The Foundation of Construction: A Guide to Building Code Foundation Requirements


Building a home, or any structure, requires careful planning and adherence to building codes. One of the most critical aspects of construction is the foundation. The foundation is what supports the entire structure, and it must be built to withstand the weight of the building, and at the same time, it needs to resist movement caused by soil expansion, contraction, and settling. In this article, we will provide an overview of general building code foundation requirements and discuss Insulated Concrete Forms (ICFs) as a better option for a strong, long-lasting structure.

Building Code Foundation Requirements: A Complete Guide

What is the Foundation of a Building?

The foundation of a building consists of two basic components: The footing and the foundation wall. The foundation wall transfers the load from itself and the structure that rests on it, to the footer. The footer then transfers the load to the earth.

The Footing

The footing is the base of a building that provides stability and support for the entire structure. It is typically made of concrete and is designed to distribute the weight of the building evenly across the ground. Without a solid footing, a building can sink or shift over time, which can lead to structural damage and safety hazards. All footings must bear on undisturbed soil.

Foundation Walls

A foundation wall is typically a solid wall that is attached to the footing and rises to ground level at the point where the ground is highest, under the building. The wall can be made of materials such as lumber, cast-in-place concrete, concrete blocks, or Insulated Concrete Forms (ICFs). The thickness of the foundation walls will vary depending on load requirements and soil conditions. These factors are generally determined by an engineer.

General Building Code Requirements

Every construction project has its own specifications, and local codes have rules for foundation footings. Generally speaking, most code authorities use the 2018 International Building Codes (IBC) and 2018 International Residential Codes (IRC) as their guiding standards and they can modify them to comply with regional regulations or special conditions.

Depth of Footings

Footings should extend to a minimum of 12 inches below the previously untouched soil and continue down to at least twelve inches below the frost line or be encapsulated in frost-protection.

Width of Footings

Minimum footing width requirements in the U.S. depend on a variety of factors, including the type of construction, soil conditions, and local building codes. Always check the soil type in the design of footings. For example, according to the International Residential Code (IRC), a minimum footing width of 12 inches is required for most one- and two-story buildings. The width of the wall footing is generally 2-3 times the width of the wall.

Reinforcing Steel

According to the U.S. building codes, the minimum rebar requirements for footings vary depending on the size and type of the structure being built. Generally, a minimum of two #4 bars are required for residential footing. The rebar should be placed in a grid pattern with a spacing of no more than 18 inches apart. It is important to follow these minimum requirements to ensure that the footing can withstand the weight and pressure of the structure above.

Commercial building footings must meet minimum rebar requirements for reinforcement as well as concrete coverage over the bars. For #6 bars and larger, a minimum of 2 inches of concrete cover is required, while #5 bars or smaller require a minimum of 1½ inches. Vertical dowels are embedded in the footings to provide a lateral support connection for the foundation walls against the backfill forces of the below grade walls. These vertical dowels, 16" to 24" high above the footing are typically #4 or #5 spaced at 4' apart around the perimeter.

Foundation Wall Code Requirements

Typical foundation walls are erected on top of the footings or a concrete slab that rests on the footings, and will be made of either lumber, concrete, or masonry blocks.

All foundation walls are engineered based on the footing they sit on and the load that will be carried by them from the structure above. Modern construction techniques typically use poured concrete for the foundation walls, but there is a better alternative that provides strength, energy efficiency, durability, and contributes toward net-zero designation: ICFs.

Insulated Concrete Forms (ICFs)

Insulated Concrete Forms (ICFs) are an excellent option for building foundation walls.

They consist of two layers of foam insulation that are connected by plastic or metal ties to create a hollow space in between. The hollow space is then filled with concrete, for a strong and durable foundation wall that is also highly energy-efficient. ICFs provide superior insulation compared to traditional concrete walls, by reducing heating and cooling costs and providing a more comfortable living environment.


ICFs are reinforced concrete walls which are much stronger than regular poured concrete or concrete block (CMU) foundation walls. This allows for ICF foundation walls, in some areas, to be thinner than poured concrete or CMU walls. Engineering tables (IRC) for below grade walls show that an ICF 6" concrete core meets most applications for below grade residential walls. This is offers a construction advantage. Note in some areas, local codes dictate that an 8" foundation is minimum width.

Improved Efficiency

ICFs provide continuous insulation for below grade foundation walls which exceeds code R-value and air-tightness requirements. Construction efficiency is achieved with ICFs because the insulation and finishes strapping are installed in one step along with the structural elements. This improved efficiency translates into lower energy bills for the homeowners with a comfortable and usable basement space.

Net-Zero Building

ICF construction is a key component in achieving net-zero designation for residential and commercial buildings. Insulated Concrete Forms (ICFs) are energy-efficient building materials that provide superior insulation, and that can reduce the amount of energy needed to heat and cool a building. ICFs also form an airtight construction, which minimizes air leakage and reduces the need for additional heating or cooling. With an increasing demand for sustainable building practices, ICF construction is becoming an increasingly popular choice for those seeking to achieve net-zero designation.

Use Fox Blocks to Create Foundation Walls That Can Stand Up to the Elements

Use Fox Blocks to Create Foundation Walls That Can Stand Up to the Elements

Building code foundation requirements are essential to ensure safe and durable structures, and Fox Blocks Insulated Concrete Forms (ICFs) offer you ease of construction, exceptional strength, a comfortable interior environment, and an eco-friendly method for building your next project.

We have decades of experience and thousands of satisfied customers, as well as a superior product design and knowledgeable customer service staff.

Contact us today to see how we can help you build better! We also have tremendous resources on the website for ICF training and contractor educational ICF courses and videos.