ABSTRACT
This chapter explains the development and use of modern external render. An external render consists of a wet-applied mortar/plaster consisting of a mix of binders and aggregates, that is trowelled onto the external walls of a house, often in a series of coats, forming a decorative and weatherproofing skin. The most obvious function for using external render is decorative. It can hide some poorer quality materials and construction, giving them far greater longevity than they would achieve if exposed to the elements. Modern self-mixed renders consist of binders and aggregates, applied in one, two or three coats. Smooth concrete and dense smooth bricks with flush joints do not provide a suitable background for render, unless some form of mechanical key is provided. One of the best methods is to use a stipple coat, comprising one part cement and two parts sand with a proprietary bonding agent, such as PVA.
