Topic 2. Interior Plasters

Characteristics of interior plasters

Interior plasters are finishing works on the construction or on a masonry course, which form the visible facing surface of the interior (wall, ceiling). Plastering is a wet process with manual or machine application.



Rough plasters

  • smoothe rough masonry surfaces
  • have antiseptic quality (lime plasters)
  • maintain temperature and moisture levels stable
  • are suitable for plaster bases, finishing painting and coating

Decorative plasters

  • have antiseptic quality
  • maintain temperature and moisture levels stable
  • provide better aesthetic view (colours, structure, ornamentation)


Plaster components – mortar, mixture of binder, filler and water, and/or additives and admixtures


1. Binder
a) inorganic binders:

  • air lime and hydraulic lime
  • gypsum
  • cement

b) organic binders:

  • synthetic resins
  • acrylic dispersions


2. Filler – the biggest part of the volume of the mortar;it is an inactive component (aggregate).
The type and size of the filler fractions is selected according to the type of plaster. No powder particles are allowed in the plaster composition. The content of clay particles must be below 2%.



  • crushed (quarry) sand
  • pit sand
  • river sand
  • manufactured sand (expanded clay, perlite, thermosite, agloprite)
  • organic substances (wood sawdust, crushed waste, granule polystyrene


3. Water – drinking water from the water supply network is suitable for the preparation of mortar. The water must be clear, free of harmful impurities, acids, salts, fats, etc. It must have a hydrogen index above 4 (pH>4).


4. Additives – used to modify the properties of the mortar.