What are Foundation Walls? The Structural Element of a Building

Author: Brandon Johnson
January 25, 2023
Informational, Masonry

INTRODUCTION

In this article, we will discuss the different types of foundation walls and what they are used for, as well as provide a cost comparison of the different options. We will also explore the reasons why foundation walls are required and what the building code lists as requirements. Overall, this article aims to provide a comprehensive understanding of foundation walls and the role they play in the overall construction of a building.

SO, WHAT ARE FOUNDATION WALLS?

Foundation walls are the structural element of a building that transfers the load of the building to the ground. Foundation walls are required in order to provide a stable base for the structure. They are typically made of concrete, but can also be made of other materials such as brick, stone, or block. There are several different types of foundation walls, each with its own unique characteristics and uses. We will be discussing full-height walls, crawl space foundations, and slab-on-grade foundations in this article.

#1) FULL-HEIGHT WALLS

Full-height walls and when to use them

One type of foundation wall is a full-height wall, which extends from the footing to the top of the foundation. This type of wall is typically used for basements in residential construction, as it provides a large amount of storage space and can also be finished to create additional living space. Full-height walls are typically made of poured concrete and reinforced with steel rebar. The building code lists several requirements for full-height walls to ensure that they are able to safely transfer the load of the building and to meet structural and safety requirements.

FULL-HEIGHT CODE REQUIREMENTS

One requirement for full-height walls is that they must be made of a suitable material, such as poured concrete or concrete block. The building code also requires that the walls be reinforced with steel rebar to increase their strength and stability. Another requirement for full-height walls is that they must be designed to withstand the loads that will be placed on them, including the weight of the building, the weight of the soil, and any additional loads such as wind or snow. This typically requires that the walls be designed by a structural engineer.

FULL-HEIGHT WALL DESIGN

Full-height walls should be properly waterproofed to prevent water infiltration. This typically involves the using high compressive strength concrete and the use of a waterproofing membrane or a combination of drainage and waterproofing systems. Finally, full-height walls must be built to withstand the seismic forces that can be generated by an earthquake. This typically requires that the walls be designed to resist both the vertical and horizontal forces that can be generated by an earthquake.

#2) CRAWL SPACE FOUNDATION WALLS

WHAT IS A CRAWL SPACE?

Another type of foundation wall is a crawl space wall, which is a short wall that extends from the footing to the sill plate, where your traditional floor system sits on. This type of foundation is typically used in homes that are built on gently sloped or uneven ground, as it provides for the ability to properly direct stormwater and provides the space for mechanical systems such as HVAC and plumbing to be located under the floor system. Crawl space foundations are typically built with masonry units that sit atop of a concrete footing. Most residential crawl space foundations are built with CMU block (made of concrete) or a combination of block and brick.

WHEN TO CHOOSE A CRAWL SPACE

Crawl space foundations are typically best suited for home lots that have gentle slopes and soils that have a high load bearing capacity. They are not typically recommended for areas that have high water tables or are prone to flooding, as the crawl space may fill with water that can’t drain. Additionally, crawl space foundations are not recommended in areas that are prone to earthquakes or soil movement, as they may not provide enough stability to protect the home from damage. Crawl spaces are also not recommended for areas with high termite activity. In general, crawl spaces foundations are best suited for home lots in moderate climates with relatively stable soil conditions.

CRAWL SPACE CODE REQUIREMENTS

Building codes for crawl space foundations typically require that the crawl space be at least 18 inches from grade, be properly ventilated to prevent moisture buildup, and have a vapor barrier installed on the ground to prevent moisture from entering the crawl space. The specific requirements can vary greatly from region to region.

PROS AND CONS: CRAWL SPACE FOUNDATION

Pros:

Easy access to plumbing and mechanicals for maintenance / repairs.
Provides a buffer between the ground and the living space.
Can be less expensive than full basement or slab-on-grade foundations.
Can be combined with masonry veneer to create a nice aesthetic.

Cons:

Moisture and pest issues if not properly ventilated and sealed.
Limited headroom makes it difficult to store items here.
Can be difficult to properly insulate.
Limited protection from earthquakes and termites.

#3) SLAB-ON-GRADE FOUNDATION

AKA MONOLITHIC SLAB FOUNDATION

A third type of foundation wall is a monolithic concrete slab foundation (slab-on-grade) foundation, which is a slab of concrete that is poured directly on the ground. This type of foundation is typically used in areas with a high water table or where the soil is not suitable for a traditional foundation. Slab-on-grade foundations are typically made of poured concrete and reinforced with steel rebar. The slab and footing are poured at the same time, in one continuous pour.

WHEN & WHY TO USE A SLAB-ON-GRADE FOUNDATION

In general, a monolithic slab foundation can be a cost-effective option for a new home construction, but it may not be suitable for all types of building sites, climates, or soil conditions. Here in the southeastern U.S., developers buy a big chunk of land and make a master grading plan that will allow them to maximize the number of lots they can get from the parcel. This process allows them to setup the home lots to be relatively flat, so they can save money by using inexpensive concrete slab-on-grade foundations.

PROS AND CONS: SLAB-ON-GRADE FOUNDATIONS

Pros:

Provides a solid base to build on and cuts out the need for a floor system
Can be used in areas with a high water table or poor drainage.
Can be more energy efficient than other options
Saves money and time to build this way.

Cons:

Limited access to plumbing and mechanicals without demo.
Moisture and radon gas can be a concern and should be tested.
Not a suitable option for earthquake prone areas.
Not much protection from flooding due to it being on-grade.

IN CONCLUSION...

The article provides an overview of foundation walls, which are the structural element of a building that transfer the load of the building to the ground. The different types of foundation walls are discussed, including full-height walls, crawl space walls, and slab-on-grade foundations. Additionally, it explains why foundation walls are required and what the building code lists as requirements for full-height walls. The main goal of the article is to give a comprehensive understanding of foundation walls and the role they play in the overall construction of a building.

“It's not what you build a foundation with, it's how you build it that really matters."
Brandon R. Johnson

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Author: Brandon Johnson
January 25, 2023
Informational, Masonry

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