Explaining a Concrete Footing
When it comes to how a home is built, it is easy for homeowners to confuse footings and foundations. Footings help the foundation do its work. Without these structures, the foundation won’t be as stable or sturdy as it needs to be to support the entire house.
What Are Footings?
Footings are structural elements that are typically made from poured concrete and reinforced with rebar. Each house rests on a foundation under which there is a footing, as required by the International Residential Code. Concrete footings are used to support the foundation and to stop it from settling.
When building the concrete footing, the bottom of the trench must be level while its sides must be straight. The dimension of any footing depends on the type and size of the structure being built. When placed properly, footings can provide adequate support to the foundation and to the entire house.
- Spread footing: Has a broader base that spreads the structure’s weight over a larger area than the load-bearing wall that it supports.
- Stepped footing: This type of footing is isolated and helps transfer the load from unstable to stable soils.
- Trench footing: Made from reinforced poured concrete, it’s the gold standard in foundation construction.
Additionally, footings are also suitable for other structures including decks, retaining walls, and pergolas. Building contractors also recommend footings in areas with expansive or shifting soils, as they are likely to cause foundation settlement and other damage.
How to Build Concrete Footings
Here’s how concrete footings are built:
- The soil is first dug up.
- Next, wooden formwork is set up.
- Concrete is mixed on a clean surface.
- Concrete is poured right into the formwork.
- Refill material or soil is brought to the site.
- The home’s foundation is compacted, and
- The concrete cures within a couple of days or weeks.
Factors That Impact Footing Construction
There is much more to constructing footings than digging and pouring concrete into wooden frames. Engineers and builders must also consider two important factors when constructing a footing.
Soil Type and Condition
Not all soil is the same. In fact, there are thousands of types of soil across the country and the world. But they all have the same three basic ingredients in common – clay, silt, and sand.
Different types of soil have varying properties that will react to the weight of the structure in their own unique way. For example, denser soils are preferable instead of lighter ones. Hence, it’s key to consider how it will react to the footing.
In construction terms, there are three different types of soil that a concrete footing will sit upon.
- Man-moved soil
- Backfill soil
- Native soil layers
To properly construct a footing, a structural engineer needs to be involved. They will assess and inspect the soil and come up with a solution. By considering its properties, a structural engineer will decide whether you’ll need to replace the soil with a new type. Other options include mixing the existing ground with added materials to improve its load-bearing capacities.
Another factor building contractors need to consider is soil moisture. This factor will determine the density of the concrete footing. If concrete is poured into a hole with dry soil, chances are that the soil will suck the water out of the concrete, and, as a result, the concrete will become much weaker than it is supposed to be. This is why it is important to dampen any dry soil before the concrete is poured.
However, all soils have different drainage properties and not all dry soils should be moistened the same way. For instance, sandy soils tend to drain water quite well, silty soils are likely to have intermediate drainage properties, and clay soils significantly expand and swell when wet and shrink when dry. That means excess water in the soil increases the water-to-cement ratio in the concrete and weakens the footing. Therefore, it is important to check the moisture content of the soil before any work is done.
The Pros and Cons of Concrete Footings
Concrete footings have numerous advantages, but the main ones that are also the function of this structure are to support and anchor the foundation, preventing the house from settling. Concrete footings are your first line of defense that need to withstand environmental loads and natural forces.
However, the underlying soil and local weather are forces that can significantly damage the footing, foundation, and your home. Soil that is too wet, too dry, or was not properly prepared during construction can shift. This shift can compromise your footings and leave the rest of the structure without the vital support it needs, resulting in various signs of damage. Concrete also can succumb to damage over time, even though it is a durable material.
How Professionals Repair Damaged Footings and Foundations
Different kinds of foundation damage are common, and some may point to problems with the concrete footing. The only way to know for sure is to have a free foundation inspection completed by an expert from your local Groundworks company. They will do a thorough evaluation of your home, accurately diagnose your foundation problems and the causes behind them, and then recommend solutions tailored to meet your home’s unique repair needs.
The footing is also critical during one of our repair processes. When we repair foundation settlement by installing pier systems like helical piers or push piers, we dig down far enough to access the bottom of the footing, drive the piers down to more stable, load-bearing soil, and attach heavy-duty brackets to the footing. This further enhances the piers’ capacity and the stability your foundation and home rely on.
For more information about concrete footings or how you can protect your foundation, contact Groundworks today to book a free inspection and estimate for the best fixes for your foundation.
The three most common types of foundations found across the country are basement, crawl space, and slab. While each one is constructed a bit differently, they all have a concrete footing to help give them a solid base. Even a crawl space, which typically has a dirt floor, is constructed by first pouring a footing and then adding foundation walls on top of it. There are other ways of constructing homes, however, including pier and beam foundations that are common in Texas. These foundations are similar to crawl spaces but are not enclosed.
While many footings are approximately one foot deep, the footing depth greatly depends on other building specifics like the number of stories and the strength and capacity of the soil. Engineers and builders also must consider factors such as the frost line, soil type, and water table in the area where the home is to be built.
As with footing depth, the weight a footing can support is dependent on many variables. These include how tall the home will be, what type of house it is, the materials used for construction and aesthetics, and the type of soil at the build site and its condition and load-bearing capacity. Builders will also consider the weight of people, furniture, and other contents.