We are Foundation Structural Engineers providing a vast array of Foundation Structural Engineering Services. Please visit our Structural Engineer San Antonio or our Structural Engineer Austin for for a list of some additional common engineering services that we provide.
Our Foundation structural Engineering services most commonly include:
Below is in article written by our staff to better explain some basics of foundation engineering. Enjoy! And please, ask us questions if you have any.
Foundation Engineering is in fact not a profession in itself, rather it is just part of the many types of services provided by a Structural Engineer because it involves the design of just one structural engineering system in the entire structure. There are, however, specialized Structural Engineers who do nothing but foundation repairs or even inspections or investigations of foundations problems, and these are usually referred by the general public as Foundation Engineers. While a Structural Engineer is also a Foundation Engineer, a Foundation Engineer may not necessarily be licensed to practice structural engineering.
To design a foundation, a structural foundation engineer also usually requires the soil data and recommendations from a geotechnical engineer. Therefore, in a sense, foundation engineering includes the cooperation of structural engineers and geotechnical engineers. The Foundation Engineer designs the footings, slab, beams, etc. based on the soil recommendations given by the geotechnical engineer. Though the services of a geotechnical Engineer are preferred, they are not require by code (International Residential Code and the International Building Code).
The foundation engineer must be careful in designing the foundation for the given type of soil. The foundation engineer takes several things into consideration when designing the foundation, the most important things to consider are the type of soil, the type of loading, the type of building or house, the expected performance and use of the building or house.
The design methodology to be used to engineer a foundation is given by the International residential code and the international building code. The codes don’t tell you how to design a foundation; they just point to what acceptable books and references to use to engineer the design of a foundation.
There are 3 general points of information you must gather to design a foundation:
The first thing needed to start the foundation engineering is the soil engineering data. The soil engineering data is usually provided by the geotechnical engineer; however, if a geotechnical engineer is not hired, then the soil engineering properties can be somewhat conservatively be assumed by the foundation engineer with the help of the international building code or the international residential code. The geotechnical engineering report advantage is that the actual soil below the house or building is known and the soil engineering capacities are better than the ones assumed and given by the code.
The soil Engineering data includes the soil load bearing capacity, as well as the behavior of the soil (is it expansive, compressive, or stable soils). Each type of soil has different engineering properties and each town, and even neighborhoods, have different types of soils. A foundation Engineer also must realize that the soil type may change as you go deeper from the surface of the soil
For example, in San Antonio, Texas, you will find a very expansive type of clay, commonly called, “fat clay”, everywhere in town. However, in some types of town (usually north of 1604) when you dig a few feet you will bump into solid rock (limestone). When water gets into these clays, then the soil tends to expand and if the foundation was not engineered correctly then a lot of damage can occur to the rest of the structure.
A weak type of soil, such as clay, not only can expand or contract easily with addition of water, but it also has a very low load bearing capacity. A strong type of soil such as Rock (Limestone) on the other hand, is very stable (i.e. will not expand and contract with the addition of water) and it will give you a much higher load bearing capacity.
Interestingly enough, most commercial or house foundation problems are related to a foundation that was not engineered correctly to account for the expansiveness or compressibility of the soil.
The foundation engineer, i.e. the structural engineer, must calculate the correct loads imposed on the foundation. For commercial work, the loads on the foundation can vary greatly depending on the type of building. For residential work the type of foundation would not be changed dramatically (unless you’re building an apartment complex, or condos, etc.). For a house, the load usually taken by the foundation will not substantially change the size of a foundation beam. The typical loads for a house usually consist of the self weight of the house (floors, roof, tiles, beams, brick walls, etc) as well as at least a code minimum live load of 40 pounds per square foot (psf) for livable space as well as 20 psf for the roof. Secondary loads that may affect the foundation are wind loads, seismic loads, flooding, wave action, etc.
