Superstructure (excluding roofs)


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.


This chapter is arranged in sections covering:

  • site and factory-made render
  • render onto board backgrounds
  • detailing.

Definitions for this chapter

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