How to Choose the Right Foundation Types

 

foundation types

A Tella Firma system being lifted. See the whole video here: https://youtu.be/1H3ES7Yawf4

How to Choose the Right Foundation Types

Erika Oppenheimer, a renowned test prep coach, is quoted as saying, “Without a solid foundation, you’ll have trouble creating anything of value.” Although she relates this to creating maximum value when taking academic tests, it can be applied in the more literal sense when it comes to choosing the best foundation for an owner’s building or for your own home. In order to maximize the value of a building, the most critical initial step is to research foundation types and choose the most effective foundation for your building project.

From the Ground Up

According to the Soil Mechanics in Engineering Practice, a foundation is defined as the lower section of a building structure that transfers its gravity loads to the earth. This basic definition is then broadened when considering foundation selection criteria, which is dependent on two main factors:

  1. Ground/soil conditions
  2. Types of loads from the building structure

Ground/Soil Conditions

The Constructor – a civil engineering information resource site – recommends conducting a soil investigation for your project to find out:

  • Nature and type of soil
  • Depth of different layers of soil
  • Bearing capacity of the soil at varying levels
  • Level/slope of the ground

For example, when the soil close to the surface is not capable of supporting structural loads, hard strata (soil layer which has sufficient load bearing strength) must be found and most often results in the need for deeper foundations. In other cases, where there is uniform stable ground, a shallow foundation would suffice.

Load Types from Buildings

Loading conditions that affect selection of foundation types depend on the type of building for your project, locational/environmental factors and the type of structural construction materials used for your project. The Constructor cites factors that increase loads and necessitate deeper foundations, including:

  • High-rise/multi-story buildings
  • Exposure to strong winds or earthquake zones
  • Reinforced concrete buildings

Putting it all Together

Once soils have been investigated and loads types have been determined for the building project, now is the time to put it all together and select the best foundation type for the project. These main foundation types include:

  • Spread/wall footings

    • What it is: foundation type where the base is wider than a typical load bearing wall
    • Why it’s used: The wider base distributes the weight from the building structure over a greater surface area and provides more stability for the building
  • Drilled pier/deep foundation

    • What it is: type of deep foundation used to transfer heavy loads from the building structure to hard rock strata
    • Why it’s used: Can reduce the amount of ground disturbance, all while protecting against earthquakes and wind forces; also used where highly expansive near surface soils are present
  • Post-tensioned slab foundation

    • What it is: type of foundation that is spread across the entire area of the building to support loads from columns and walls
    • Why it’s used: Can be used on expansive soils

Best Foundation Types in Colorado Construction

According to the Colorado Geological Survey (CGS), expansive soils are a major issue faced by contractors in Colorado. CGS cites that clays cause more property damage than any other natural hazard. When exposed to water, they expand up to 20% by volume and exert up to 30,000 pounds of force per square foot, resulting in a contractor’s worst nightmare.

When selecting the best foundation type for buildings in Colorado, several factors must be considered. Post-tensioned foundations can be used to spread the structural building load over a wide area to help prevent damage caused by expansive soils. This type of foundation can be costly and can require over-excavation.

Drilled pier/deep foundations can be used on highly expansive soils; however, these typically require additional costs for structural floors at base mounts.

Another solution for highly expansive soils includes a foundation type recommended by RMG called Tella Firma. The Tella Firma process elevates the slab above ground, thus creating space that protects the slab and structure from the shrinking and swelling of our Colorado soils. The void between the ground and slab allows the soil to expand and contract as it absorbs moisture then dries.

Benefits of Tella Firma foundations include:

  • Multiple structure type uses, such as residential, multi-family or commercial projects
  • Environmentally friendly foundation with no chemicals used and no waste
  • More affordable option and takes less time to complete than most traditional suspended foundations

To create something of value, a solid foundation is required. When planning for your next building project, be sure to select the best foundation type that not only meets the soil conditions and load types, but also helps to save time and money on the project.

 

New Foundation System Appears to Levitate Above Harmful Expansive Soils

CONTACT:
John Clarke
jclarke@www.rmg-engineers.com
Phone: (719) 548-0600

Colorado Springs, CO – A groundbreaking new building foundation system is being introduced to Colorado. This innovative system provides solutions for expansive soil problems that are prevalent throughout our State.

RMG Engineers, a Colorado Springs-based architectural and engineering company, is the pioneer of the technique that is gaining fast recognition throughout the Front Range as a viable solution to a century’s old problem. RMG is excited to announce that the Tella Firma™ Foundations system is becoming the answer to most expansive soils problems. “Builders are constantly asking us for better ways to address our expansive soils problems,” says John Clarke, President, and Owner of RMG Engineers.

A new home is now being constructed by Vanguard Homes on this advanced new technique. The home will utilize the Tella Firma™ system in the basement and garage. This unconventional system, designed by RMG Engineers, lifts the foundation supporting the house off the ground from a grid of deep foundation piers, creating a more stable structure.

