Building a home is not for the impatient or those fearful of decisions. It is a slow process with literally thousands of decisions, such as framing, foundations, siding, roofing, flooring, etc. One of the first decisions will be the type of foundation you want for your home.
The purpose of this article is to provide a very general knowledge (not technical) of basement foundations and give you a starting point in seeking the best choice for your home.
Types of Residential Foundations
There are three types of residential foundations: slab-on-grade, crawl space, and basement.
As we reside in “The Mountain State”, our home building site options are pretty much limited to slope and mountainous terrain.
The topography is well suited for walkout basement foundations which we did select for our custom-built home.
For the purpose of this post, we will limit our focus on basement foundations only.
A Basement’s Primary Enemy: WATER INTRUSION!!
Water intrusion is the unwanted presents of water, moisture, or water vapors.
Some experts estimate about 80% of foundation issues are ultimately linked to poor site drainage.
Depending on soil conditions, International Building Code (IBC 2015, Sec.1804.4) requires an average of 5% slope to move water away from the foundation.
We have clay soil here which expands when wet and then contracts as it dries. This constant movement of soil can wreak havoc on foundation walls.
We have battled the “water war” for years in our present home and more recently when we moved from our original house site due to underground water.
Moving water AWAY from your home is the most important measure you can take to protect your investment and keep your basement relatively dry.
Basement Foundation Choices
Basement foundation walls have three categories: block or masonry, poured concrete, and precast concrete.
All three types of foundation have advantages and disadvantages and are susceptible to cracks and moisture over time.
Please note most industry and government literature state some moisture and minor cracks in basement walls are inevitable.
The HUD publication Moisture Resistant Homes states in section 2.4.2, “… all concrete and masonry construction will develop cracks…”
Its going to happen, but we must make informed decisions, conduct maintenance to minimize those issues, and understand what is NOT normal.
Finally, it is possible to use an all-weather wood foundation. This was not a viable option for us, so if you are considering this type, make sure you do the proper research before starting your build.
1. Block Foundations.
Block or Concrete Masonry Unit (CMU) foundations are formed from concrete block rows placed on concrete footings, mortared together, then rebar and concrete are added to the cells to strengthen the structure.
The term “cinder block” is used interchangeably but there are differences in material, weight, and strength.
CMU foundations, despite being labor intensive, are usually the least expensive foundation (in our area).
Each mortared seam around a block is a potential problem area. The block itself is also porous and all block walls should be sealed.
If your basement will be used as living space, you need to also factor in the cost to insulate and frame these walls in addition to the cost of the block and labor.
For our build, the materials and labor for a block foundation were significantly higher than our other options.
This is generally not the rule and probably entirely situational to our area and the present cost of materials.
2. Poured Concrete Foundations
Poured concrete foundations are formed on-site using fabricated forms set atop concrete footings.
Insulated Concrete Forms (ICF) are an option, are not removed, and provide insulation on both the inside and outside of the wall.
Rebar is placed inside the forms to strengthen the wall. Concrete is then poured into the form creating a continuous foundation.
Poured concrete is an excellent foundation system and is most widely used by builders.
This foundation has no seams. It is a continuous concrete wall which means fewer places for water to invade.
The labor and time involved in building the forms on-site can make this system more costly. As with CMU foundations, you will also have to factor in the cost of insulation (unless using ICFs) and framing.
One major problem with poured concrete foundations is the possibility of a “cold seam”. This happens when the walls are not poured continuously to ensure good bonding and can cause this seam where the old section and new section of concrete join.
It is also important to note both CMU and poured concrete foundations are built in the elements and susceptible to weather conditions such as cold that can weaken concrete and mortar.
3. Precast Foundations
Precast foundations are sections of a foundation made in a controlled factory environment using metal forms, rigid insulation, and rebar for added strength.
Concrete is poured over a horizontal section and then the cured sections are transported to the build site. A crane is used to lift and place the sections, permanent joint compound is applied between sections, then they are bolted together and locked into place.
Most of these foundations are placed on a crushed stone footing, not concrete, which adds to the criticism of this type of foundation.
Benefits include a short installation time (one day in most cases), strongest concrete (5,000 PSI), green certified, as well as third-party certified due to manufacturing requirements.
This system is also drywall ready with studs and insulation included in the structure which saves money.
There are strict guidelines on site prep and post installation methods that must be followed to prevent voiding the warranty.
Problems to consider are site accessibility and possible problems with joint seals between sections.
Our Basement Foundation Choice
For our specific build, site, soil, and budget, we decided to use a precast system for our home foundation.
We chose Superior Walls by Collier Foundations Systems, Inc. located in Pennsylvania.
We were impressed by cost, ease of installation, the insulation R-value, and the system being drywall ready.
It is important to note, we have not received any compensation or discount from Superior Walls or any affiliate.
This article is based solely on our own experience and research.
For your convenience, we’ve created a foundation material comparison chart!
There is so much information on this subject, we didn’t begin to scratch the surface.
I researched countless company websites, expert blogs, professional associations, and government agencies for this article.
Surprisingly, some are deeply passionate about this subject and I did my best to remain neutral.
Ultimately, we are all influenced by our personal experiences and circumstances.
I recommend making your own informed decision based on your site and needs.
For additional reading and research, here are some helpful links to get you started.
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