For example, if you want a good start to determine the width of a foundation beam along the perimeter of a house foundation, a Foundation Engineer in San Antonio (i.e a structural Engineer) would start with measuring the height of the wall to determine the weight of brick on the wall -brick weighs about 50 psf, and a wood wall weighs about 10 psf, so if you have a two-story house, say 20 ft of height of wall, then the load on the perimeter foundation beam is 20ft x 60 psf = 1,200 pounds per foot (lbs/ft). If the closest load bearing wall from the perimeter wall of the house is, say 25ft away, then you would take the self weight of the roof (about 20 psf for a typical house with shingles) and the self weigh of the floor (about 30 psf for a typical house floor with carpet), as well as the live loads to the roof (20 psf) and the typical floor (40 psf) and multiply it for the portion of the wall that is taking that load. For a perimeter exterior wall on the house, in this case the foundation engineer would calculate the additional load on the foundation from the floor and the roof of the house as being (20 + 30 + 20 + 40) x 25/2 = 1375 lbs/ft. So, for this example, the total load on the foundation exterior beam would be 1200 + 1375 = 2575 lbs/ft.
In San Antonio and Austin, Texas, the allowable soil bearing capacity for clay would be anything between 1500 psf and 2000 psf. If you’re in an area in San Antonio where you can use the 2000 psf bearing capacity, then 2575/2000 = 1.29 ft wide beam (16” wide beam). This is just an example using gravity loads and a typical standard condition – do not use this to design your house or building!
The above example only took into consideration the gravity loads. A foundation engineer would also need to consider the forces created by the heaving or settling of the soil against the foundation, the horizontal forces due to wind, earth quakes, etc. So, for a foundation as described in the example above, the foundation beams may be wider and deeper.
Many people when requesting a foundation design for residential projects to a foundation or structural engineer, such as for houses, make a point to tell the foundation or structural engineer that they don’t want a commercial design. There are two problems with this kind of request: first, concrete and soil in the foundation don’t know if you’re putting a house or a 10 story building... and second, the residential code as well as the building code have the same requirements to design a foundation.
So foundation engineering is not based on whether it’s a commercial or residential foundation but rather on the type building being supported and their expected performance over time.
For example, a Warehouse is expected to have walls and doors around the perimeter that don’t move, but the interior slab of the warehouse is seen as a wearing surface that is expected to carry heavy forklift loads. A house can also have different criteria; for example, if the owner of the house accepts the foundation to move and cracks to occur in the walls, then the engineer will design it according to the minimum standards of the building code. However, if the home owner doesn’t has a more stringent expectation, then the soil would be removed all the way to the rock and if not possible then the foundation would be completely suspended from the ground with piers.
In structural Engineering (foundation engineering) there are 4 types of concrete foundations, simply Type I, Type II, Type III, and Type IV, according to the Building Research Advisory Board (BRAB). In short, Type I are non structural foundations, such as side walks, Type II are foundations without interior stiffening beams, Type III are foundations with interior stiffening beams, and type IV are suspended foundations, which are pier supported foundations (which are not necessarily all concrete). All these foundations types, except for Type IV, are foundations known as slab on grade foundations.
As we previously mentioned, the type of foundation for a building has to do with the type of soil as well as the type of use for the house of building.
Generally, if a slab foundation is on stable soil, such as rock (or even the sand), then a Type II concrete slab foundation is acceptable; the foundation would consist of a perimeter beam around the house or building.
If the foundation is on expansive soils, then the foundation engineer would need decide or consult with the owner about the kind of performance expected in the building. The code says that for expansive soils, such as the ones encounter is virtually all of San Antonio, Texas, you must use either a Type III or a Type IV slab.
When using a Type III foundation, the slab foundation would consist of a grid of concrete grade beams across the slab Engineered to minimize the amount of vertical movement. The spacing of the beams varies; the worst the soil the closer the spacing of the beams. According to the code, the spacing of the beams must not exceed 15ft on center. It’s important to realize that the foundation is engineered to minimize the movement of the concrete slab, but not eliminate it. If the homeowner is not willing to accept any cracking in the walls then a Type III foundation may not be acceptable and a Type IV foundation may be the only solution.
A type IV foundation is substantially more expensive than the Type III foundation if the entire foundation is made out of concrete. A type IV foundation is a pier foundation, where the piers could be made out of concrete, steel, or even wood. A foundation engineered to support a concrete floor can only be supported by concrete piers or steel piers (steel piles or helical piles), whereas a foundation engineered to support a wood floor can be supported by any type of pier foundation.
