Apply exterior plaster to polystyrene

A durable outer plaster can be applied to an insulating layer of styrofoam. Due to its specific properties, the insulating material, which is no longer up-to-date in new buildings, must be decoupled from the plaster. When renovating an existing building, it is possible to carry out an insulation replacement or a thermal protection application.

Exterior plaster and Styrofoam react differently to temperature influences

As an insulating material on the outer shell of the house and the facade attached Styrofoam plates can serve as a carrier for the exterior plaster of the house. Attention should be paid to the behavior of the plastic under fluctuating temperature influences. It differs from the exterior plaster and without decoupling the plaster does not last forever.

Several handicraft peculiarities must be considered when plastering:

  • The thickness of the exterior plaster must not be too thick
  • A supporting tissue filling provides sufficient stability
  • A decoupling layer allows the plaster to expand or contract independently of the polystyrene

Natural insulation boards can be plastered as well as Styrofoam

As an alternative to polystyrene panels, a thermal insulation can make sense of insulation on the outside. Alternatively, pressed insulation panels made of natural fibers are used. On them, as on polystyrene, an exterior plaster can be applied.

The central challenge, so that the plaster does not detach itself from the wall, is the harmonization of the physical properties of all materials involved.

Silicate-based thin plasters or mineral plasters are best suited for application to polystyrene. It must be noted that polystyrene "sweats" and a diffusing plaster allows the resulting moisture to escape again. A closed plaster without diffusivity can lead to "flushing" of the plaster layer, which sooner or later leads to detachment.

Tips & Tricks

Be sure to use plaster moldings on the edges of plastic windows and doors. The also available strips of metal quickly form thermal bridges and thus counteract the efficiency of the styrofoam exactly.

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Video Board: Traditional stucco systems VS styrofoam stucco systems