Building Foundations Throughout History

The foundation of a building is an important link in the overall construction of a building. In each circumstance, the type of foundation best suited for a particular building depends on the final weight of the building, the type of soil the building will rest on, and the budgetary constraints of construction.
Types of Foundation Construction
Post in Grade and Post on Pier
The oldest foundations were built by digging holes and inserting posts into the ground to support the weight of the building. Another variation of this type of foundation construction consists of setting concrete piers on the ground surface and then setting wooden posts on top of the piers. The building is then constructed on beams resting on the posts. 
Modern building codes forbid direct contact of wood to soil, so posts set directly in the ground are a foundation type that is most often found in older buildings. Pier and post foundations were common in the early 20th century, but they are often inadequate because there is no solid foundation between the piers, resulting in a greater chance of soil to wood contact that can lead to termite infestation.
Continuous Concrete Footings
This is a common type of foundation found in modern buildings. A continuous beam of concrete is poured at the perimeter of the building. The footing extents below the surface grade to the frost line and above the soil for six to twelve inches or more. The building then rests on wooden plates set on this concrete beam.
Pier and Beam
In areas with unstable soils, it is common to drill piers of about one foot diameter down through the soil to the stable bedrock below. A continuos concrete footing is then poured between these piers. In this foundation style, the piers act like legs of a table, resting on the solid bedrock below. 
Slab on Grade 
This foundation type is made by first constructing a continuous pour concrete footing around the perimeter of the building and then pouring a slab of concrete inside this perimeter that serves as the floor for the lower level of the building. Slab on grade foundations require good compacting of the soil under the slab, vapor barriers, and a gravel base for good drainage under the slab.
Foundation Engineering
Using the services of a geo-technical engineer is an important step in construction of a building foundation that will be adequate for the weight bearing capacity of the building and the soil type. Much foundation repair throughout history is the result of not having an adequately engineered foundation when the building was originally constructed. An geo-technical engineer can determine the best foundation solution for preventing differential and total settlement of a building over time.