The purposes of the walls in buildings are to support roofs, floors and ceilings; to enclose a space as part of the building envelope along with a roof to give buildings form; and to provide shelter and security. In addition, the wall may house various types of utilities such as electrical wiring or plumbing. Wall construction falls into two basic categories: framed walls or mass-walls. In framed walls the load is transferred to the foundation through posts, columns or studs. Framed walls most often have three or more separate components: the structural elements (such as 2×4 studs in a house wall), insulation, and finish elements or surfaces (such as drywall or panelling). Mass-walls are of a solid material including masonry, concrete including slipform stonemasonry, log building, cordwood construction, adobe, rammed earth, cob, earthbag construction, bottles, tin cans, straw-bale construction, and ice.