Pebbledash

A coarse, mottled, highly textured, riven form of render where aggregates are left at a larger fragment size rather than being ground down further and crushed to a more typical cement grain as is common in other renders and plasters. This particular roughcast contains a mixture of white and black stone fragments, with a light grey wash of natural lime – normally lime, chalk or other such softer stone types – colour. Roughcast differs from pebbledash whereby pebbledash applies the pebbles or stone fragments after applying the render, laying them into the primed and still curing surface by throwing them on with a particular type of trowel to ensure a random, even-spread coverage, whereas roughcast contains the pebbles mixed into the render putty. Like most renders, roughcast finishes are employed to protect masonry, adobe, concrete and other such wall structures from harsh, wet or marine climates, where resistance to corrosion of the base material from moisture, dirt and salt is imperative. Both roughcast and pebbledash finishes are preferred over cement renders in these cases as they are more malleable, stronger, less brittle and therefore less prone to cracking, breaking or falling off, while the lime content helps the wall ‘breath’, allowing moisture to escape so as not to damage the material it is covering, or the structural integrity of the building. Lime based renders cure due to a chemical reaction process when exposed to oxygen, rather than needing to dry out, meaning they are usually a more suitable option for cold, wet or damp climatic regions, and can be repaired in patches by applying fresh lime render which cures and sets with the existing wall finish, blending in more evenly. First used on common houses and outbuildings in coastal regions inhabited by working class people in the 17th century, modern roughcasting and pebbledashing were then widely used by developers on houses in suburban areas to respond contextually and to the prevailing climate of the regions in which they were constructed. Both roughcast and pebbledash finishes are however more synonymous with poor build quality in regions where these finishes were particularly common, such as northern Europe and America, as it was used by homeowners and builders after World Wars I and II when cost and material shortages were major concerns. Roughcast finishes required less manufacturing time than other renders due to the coarser grain of pebble fragments meaning less grinding and crushing time and effort, while it often helped hide poorly laid or cheap, stock masonry, providing a basic weatherproofing to potentially vulnerable, porous structures at a fraction of the cost of aesthetically pleasing, modern, robust construction materials. It had previously enjoyed popularity, being commonly used as a decorative finish on country manners, castles and estates, particularly in Scotland and Ireland, where vibrant colours and a huge variety in tone and texture can be obtained by utilising a multitude of different coloured pebbles.