Interior plastering guide: types, structure and cost

Interior plastering guide: types, structure and cost

The interior plaster is the basis for numerous works in the interior, ranging from the use as a coating base to the decorative structure. The interior plaster is mainly used to make the interior habitable. The numerous species have an insulating, moisture-regulating effect and protect against mechanical and chemical loads. The types, structure, and cost are important when applying interior plaster.

When building houses, renovating interiors, or building a new basement, interior plasters are among the most important coatings. They work effectively against the effects of the weather, moisture, noise and, depending on the type, can have a decorative function. Applying plaster indoors requires good planning to apply the right type. Likewise, without sufficient information, there can quickly be a material shortage or excess, which can drive up costs accordingly and bring the workflow to a standstill. This is why an interior plastering guide is important when you need plastering for a project. This, in addition to the types and structure, extensive cost examples are presented.

Construction of interior plaster

The basis for an effective interior plaster is the structure. Only with a correct construction is it possible to use the plaster over a longer period without any defects or other nasty surprises. While the different types of interior plaster determine the quality and further processing options, the correct structure allows it to be used in the first place. Several layers are used in the construction, which is applied to the wall or ceiling at different heights. These are named:

  • Concealed
  • Finishing coat

As the names suggest, these are layers that are applied to one another. The top and bottom plaster turn the interior into a weather-resistant and insulating layer that hides the adjacent wall. The plaster is not visible and is applied with a thickness of one to ten centimeters, depending on the project. The layer thickness depends heavily on what kind of wall it is. For an external wall, for example, a thicker concealed plaster is more recommended than for a room that is directly adjacent to a stairwell. On average, concealed layers of one to three centimeters are used in residential buildings. It is important that this is applied professionally and completely, otherwise, the following problems threaten:

  • Flaking
  • Formation of cracks
  • bad insulation
  • poor opacity
  • Finishing plaster cannot be applied properly

Since the finishing plaster is not that thick, it is usually much less needed. The typical layer thickness for the finishing render is 0.3 centimeters to one centimeter. The total thickness of the interior plaster is specified in the following standards:

  • DIN 18550-2
  • DIN EN 998-1

Since the interiors are not so heavily used rooms, the plaster is kept thin. In this case, the plaster thicknesses between 0.3 centimeters (thinly applied finishing plaster) and two centimeters (complete plaster system) are sufficient, which corresponds to the standards. A thicker plaster of at least two centimeters is only required for basic renovations, as the concealed plaster is often completely removed in this case. The thickness of the layer is important because it saves you excess costs that can often arise with plaster systems. As already mentioned above, the top coat is applied to the base coat. The concealed installation also has the following properties:

  • fills bumps such as small holes or cracks
  • enables an even surface for the finishing plaster
  • The top coat adheres better to the base coat

The finishing plaster, on the other hand, serves as a usable plaster layer inside, which can be smooth or structured. It enables wallpapering and painting, as the top coat has a different texture than the bottom coat. Here is the biggest difference between the two layers. Plastering must create a tension compensation. Due to climatic causes in the wall, it can expand and contract, which requires an elastic plaster. For this reason, the concealed plaster is softer and more elastic than the finishing plaster. While the concealed plaster balances out the tensions and insulates the interior, the solid plaster protects the concealed plaster. This is where the materials used come into play, which at the same time determine the types of interior plaster. The top and bottom plaster are not mixed from the same materials. More on this below. Interior plaster can be applied in the following ways:

  • Finishing and concealing
  • only flush-mounted
  • exclusively finishing plaster

The reason for this is the various possible uses. If, for example, a room is plastered that is not on an outside wall, a finishing plaster can be sufficient without any problems. If you are not sure about the desired structure, you should contact a specialist. They can assess the situation and provide you with more detailed information about the appropriate structure. For example, you need a different structure for a new build than for a house in need of renovation that has old masonry. The type of room must also be observed, as damp rooms, for example, require other systems.

Tip: If you want to apply decorative plaster to an already plastered wall, you have to remove the finishing plaster beforehand, otherwise it would be difficult to hold. Decorative plaster is a special layer in the structure that is only applied thinly to implement creative accents or designs.

Note the subsurface

If interior plasters are used, the substrate must be prepared beforehand. A wide variety of masonry with different properties awaits inside. These include:

  • brick
  • Concrete or aerated concrete
  • Ytong
  • Sand-lime brick
  • OSB panels
  • Plasterboard

All of these fabrics can be plastered, only certain preparations have to be made. If you just want to apply the plaster like that, the mixture will either be sucked up by the wall or “burned on”. This leads to a bad result, which affects the function of the plaster. It is also a typical problem that the plaster does not adhere because the masonry is too smooth. For this reason, you have to use a so-called burn-on barrier with porous or highly absorbent materials. On the other hand, if the surface is too smooth, adhesive bridges are necessary. The plaster can then be applied to this. If you are not sure about the condition of the masonry, also contact a professional. That makes planning a lot easier.

