Often, I got asked this question by the clients. Like many questions in building industry, there is no straight answer to it. As each of these two types of foundations has its own merit. However, there are two main factors when considering which one to choose: shape and slope of your land.
Generally flat land works better with concrete slabs while sloppy one works with stumps. As a builder, our company is passionate about sustainable building solution and thus is a big fan of waffle pod (polystyrene cubes) construction in conjunction of underfloor hydronic heating. However, this option is only good with relatively flat ground. Concrete slab on the ground also transfers latent heat from the earth into the building above. The temperature at 1 meter deep below the ground in Melbourne is constantly about 14 degrees Celsius all year round and this heat can be transferred into the building.
If the land is steep or very steep, then the best option is to build on stumps. Extremely steep land is sometime subject to potential landslide and additional precautions and engineering solution must be adopted to deal with this problem. Also there is need for additional underfloor insulation to reach 6 star requirements. The biggest benefit of building on stumps is great flexibility of construction and generally lower price in addition to much lower carbon footprint of your building. The depth of stumps is required to reach maybe as shallow as half meter or as long as 5 meters or even more in some extreme difficult terrain. Most houses were built on timber stumps in older days but not much in use these days. They can be made of concrete or galvanized steel.
If you are interested under floor hydronic heating, we can also install it in the house on stumps.