Traditionally, English cob was made by mixing the clay-based subsoil with sand, straw and water using oxen to trample it. English soils contain varying amounts of chalk, and cob made with significant amounts of chalk are called "chalk cob" or "wychert". The earthen mixture was then ladled onto a stone foundation in courses and trodden onto the wall by workers in a process known as "cobbing". The construction would progress according to the time required for the prior course to dry. After drying, the walls would be trimmed and the next course built, with lintels for later openings such as doors and windows being placed as the wall takes shape.