Footings and Foundation
A traditional foundation method to support a structure in an area where the ground freezes
A footing is placed below the frost line and then the walls are added on top. The footing is wider than the wall, providing extra support at the base of the foundation. A T-shaped foundation is placed and allowed to cure; second, the walls are constructed; and finally, the slab is poured between the walls. Re-bars are tied and placed above the soil to reinforce concrete.
How It's Done: Footings and Foundations
Case Study: Strategic Homes Alignment
Strategic Homes Group Inc does:
- Isolated Spread Footing
- Wall Footing or Strip Footing
- Combined Footing
In summary:
- T-shaped foundations are used in areas where the ground freezes.
- First, the footing is placed.
- Second, the walls are constructed and poured.
- Lastly, the slab is placed.
Slab-on-Grade foundation
As the name suggests, a slab is a single layer of concrete, several inches thick. Under every house is a foundation, and under most foundations are footings. Most of the time we take footings for granted, and usually we can: For typical soils, a common 20–24-inch-wide footing can more than handle the relatively light weight of an ordinary house.
The slab is poured thicker at the edges, to form an integral footing; reinforcing re-bars strengthen the thickened edge. The slab normally rests on a bed of crushed gravel to improve drainage. Casting a wire mesh in the concrete reduces the chance of cracking. A slab on grade is suitable in areas where the ground doesn’t freeze, but it can also be adapted with insulation to prevent it from being affected by frost heaves.
In summary:
- Used in areas where the ground does not freeze.
- Edges are thicker than the interior of the slab.
- Monolithic (poured all at one time).
Frost Protected
This method only works with a heated structure. It relies on the use of two sheets of rigid, polystyrene insulation—one on the outside of the foundation wall and the other laid flat on a bed of gravel at the base of the wall—to prevent freezing, which is a problem with slab-on-grade foundations in areas with frost. The insulation holds heat from the structure in the ground under the footings and prevents heat loss from the edge of the slab.
In summary:
- Only works with a heated structure.
- Has the benefits of slab-on-grade in frost-prone areas.
- Concrete is poured in one operation (vs. 3 pours for T-shaped).
Helical Pier
A helical pier is a steel shaft with helices, similar to a large screw, that provides foundation support for various types of structures. The shaft is usually square and manufactured in 5-foot sections. Helical piers are often used when challenging soil conditions prohibit a traditional foundation system. They are also commonly used to correct and support existing foundations that have settled or failed.
The main function of helical piers is to support and stabilize the structure’s load-bearing walls by transferring the weight of the structure off weaker soils and onto the piers. One of the key benefits is that they can permanently lift a sunken foundation back to its original level.
Foundation
The masonry or concrete walls below ground level that serve as the main support for a structure. Foundation walls also form the sides of a basement area.
Foundation is one of the most important parts of the structure. It transfers the load from the building over a large area of soil, ensuring stability and minimizing settlement. The solid ground on which the foundation rests is called the foundation bed.
Foundation objectives:
- Distribute the weight of the structure over a large area of soil.
- Avoid unequal settlement.
- Prevent lateral movement of the structure.
- Increase structural stability.