Vertisols present unique engineering difficulties, due to their high linear extensibility. Special designs are necessary to avoid structural damage to buildings and roads. Structures can be built on slabs of concrete that float in the soil. Gravel placed around foundations may provide a buffer from shrink/swell. Pilings can be used to anchor a foundation on a more stable base. Other strategies include minimizing shrink/swell action by maintaining a relatively constant soil moisture content.