Types of foundations found in construction projects
Whether building single-family homes, skyscrapers or superstructures, choosing the right foundation is essential. The foundation of a building serves two main purposes: to distribute the weight of the load-bearing walls to the soil or bedrock below and to keep out groundwater or soil moisture.
The topography, geology, and soil science (the study of soil) at your construction site and the size of your building, and other factors, such as the type of construction, determine the type of foundation that is right for your building.
In this article, we’ll cover the most common foundation types and examples of each. We also provide visual evidence of each foundation to clarify the benefits of each type of foundation as well as professional patio installation examples when using a foundation-based approach to the concrete slab.
What are the types of foundations?
Since the land beneath our feet can be made up of many different types of soils, rocks, sediments, and more, geotechnical engineers need to understand how these variables within the earth affect its structure and structural integrity.
There are two main categories of foundations in construction: deep and shallow. Let’s cover them at a high level:
Deep foundations are required when building on sand and other soft soil that cannot support the load of the building. Instead, a foundation must be built deep underground or even underwater, where stronger strata can be established.
Bridges, piers, and dams, for example, must provide foundations underwater while preserving structural integrity, and this is where deep foundations become essential for the construction of large structures.
Usually, a shallow foundation is wider than a deep, and shallow foundations can also be called staggered or open foundations.
For obvious reasons, shallow foundations are the more economical of the two types, and they don’t require much digging or drilling into the earth, and for that reason, they are the most common.
Shallow foundations are useful if the building is not extremely heavy and the ground at a shallow depth can support significant weight.
Examples of shallow foundations
We will cover four examples of shallow foundations: slab, individual foundation, combined foundation, and trunk wall. Each has a unique structure and different usage scenarios.
A slab foundation makes the most of the surface where the building will be erected, essentially using the basement as the entire load-bearing foundation. Mat foundations are often used when the soil is loose and weak, and the weight needs to be evenly distributed.
Mat foundations are also used when a basement is feasible, and the pillars or columns are close together. It is often called a raft foundation because the basement foundation is submerged in the ground like the hull of a raft in the water.
One of the most common types of shallow foundations is the individual foundation – it may even be what comes to mind when you think of a foundation.
Individual or insulated staggered foundations are usually square, rectangular, or even a geometric truncated block of concrete that bears the load of a single column or pillar. The width of the individual foundations depends on the weight being carried and the bearing capacity of the soil.
A combined foot is very similar to an individual foot, except that one foundation shares the weight of two pillars or columns that are close enough to warrant a shared foundation point.
Tribal Wall Foundation
A wall, strip, or continuous foundation is a foundation that runs the entire length of a load-bearing wall. The strip foot is usually two or three times the width of the wall in question and is usually constructed with reinforced concrete.
These foundations are typical when the weight of the building is distributed over load-bearing walls rather than columns, pillars, or beams. Strip foundations are often used for building masonry walls but can also be used effectively when building on gravel or densely packed sand.
Examples of deep foundations
Deep foundations are more commonly used for larger structures but can also be used for homes built on cliffs, over water, on the beach, or in other unique locations. Deep foundations are built right where they sound – deep in the earth. The main examples, pile, and caisson, also have some subtypes, which we will also cover.
The most common under the category of deep foundations is the pile foundation. There are two types of pile foundations: end bearing and friction piles, and both consist of drilling large, sturdy columns deep into the ground.
End bearing piles
Sometimes the soil we build on will never bear enough weight for the project’s size, even with dirt compactors and shallow foundations. Instead, we have to bypass this soft ground layer and move to the bedrock beneath it to distribute the load.
End-bearing piles are driven as deep into the ground as necessary for the end to contact the rock layer in the earth. This allows the load to be guided through the post and into the rock, providing safe weight distribution.
Friction piles take a different approach to the warring layer of soft soil. Rather than drilling down to the rock layer, the principle behind friction piles is an exchange of forces with the soil surrounding the column, making full use of the column’s surface area.
The amount of weight a friction pile can support is directly proportional to its length. Each stack has a zone of influence and must be distributed consistently to ensure even weight distribution and absorption. Poles can be made of wood, concrete, or H-shaped steel.
Poles can be prefabricated and driven into the ground or cast on-site (cast in place on-site).
A caisson foundation is usually used to construct a bridge, pier, or other structure above water. But it can also be used to support highway overpasses, houses on hills, and more. Caissons can be prefabricated, driven to the drilling site, and placed in a dredged well. Caissons can also be built on-site with a reinforcement mesh grid filled with concrete.
The loose land is excavated with an auger until the bottom is reached to build a caisson foundation. A hollow steel housing can be implanted during excavation to prevent the sand or soil from collapsing on the progress. The reinforcing bar is then centered in the casing, and concrete is poured, starting at the bottom and backfilling the casing, pushing the remaining groundwater upwards. When the concrete is sufficiently filled, the casing can be removed.
There are a few variations of the caisson; here are the main types:
- Open caissons: A box sunk into the ground with no bottom and stabilized with weights for ballast and a manure pipe to drain excess groundwater. The pressure chamber makes it possible to work indoors.
- Pneumatic caissons: When maintenance work needs to be done deep underground or underwater, these caissons are built to let workers into the shaft.
- Monolithic caissons: large single-column reinforced concrete caissons.
- Sump caissons: Caissons with the ability to pump water from below. Often used by offshore oil drillers to recirculate contaminated water.
- Baking caissons: A hollow concrete box with bottom and sides are submerged and filled with concrete. In its hollow state, the box is less dense than water and runs the risk of floating out of position, but it is more permanent once filled.
Choosing the right type of foundation
Depending on the size, location, and geotechnical challenges your project faces, the decision to build shallow or deep foundations may be straightforward. Still, the exact type of foundation may be more nuanced. Given the importance of a building’s foundation to its overall structural integrity, making this decision right is essential.
Use qualified construction companies, engineers, and consultants to verify that the foundation is solid and will support the load for the entire life of the structure. You also need to ensure that the lines of communication between all those involved in the project are clear. We also talked about Historical Fiction Buildings from books.