The design of the piers themselves is relatively easy in comparison to the design of a Type III, stiffened beam, Foundation. To prevent movement of the pier foundation, a foundation engineer must ensure that the piers are deep enough so that the soil moisture variation doesn’t affect the movement of the piers. In San Antonio, Texas, for example, piers must be deeper than a depth of approximately 15ft (the actual depth is properly determined by the geotechnical engineer). So, if a house or a building has a pier foundation where the depth of the piers is less than 15 ft deep, then the pier foundation would not serve its intended purpose and in fact will behave much worse than a stiffened type III concrete foundation.
There are also basement types of foundations, where the beams and footings are designed as cantilever or pinned retaining walls. In this case, the beams are in fact concrete walls, and the footings supporting the retaining walls also support the weight of the structure.
When a foundation is properly engineered by a structural engineer the chances of having foundation problems are minimal. Something that could affect the performance of the foundation is the construction as well as the type of service given to the house or building. In a house or building, it’s important for trees to stay as far as way possible from the foundation as well as having good drainage around the house or building in order to drain water away from the structure. Since soils are affected by the amount of water infiltrating into them, then avoiding anything that could change the amount Retaining Walls of water or moisture below the house or building is key to avoiding foundation problems.
By simply providing a positive slope of the ground to drain water away from the house or even providing a sidewalk or parking right adjacent to the structure could prevent water infiltration into the soils below the foundation and hence prevent potential foundation problems with the building.
Most people believe they have a foundation problem when in fact they don’t. Our Structural Engineering staff has written some good articles fully explaining some of the most common misconceptions about foundation problems. Some of these articles can be found
When you do have foundation problems, then the question always is whether the cracks in the walls, ceiling, etc. bother you. In general, when you do have a foundation problem the foundation engineer will ask you whether you can live with the problems because as a competent structural engineer he will know that most foundation problems will not cause failure in the slab.
Therefore, repairing a foundation is most of the times a question of aesthetics. If you think the cracks are not “pretty” then you need to ask yourself whether it is worth to you spending $25,000 on a foundation repair that will only accomplish partially improving the foundation (we say partially because most repair foundation companies will only repair the perimeter of your house or building, and not the interior) and reducing (but not eliminating) the amount of potential cracks in the future.
We will save more specifics about residential foundation repair engineering for another article, but the most important thing to point out is that foundation repair companies are extremely biased when telling you whether you have a foundation problem or not, and more often than not (please believe us, we speak on experience) the foundation repair company will claim you have foundation problems when in fact you do not. It’s not worth spending $25.000 to repair a problem you don’t have! The safest and cheapest thing to do is hire an independent structural engineer who will not benefit from doing a foundation repair, such as A-1 Engineering if you live in pr work in to San Antonio and Austin Texas.
And by the way, a foundation repair would still not repair the cracks. The owner would still need to hire a different person to do the actual repairs for cracked walls, ceilings, etc.
A good foundation in San Antonio and Austin starts with a good foundation engineer who is a structural engineer and has substantial experience in the design of commercial and residential foundations in San Antonio and Austin.
Unfortunately, money talks, and when it comes to building a residential house foundation, the contractor will almost always try to cut corners when hiring a structural engineer to design the foundation and when constructing the slab.
If you’re a future homeowner looking to build a house, whether a custom home or a regular home, you should request structural engineering plans showing the foundation. Better yet would be for you to have a choice on what structural engineer to use to design the house foundation.
If a foundation engineer works directly for the homeowner then the foundation engineer will know what type of foundation to design and will also check the construction of the foundation for general conformance with the structural foundation plans. Hiring a structural engineer to perform foundation engineering on your house or building is a lot cheaper than you think (for a quick reference check out our rates).
It’s important to hire a foundation engineer in San Antonio or Austin or an engineer who has extensive experience in the design of foundations in San Antonio or Austin. When it comes to foundation design in San Antonio, one must ask whether structural engineering company or the structural engineer in charge of your foundation design is familiar with the design of commercial foundations, in fact, give them a test, ask them what different types of foundations there are according to the code (International Building or Residential code), they should answer type I, II, III, and IV, if they don’t know then they very likely don’t know about foundation design… You will soon learn that some engineers in town that design residential foundations are “pirates” and not really structural engineers, especially here in San Antonio, Texas, and their foundation engineering is just an uneducated guess.And for more on where do you need a Structural Engineer in San Antonio or Austin, just click Structural Engineer San Antonio Structural Engineer Austin
We hope this article was very helpful to you, and if you have any more questions or need help on your next project in San Antonio or across Texas, please do not hesitate to