Interior plaster: types

One of the most important steps in implementing the interior plastering system is choosing the type. Interior plaster is offered in several different materials that determine the properties of the plaster system. As explained above, different types are used for the concealed and upper plaster, which complement each other. You should never use one type of plaster for both layers, otherwise, instability will result, which will harm either the masonry or the interior. The following sections introduce you to the typical types of interior plaster. The costs for the square meter relate to a layer thickness of ten millimeters.

Gypsum plaster

Gypsum plaster is the classic finishing plaster that is used for interiors. Walls and ceilings can be coated with high-quality interior plaster. Gypsum plaster can be used decoratively, acts as effective fire protection, and even releases moisture in the event of a fire. The species regulates moisture excellently, is breathable, and thus creates a good indoor climate. It should not be used in damp rooms. Gypsum plaster is often used due to its unproblematic processing and is a structurally and ecologically harmless variant.

Costs: 0.40 – 1.50 euros per m²

Gypsum-lime plaster

Gypsum-lime plaster combines the properties of gypsum and lime and is used as a base coat. It can be applied to the following masonry:

  • Brick
  • Sand-lime brick
  • Natural stone
  • concrete
  • Aerated concrete

It is also harmless and excellently balances out the tension in the wall. The effective vapor diffusion and climate regulating properties are ideal for interiors. In addition to a finishing plaster, it can also be combined well with filler.

Costs: 1 to 2 euros per m²

Lime plaster

Lime plasters reduce the formation of mold due to their alkalinity and excess moisture in the air is effectively removed from the room. The mineral finishing plaster can be smooth or coarse and is therefore often used decoratively. In terms of cost, a high-quality level can be extremely costly. They ensure an extremely pleasant room climate and are easily diffusible. Depending on the type, lime plasters are even shock-resistant if they are modern products. Otherwise, they are designed for light to moderate use.

Costs: 0.6 to 30 euros per m² (heavily dependent on the quality level)

Tip: Tadelakt from Morocco is a special form of lime plaster, which is a water-repellent and high-gloss plaster that is suitable for particularly high-quality damp rooms. Tadelakt is one of the most expensive interior plaster systems with a square meter price of easily 100 euros, as it is very difficult to apply, which requires a specialist.

Lime-cement plaster

A base and topcoat based on lime and cement, which has waterproof properties indoors. It is one of the classic types of damp-proof plaster that has a great effect even when applied thinly. The robust properties are ideal for a concealed installation, especially if the masonry is cold or drafty. At the same time, too much moisture is absorbed well. Even heavier loads can be withstood without any problems.

Costs: around 4.5 euros per m²

Thermal insulation plaster

The thermal insulation plaster is ideal when the masonry in the interior is particularly cold. They are either flame-retardant or non-combustible (DIN 4102) and are provided with numerous additives that support this property. The flush-mounted variant can mainly be used for masonry that does not comply with the EnEV (Energy Saving Ordinance). The following possible uses are to be mentioned:

  • Passive houses
  • Low energy houses
  • Attics
  • energetic renovation
  • thermal renovation
  • Improvement of the general insulation properties

They are easily stretchable, elastic, resistant to tears and movements, and completely water-repellent.

Costs: 4.5 to 6 euros per m²

Synthetic resin plaster

One of the most expensive variants is synthetic resin plaster, which is not made from mineral substances. These are dispersion plasters that are obtained from polymer dispersions and mixed with the following additives:

  • Silicone resin emulsion
  • Potash water glass
  • Resins (dissolved)

They look like conventional plaster but are used exclusively for finishing and decorative plasters. Ready-mixed, they are available in numerous colors and structures, which is what makes them so expensive. They adhere well to mineral plaster, have extremely high resistance, and are even impact-resistant. ETICS (thermal insulation composite systems) and bridging cracks are also possible through the use of synthetic resin plasters.

Costs: from 20 euros per m²

Clay plaster

According to its name, clay plaster is mixed with clay and a large number of other additives:

  • fine earth
  • sand
  • Clay powder
  • Marble sand
  • Plant starch
  • cellulose
  • Color pigments
  • Vegetable fibers

In addition, they are provided with a variety of so-called effect substances that provide colors or grains. As a finishing coat, it is very difficult to work with, but it looks elegant and appealing. They look very natural and have good properties for any interior. Clay plaster does not burn, is diffusion-open, soundproof, and effectively insulating. Humidity is regulated and even fine dust and allergens are filtered out of the air. It is precisely these properties that make the plaster so popular. These are just as suitable for old buildings. When building clay plaster, it is important to use professional edge protection, as it is a water-soluble type.

