This is how concrete is plastered

Concrete in private house construction is still not so common despite its excellent properties. But that changes from year to year more and more in favor of concrete walls. Thus, the plastering of concrete is becoming increasingly important. Below you will find important information about plastering concrete.

Why concrete has so far prevailed poorly

The main reason why bricks are preferred to concrete in private construction is the cost. As far as the functional properties of concrete are concerned, they are much more advantageous than with other masonry. There are also other advantages of the concrete:

  • high load capacity (especially pressure load)
  • pour easy processing already at the concrete
  • Implementation of difficult architectural specifications easy to perform

Constantly growing popularity of concrete

These are some of the reasons why more and more private builders are turning to concrete, especially for exterior walls (facades). With regard to non-supporting partitions, on the other hand, elements in dry construction are preferred. Only with load-bearing inner walls is concrete used more and more frequently. Here, the concrete used can be distinguished mainly according to the production and the recipe:

  • lightweight concrete
  • normal concrete (ready-mixed concrete)
  • In-situ concrete or construction site concrete
  • concrete blocks

Different types of concrete

Even if the material structure has significant differences and also concrete joints are added, all types of concrete have in common that they are only very slightly water-absorbent. In addition, a special feature that must be taken into account for plastering, the poor drying of concrete (from the inside out), due to the poorly developed capillary system.

Special features when plastering concrete

Therefore, when plastering, it must be ensured that the concrete gets enough time to harden and dry out. The thicker a concrete wall is, the longer the time is left to wait.

Prepare concrete for plastering

Can then be plastered, the subsoil must be very well prepared. The following points must be observed. The concrete must be free from the following residues:

  • dust
  • dirt
  • fat
  • Release agent (residues from stripping from the concrete, for example)
  • humidity

Concrete blocks (lightweight concrete)

Although lightweight concrete blocks are slightly absorbent, they have a rough surface. Therefore, the plaster can later interlock well with the concrete blocks. A pretreatment of lightweight concrete blocks is therefore not mandatory, but can be carried out.

Conventional concrete

This looks different with conventional concrete (transport as well as in-situ concrete). Also this concrete is weakly absorbent, as we have already described. In addition, the surface is very or relatively smooth, so that plasters are difficult to adhere. For concrete surfaces made of cast concrete, this always presupposes that the substrate is prepared accordingly.

Preparation for plastering concrete: bonding agent

Thus, a suitable bonding bridge must be applied with the tooth trowel. In the grooves of the concrete, the thickness (plaster coverage) must be at least 2 mm. Before the actual plaster can then be applied, the bonding layer must be able to set and harden accordingly. Under favorable conditions, this is at least two days. As a rule, however, significantly longer waiting times can be expected. The bonding layer must be applied with a tooth trowel.

Preparation for concrete plastering: adhesive mortar (plaster mortar)

There are also single-layer, special adhesive mortars offered. These are made on the basis of lime and cement. These plasters are a bit more expensive, but have (in the interior) compared to gypsum plaster) the advantage that the residual moisture content of the concrete does not necessarily have to be below three percent. In addition, no further waiting and service lives have to be taken into account - only the information given by the manufacturer regarding the product must be followed in this regard.

Processing from plaster

Both options for plastering concrete allow the use of conventional plaster for manual application, but also the spraying of machine plaster with a cleaning pump.

Tips & Tricks

The plastering of concrete does not always correspond to the actual wishes of many builders. Instead, a trend towards fair-faced concrete is evident. To do this you first have to sand and then polish the concrete. Even when boarding, this design must already be considered during the planning phase. In addition, exposed concrete should preferably be further protected. For this you can seal or impregnate the concrete.

Video Board: cement plastering tips techniques