Steel stumps are by far the most popular stump choice. They are favored by engineers and builders alike for a number of reasons. Easy to work, readily available, strong durable and provided they are treated properly steel stumps are long lasting. In many cases the stumps are later enclosed within walls, with the help of support beams to remove some of the internal posts the area under the house is built in. In this case the stumps themselves disappear from site completely being enclosed within wall framing.
Steel stumps can be engineered and fitted to your house in different ways. The two more common place methods in discussion here differ mainly in the way they brace the building. If you were to compare them to something else structural like a car for instance. You could say one method is similar to a chassis with a body mounted to it. The other more like the modern car is a framework braced onto itself. As with everything efficiency in construction, cost of material etc has made way for new and better ways to support your building.
Stumping with bracing
The first method and more commonly used today for many reasons is a steel stump footed by a dense concrete footing. For a high set building the building is fitted with significant wind bracing between the stumps. This holds the understorey of the building from movement by bracing the posts onto each other in critical locations. This bracing is usually replaced when the building is built in. The walls are built and provide the necessary bracing in different ways.
Stumping with less bracing
The second method of choice is a deep reinforced footing or pier with the stump bolted between it and the building. This method uses significant materials as there is little or no bracing used. The piers or deep footing are generally 2- 3 times deeper and the stumps up to double in size. In both cases there is approx double the materials used. This method draws it strength from the deep piers and stump engineering to take the sideways force thus reducing the building overall bracing requirements.