How to Apply Plaster: All Types of Plaster for Interior and Exterior

Plaster is used to smooth the masonry before it is subsequently painted, wallpapered or tiled. However, some types of plaster look so pretty that further design becomes superfluous. But plaster can also perform other functions and, depending on the type of plaster, absorb and also release moisture, for example. What homeowners should look out for when having their house plastered – or taking on this work themselves.

The bare wall or wooden wall of a building is usually neither pretty to look at, nor is it well protected against moisture penetration. The plaster takes over these tasks at least partially. It smoothes the wall and prepares it for the application of paint or wallpaper – if it is not already decorative enough itself.

Exterior plaster: these types exist

Exterior plaster is always applied as a wet plaster. This means that the plaster dries on the wall first, because this is the only way to create a continuous protective shell. Since plaster consists of sand and various binders, it has different properties depending on its composition:

Synthetic resin plaster/dispersion plaster.

The binder is synthetic resin, from which the name is derived. Since dispersion refers to a mixture of at least two substances, this applies to any type of plaster. Synthetic resin plasters are characterized by great elasticity and resistance. They are highly water repellent, which is why water runs off the surface or evaporates – and is not absorbed by the wall. Therefore, the surface is susceptible to algae and fungal attack – at least unless antidotes are added to the plaster.

Mineral plaster

Mineral binders such as lime or sand give this plaster its name. The advantage of mineral plaster is that it is open to diffusion, i.e. it can absorb moisture from the air. It is also alkaline and therefore not a good breeding ground for mold or algae. The plaster is far less elastic than synthetic resin plaster and therefore less resistant.

Silicate plaster

It is not the binder but the silicates, which are usually bound with potassium water glass or synthetic resin, that give this plaster its name. The plaster combines the positive properties of synthetic resin and mineral plasters. It is thus more open to diffusion than synthetic resin plaster and at the same time more elastic than mineral plaster.

Silicone resin plaster

This is a synthetic resin plaster with silicone resin emulsion and polymer dispersions as binders. This plaster can be used on all substrates and is also elastic and open to diffusion. It also offers the best thermal insulation properties of all plasters.

Mosaic plaster/stained stone plaster

These plasters contain natural stone granules and are particularly resistant. This makes them suitable for use in areas subject to high stress, such as exterior basement walls and the base area of a house.

Inexpensive plasters, which still have to be mixed and are sold in bags, cost around 60 cents per kilo in DIY stores. Mosaic or colored stone plasters between one and two euros. Ready-mixed plasters can also cost three euros and more.

Interior plaster: the most important types

In contrast to exterior plaster, the requirements for interior plaster in terms of resistance are much lower.

Gypsum plaster

consists of gypsum and aggregates of different fine sizes. In this respect, gypsum plaster is a mineral plaster. It is open to diffusion and prevents mold growth, but should not be used in damp rooms and should not be painted over with emulsion paint, as this will destroy the good properties of the plaster. Lime paint is perfect for this purpose.

Lime plaster

is a mixture of lime and sand. This plaster is more expensive than gypsum plaster, but since it can regulate moisture, is antibacterial and prevents mold growth, it can also be used in the kitchen or bathroom. A special form, tadelakt, is also suitable for the wall in the shower or behind the bathtub. However, inexperienced do-it-yourselfers should not apply this type of plaster themselves, as the processing is very time-consuming and prone to errors.

Lime-cement plaster

Lime-cement plaster also consists of sand, binder, lime and cement. This plaster is relatively resistant to pressure as well as abrasion and is therefore also suitable for rooms subject to stress, for example, storage rooms in the basement. The plaster is also often used as a base coat for tiles in wet rooms.

Clay plaster

This ecological natural plaster made of clay and sand is one of the oldest building materials in the world. The plaster is easy to work with and has excellent moisture-regulating properties. However, because it is water-soluble, it is not suitable for wet areas of a home. Clay plaster is used primarily when plastering alternative building materials such as straw or jute.

Decorative plasters/structural plasters

All of the above plasters can become decorative or textured plasters through the use of paints or added minerals. Finishing the plaster while it is still wet can also turn a plain substrate into a nicely designed surface.

The alternative: dry plaster

At least indoors, there is an alternative to wet plaster: Plasterboard, also called dry plaster. These can be glued to unplastered walls or screwed on with the help of a support system. Processing is somewhat easier than wet plaster, but also more expensive. Inexperienced DIYers may leave visible transitions between the individual plasterboard panels.

Plastering a wall: How to do it

It is not easy to plaster a wall, because the plaster dries quickly and transitions that are not made wet in wet are visible later. Because the plaster is the basis of the later wall design, work here should be neat. However, some mistakes can be cleaned up after drying by sanding or wallpapering. Nevertheless, plastering is primarily about creating a smooth surface, which very few people succeed in doing right away.