Expansive soil is defined as soil containing clay that swells when it is wet and often shrinks when it dries, creating havoc for many buildings foundations. When RMG conducts a soils test on a future home site, they may determine that the soil has certain expansive characteristics that could affect a traditional foundation system. The most common solution in the El Paso County area is to recommend an over-excavation scheme which involves the removal of three feet or more of the expansive soil and replacement with non-expansive soil. “The conventional approach of overdigging these sites is getting more expensive every year,” says Clarke. However, to avoid this costly over excavation option and promote a more stable foundation for the new home, Vanguard Homes has chosen to incorporate this innovative foundation design known as Tella Firma™. This patented system greatly reduces the potential for foundation and slab movement caused by expansive soil by literally suspending the foundation platform above the troublesome soils.

The patented process works by installing a grid of deep piers designed for the anticipated expansion in the soil. A structural concrete slab floor is poured on top of the ground and then raised six or more inches above the soils with the use of specially engineered lifting mechanisms supported on the piers; this creates the desired gap from the harmful effects of the expansive soil.

Constructing a structural floor above expansive clay soil has typically been considered the best approach to maintain a stable floor. Most structural floors require crawlspaces that are difficult to ventilate and involve deeper excavations and taller foundation walls. Using a concrete structural floor eliminates these requirements. But in the past, it had been costly to construct concrete structural floors which require elaborate form systems that were necessary to support the floor above the ground. This process was limited to more expensive homes and commercial buildings. Tella Firma™ Foundations system offers a unique and patented approach by lifting the concrete foundation without the use of the form system (as described above) at a more affordable cost, significantly reducing the required material, labor and construction time.

Tella Firma™ Foundations system also utilizes a post-tensioning structural concrete floor that is based upon existing engineering principals that have been in use for many years in commercial buildings and parking garages. Adapting a similar fundamental approach, RMG Engineers, has designed a stronger structural concrete floor that requires fewer support piers, further lowering the cost.

This current project is a residential home that will utilize the Tella Firma™ Foundations system for the basement and also the garage. While Tella Firma™ is not the only foundation system for a new home; it is the most cost effective in terms of protection from our volatile soils. “This system has already been used on the highly expansive soils in Texas in over 1000 homes,” adds Clarke.

Colorado Foundation Solutions (CFS) is the only supplier of the Tella Firma™ lifting mechanisms in Colorado. CFS also provides cost estimates to compare Tella Firma™ to traditional systems and training of, or references for, installation contractors. RMG, or your engineer, designs these foundations through our elaborate finite element analysis software systems.

CFS and RMG will be demonstrating the revolutionary process at the Vanguard Homes building site in a local Colorado Springs subdivision. RMG will be providing tours of the home site to all interested parties. Engineers, Architects, residential and commercial Builders, General Contractors, Land Developers and future home buyers are encouraged to tour the site and observe engineering innovation take place.

About RMG Engineers

RMG Engineers is a multi- service line architectural and engineering firm, headquartered in Colorado Springs, CO., with offices throughout the Rocky Mountain Front Range. The firm has been serving the Western States and Mid-West for 30 years. Staffed with a diverse team of licensed engineers and design professionals who are committed to delivering the highest level of quality in design, land planning, and engineering services. Project experience ranges in scale from residential to large commercial structures, land planning, geotechnical, forensics and providing an onsite lab for materials testing. Whether it’s a brand new design for a building, land development, a renovation, a remodel of a living space, or an addition to their home, RMG offers personal service and innovative design solutions through close collaboration with everyone involved.

About Tella Firma™ Foundations

Tella Firma™ Foundations is revolutionizing the way home foundations are built. Tella Firma translates “strong home” in Latin. The leadership team is leveraging a proven technology that was patented in 2011. Foundations with the Company’s product have been installed in Colorado and Texas.

Please contact RMG to schedule your tour or to learn more about the revolutionary Tella Firma™ Foundations system.

RMG Engineers
(719) 548-0600
tellafirma.com – rmg-engineers.com

Tight Infill Problem Solved with Tella Firma™ Foundation

Office and Apartment Building Under Construction

A property owner elected to construct an office and apartment building in a very small infill space in a historical Colorado Springs Neighborhood. Because the lot was located between two established businesses, there was very limited room for the use of heavy construction equipment. A new approach was needed that would eliminate the need to over excavate the bad soil and import structural fill.

The only realistic option was to construct a structurally suspended floor system, supported on a grid of piers. However, the construction methods used for “typical” structurally suspended floors still require at least 18″- 24″ of excavation.

As a result, the owner decided to use the Tella Firma™ foundation system because it requires virtually no excavation. With Tella Firma™, the slab is simply built on top of the existing ground and then raised, creating the necessary void between the soil and the foundation.

Tella Firma™ Example

Tella Firma™ is a patented process for constructing a new type of Structurally Suspended concrete foundation system. With this system, the slab is poured directly on top of the existing ground, after first installing a grid of piers or pads. In this case, helical piers were used.

After the concrete cures to the proper strength (typically 3 days), the post-tensioned cables are pulled, and the slab is raised to the desired height. This process utilizes mechanical screw jacks embedded in the slab, directly over each pier. Therefore, all the structural loads of the home are distributed to the piers which in turn distribute them to the stable soils below.

The slab is raised 6″ – 10″ above the ground, based on the recommendations of the Geotechnical engineer. The resultant void between the ground and the foundation serves to isolate the slab from any future soil movement. The problem soils may then move up or down in the future without affecting or even touching the floor.