Void forms are sacrificial formwork members designed to provide a space between the concrete foundation and expansive soil, i.e., to protect the foundation from the heave of the underlying soil. They also offer a temporary support formwork for recently poured concrete till it achieves adequate strength to support its loads.
Moreover, void forms are utilized to decrease soil excavation and reduce the quantity of concrete. The depth of void forms under foundations ranges from 4” to 12” based on the underlying soil’s potential for upward movement. Where cases are greater than 6”, the void form is stacked to achieve the correct depth/height, or custom sizes are produced.
