-way slab and beam
- Piled mat
- Rigid frame mat
To learn more about this type of footing, read my comprehensive guide on mat foundation that I’ve published recently.
This is a type of deep foundation.
And, it is designed to transfer loads to the deeper level of the soil.
When This Foundation Is Used?
- If the bearing capacity of soil near the surface is relatively low and isn’t suitable for heavy loads.
- When the hard rock strata is at least 15 feet below the ground surface.
- When it is very expensive to provide raft or grillage foundation.
- If there are chances of construction of irrigation canal in the nearby area.
- When the foundation is subjected to a heavy concentrated load.
- In marshy places.
Types Of Pile Foundation
Based on materials:
- Concrete piles
- Timber piles
- Steel piles
- Composite piles
- Sand piles
Based on function or use:
- Sheet piles
- End bearing piles
- Friction piles
- Tension piles
- Batter piles
- Fender piles
- Compaction piles
Based on Installation Methods:
- Driven and Cast-in-situ piles
- Bored and Cast-in-situ piles
- Screw piles
This type of foundation is like the pile foundation.
But, unlike piles, it can only transfer loads by bearing, not by skin friction.
And it is a cylindrical structural member.
When Pier Foundation Is Designed?
- If sound rock strata is under a decomposed rock layer at the top.
- When the topsoil is stiff clay which resists driving the bearing pile.
Types Of Pier Foundation
It may be two types:
- Masonry/concrete pier
- Drilled caisson
- Drilled shafts
What It Is?
This type of deep foundation is constructed above ground level.
And then sunk into the ground to the desired depth.
And then filled with concrete.
When This Foundation Is Designed?
Generally, it is designed for structures that require foundations beneath a river or similar water bodies.
Types Of Caisson Foundation
- Box Caissons
- Floating Caissons
- Pneumatic Caissons
- Open Caissons
- Sheeted Caissons
- Excavated Caissons
If you don’t understand the difference between the different types of deep foundations, read this:
Now It’s Your Turn:
So, these are the different types of foundations.
And I hope this post helped you to understand different foundation types.
In my 20 years in the construction field, I didn’t have the luck to construct all of these foundations.
Such as I didn’t work in pier foundation and caisson foundation.
Now I’d like to hear from you:
Have you worked with all of these types of foundations?
Maybe you haven’t worked with some footing types?
Either way, let me know by leaving a comment below right now.