Superstructure (excluding roofs)

6

6.11Render

This chapter gives guidance on meeting the Technical Requirements for factory-made and traditional render applied to external walls, and render onto board backgrounds.

Render intended for below ground waterproofing is outside the scope of this chapter (see Chapter 5.4 ‘Waterproofing of basements and other below ground structures’). Chapter 6.9 ‘Curtain walling and cladding’ contains guidance for insulated render systems.

Introduction

This chapter is arranged in sections covering:

site and factory-made render

render onto board backgrounds

detailing.

Definitions for this chapter

Background	The surface to which the render is applied.
Base coat	The first render coat.
Cured	The finished render state when all chemical reactions have taken place.
Decorative finishes	An aesthetic finish not generally contributing to weathertightness.
Dry dash	Aggregate applied to finish the render.
Factory-made	Render mortar arriving on site premixed, generally including admixtures and colouring, and either ready to use or requiring only the addition of water.
Final coat	The last render coat.
Movement joint	A joint designed to accommodate predicted movement in the background or render.
Preparation coat	An application to provide an appropriate key or bond, including a spatterdash or stipple coat.
Proprietary render systems	Renders and their specified backgrounds with proven compatibility, which fall outside the guidance given for site and factory-made renders.
Ribbed metal lathing	Metal lathing that can be used as a carrier for render.
Site-made	Renders made on site to recognised designated or prescribed mix proportions.
Structure	Structural elements of the building providing support to the render or proprietary render system.
Substrate	The wall composition which offers support to the background intended to be rendered (the substrate and background may sometimes be the same).
Undercoat	The coats preceding the final coat.
Wet dash	A traditional render consisting of aggregate bound in slurry applied to the undercoat prior to setting.