Soil testing is used in the agricultural sector to maintain the health of soils and provide a foundation for sustainable agriculture. In the building sector it is used to determine that the area is suitable for construction, and to select the proper type of foundation. Soil testing service providers can undertake a range of soil tests, such as particle size distribution tests, which determine the relative proportions of differing grain sizes within a soil and compaction tests, which determine the optimum moisture content to achieve a maximum density. Consolidation tests establish the settlement potential of fine grained soil, while direct shear tests measure the peak shear strengths of a soil. Constant and falling head permeability tests determine the hydraulic conductivity of coarse and fine grained soils.