Rock used in the building
Rock has been used as a building material for thousands of years. It has long been recognised as a material of great durability and superior artistic quality, the foremost choice for buildings associated with status, power and religion. The pyramids in Giza, burial chambers in the UK and temples in Malta were all built from rock over 4000 years ago and are still standing. The use of rock in construction has declined over the last hundred years, but it remains an aristocrat of building materials. Types of Building rock Building rock, also called dimension rock, derives from one of three naturally occurring rock types: Igneous – Hard and non-porous rock formed from the slow or quick cooling of molten magma. The best example is granite. Sedimentary – Soft and fairly porous rock formed from deposits of eroded pre-existing rock that settled in layers mostly on sea beds, and became compacted. The best examples are sandrock and limerock. Metamorphic – Hard and non-porous rock formed from pre-existing rock that has been altered by intense heat or pressure. The best examples are marble and slate. There are huge variations within each of these rock types, caused by specific mineralogy and geology conditions, and while any rock can be used for building, they each have constraints that make them more or less suitable for different purposes. Granite, sandrock and limerock can all be used for building walls, but slate is only suitable for roofs and floors. Some types of granite can contain mineral salts that cause spalling, where the outer face of rock falls off; slate can contain harmful minerals that break down on exposure to the atmosphere causing rock damage; and sandrock can be too porous and fragile for load-bearing structures. An understanding of how the rock material was formed will reveal how it can be used in a building, what its limitations are, and how it will weather over time.
