The term ‘stucco’ is a technique used as a protective layer to the exterior of masonry or frame walls,. The stucco material is usually composed of cement, sand, hydrated lime and water and applied to the external layer while wet. Stucco has a wide range of applications, from being used as a stone imitation coarse plaster or cement for covering the rough exterior surface of walls to its use as a fine plaster (composed of the mineral gypsum and fine marble) for covering walls, ceilings and floors as well as for making cornices (a highly decorative horizontal ledge found on the top of buildings which functions as the building’s gutter, Fig.1), mouldings and other decorations.
Fig.1: An example of a cornice on the top of a building
In England, stucco comes in a variety of forms depending on its components, these being:
1) Common stucco - an exterior render prepared from hydraulic lime, sand and animal hair similar to traditional render
2) Rough stucco - a fine plaster made up of sand and lime (made from chalk, CaCO3) or a very pure limestone material (CaO).
3) Bastard stucco - usually composed of fat lime putty and fine washed sand but less time and effort is applied to making it. It is laid on the surface in two coats (approximately 3-4 mm thickness in total) by a technique called skimming using a float, scoured/ polished to remove any rough surfaces and is then trowelled.
4) Trowelled stucco - a fat lime render applied as a normal finishing coat, scoured/ polished and painted.