While footings help the foundation do its work, they’re some of the most underrated structural elements. A lot of homeowners believe the foundation is all that matters. But the truth is that the footings need to be healthy and stable as well. When building a house, footing construction should only commence after the soil conditions have been checked and the proper depth and width established.
If concrete footings sound foreign, we will help you demystify this structural element.
What Are Footings?
Each house rests on a foundation, under which there might be a footing. This structural element is formed using concrete and rebar reinforcement.
Footings provide support to the foundation in areas with active soils, where settling is a common problem. They can come in handy for projects such as retaining walls, decks, and pergolas.
Some of the common footing designs include stepped footing, spread footing, trench footing, and inverted “T” shape footing.
Strength, Depth, and Width
Footings vary in width depending on the site, soil conditions, and the structure being built. Building codes require that one-story buildings with footings on natural soils with load-bearing value (LBV) of 1,500 to 4,000 be 12 inches wide. Two-story buildings must have 15-inch-wide footings.
In stable soils, 16- to 20-inch-wide footings can adequately handle the weight of an ordinary house. Their depth will vary from place to place depending on soil strength and level of the frost line. In winter, they should extend 12 inches below the frost line or be frost protected.
For slabs and foundations, the minimum strength of the concrete should be 2,500 psi. Exposed vertical walls require a similar strength. If there’s severe weather in the area, this needs to be at least 3,000 psi.
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.
Things That Influence Footing Construction
When forming concrete footings, your foundation contractor will take a couple of things into consideration. And these include:
Different types of footings can sit on different soils. The type of soil around and beneath your footings and their condition will determine their strength and health.
Additionally, how the soil is compacted does play a vital role during footing construction, especially if the soil is transported from elsewhere and used as backfill. Loose soils can lead to settlement.
Before construction starts, ask a structural engineer to examine the soil on the ground and to determine whether it can adequately support your building. If the soil is active, they might recommend wider footings and additional support.
In the worst-case scenario, the soil must be dug out and replaced with stronger backfill. Your contractor can also mix the active soil with aggregate to enhance its bearing capacity.
The amount of moisture in the soil also determines the density of your footings. When the soil dries up, it tends to clump together, and this makes compaction difficult. If the soil gets soggy, its particles will break apart and this can lower its density.
Different layers of soil have different moisture levels and temperatures. And each layer behaves differently when your structural load passes through it. Make sure your contractor measures the soil moisture content onsite before they embark on construction.
Are Concrete Footings a Good Choice?
Yes, they are. Concrete footings provide adequate support for your house like anchors do to a berthed ship. Once in place, the footings prevent foundation settlement and protect your home from damaging forces and environmental loads. While that’s the case, not every structure requires a footing.
If you’d like to repair your foundation or check the condition of your concrete footings, contact the experts at Foundation Recovery Systems for a free inspection and repair estimate. We’ll tell you what ails your foundation and recommend the best fix.