Lime cement plaster on gypsum plaster

Lime cement plaster is one of the most popular building materials. It can be used in many ways and when renovating all rooms are often plastered with it to ensure a homogeneous appearance. If gypsum plaster is to be covered with lime cement plaster, the craftsman faces problems.

Gypsum plaster does not provide a good base

The prerequisite for proper wall plastering is a substrate that is harder than the plaster to be applied. Gypsum plaster is much softer and lime-cement plaster is not an ideal substrate. If cement-lime plaster is nevertheless applied, the incompatibilities show up in the drying process. Lime cement plasters shrink when they dry. They are contracting. The resulting tensions between the different layers of plaster on the wall lead to flaking and cracks. The cement-lime plaster cannot stick to the gypsum plaster surface.

  • Also read - gypsum plaster or lime cement plaster for indoor use
  • Also read - gypsum plaster for the basement
  • Also read - felting gypsum plaster

Priming doesn't solve the problem

Spreading a primer such as Tiefengrund (4.81 € at Amazon *) on the gypsum plaster does not ensure the necessary adhesion. Primers are made on the basis of plastics and dry smoothly. Plaster does not adhere adequately to its smooth surface. If cement-lime plaster is nevertheless applied, it will come off in parts or completely. Other primers will not be firm enough to compensate for the tension between the layers of plaster. Here, too, the plaster tears and flakes off.

Lime cement plaster needs a lot of water

When mixing lime cement plaster, a lot of water is added to make the mass more pliable. This makes the plaster easier to work with. After the plaster has been applied, the water must evaporate in the drying phase. This is done, among other things, over the old plaster layer and the masonry below the lime cement plaster layer. Gypsum plaster is not resistant to this prolonged exposure to moisture. The cement-lime plaster cannot adhere sufficiently, the gypsum plaster is damaged by the moisture. Here the fresh plaster slips off its sub-surface.

Versatile design options for cement-lime plaster:

  • Processing of white or colored types of plaster
  • Structure with a lime spatula
  • Use decorative plaster
  • Apply tiles or wallpaper
Tips & Tricks Lime cement plaster can also be applied to smooth plaster surfaces with appropriate preparation. First of all, the substrate needs special processing. The smooth surfaces are provided with an adhesive filler. It is best to use a cement lime filler for the adhesive filler.