You can check more content in our category ” indoor “

Costs: 6 to 40 euros per m² (heavily dependent on quality and design)

Costs for interior plaster renovation

Of course, in addition to the structure and types, the costs of interior plastering should not be disregarded. Since interior plaster systems are applied wet, too much material can quickly be ordered, which has a negative impact on your budget. The individual cost points for the project must therefore be calculated precisely in order to limit losses. The following points arise when calculating the interior plaster system:

  • Material for the interior plastering system
  • Size of the wall or ceiling
  • quality
  • The texture of the walls
  • The new or old building
  • Working time and effort

Do not be surprised if your desired cleaning system causes significantly higher costs than you imagined. This is due to the individual positions, which can be very different. An average of 8 euros per square meter to 50 euros per square meter is assumed, whereby the quality level can increase the prices. There are the following quality levels that are suitable for different applications:

  • Q1: highest quality, paintable, smooth surface
  • Q2: well suited for painting, light-weight wallpapers can be used
  • Q3: normal wallpapers can be used, matt surface
  • Q4: rougher, suitable for tiles

Quality levels Q2 to Q4 are used in most private homes. Only finishing plasters are designated with this quality level, as the base plaster does not have the same function. If you want a Q1 plaster, you have to reckon with around 150 to 300 percent higher costs for the finishing plaster. With the other quality levels, the price difference is limited. You can assume about 15 to 50 percent of these. The price increase is caused by the high effort because the companies have to invest significantly more time and work in the project (depending on the quality level). The cost differences between new and old buildings, on the other hand, are to be considered as follows:

  • Old building with flush mounting: 8 to 15 euros per square meter
  • New or old buildings without concealed installation: 20 to 50 euros per square meter

This information is based on empirical values, as each company has slightly different costs. The prices for the interior plaster are usually given in euros per square meter. Since the layer thickness in the interior is not as thick as for the exterior plaster, square meters are completely sufficient for the determination. In order to calculate the square meters of the area to be plastered, you now need the following measurements:

  • Length of the wall or ceiling in m
  • Height of the wall or width of the ceiling in m

These values ​​are inserted into the following formula

(Length of the wall or ceiling in m) x (height of the wall or width of the ceiling m) = area to be plastered in m²

The areas of the individual walls and ceilings are then added together. Areas of windows, doors, and other openings are also calculated and deducted from the total. Since these are not plastered, you do not have to get any additional material and the working time is reduced accordingly. Based on the area to be plastered, the quality level, the type, and the workload, the necessary costs can be determined quite well.

Sample calculation

To give you an overview of the costs, the following is an example of a room with 40 square meters of wall area to be plastered. A plaster-lime base plaster and plaster top plaster were chosen, which are among the inexpensive interior plaster variants. The following is the cost example:

  • Concealed: 700 to 750 euros
  • Finishing plaster: 350 to 400 euros
  • Ground coverage: 180 to 200 euros
  • Total costs: 1,230 to 1,350 euros
  • Costs per m²: 30.75 to 33.75 euros

These prices already include the costs for the operation, for example, salaries and travel. Likewise the preparation of the subsurface. Since gypsum plasters require little effort, the costs are kept low in this case. You can create the invoice yourself based on the material costs and the costs for the operation. Therefore, find out in advance about hourly rates, salaries, or flat rates in order to determine the approximate price yourself by offsetting this with the material costs. The price increases depending on the individual types of plaster can be recognized from the material costs alone, as listed above. If you would like a Q1 interior plaster as an example, the costs could be as follows:

  • Concealed: 700 to 750 euros
  • Finishing plaster: 1,000 to 1,250 euros
  • Ground coverage: 180 to 200 euros
  • Total costs: 1,880 to 2,200 euros
  • Costs per m²: 47 to 55 euros

As you can see, a high-quality finishing plaster is almost twice as expensive. If a more expensive concealed installation is chosen for this, plastering can lead to enormous costs even in small rooms. When renewing the topcoat, on the other hand, you pay significantly less because the old one is removed and replaced. This could look like this if the walls are wallpapered and a Q3 finishing plaster :

  • Finishing plaster: 350 to 400 euros
  • Remove wallpaper: 250 to 300 euros
  • Ground coverage: 180 to 200 euros
  • Total costs: 780 to 900 euros
  • Costs per m²: 19.5 to 21 euros

The cost of plastering a ceiling is calculated in the same way. For a room with 40 square meters of wall surface and 20 square meters of the ceiling, these are offset against the total costs. However, the bill does not increase the cost of the floor cover, as this always remains the same. The last example deals with plastering the walls and ceiling with interior plaster :

  • Concealed: 1,050 to 1,125 euros
  • Finishing plaster: 1,500 to 1,875 euros
  • Ground coverage: 180 to 200 euros
  • Total costs: 2,730 to 3,200 euros
  • Costs per m²: 45.5 to 53.5 euros

Correct planning, including recording the type of wall and the necessary primers for the plaster, is important when drawing up costs. For a new building, the cost of the entire interior plaster is around three percent. The costs vary greatly from region to region and from company to company. For this reason, comparisons are essential before you order the interior plaster.

Is personal contribution possible?

At this point one of the most important questions concerning interior plastering: Can costs be saved by plastering yourself? The answer to this must be no. Plastering is a difficult project where a lot can go wrong. In modern plastering, special devices are used for spray plastering or machine plastering, which deliver significantly more precise results than hand plastered systems. Although the total costs are significantly lower due to your contribution, the result is only poor. For this reason, you must leave the work to professional companies so that you do not have to pay extra to eliminate defects in the end.

Tip: If you want to make small repairs to the finishing plaster, this is not a problem and can be carried out by you without any problems, because in this case you only need a small trowel and the appropriate finishing plaster. Independent plastering is also possible using a finished plaster, as this does not require any special machines for a good result.