Facade plastering

Facade plasters for facades and plaster renovations

Facade plasters are strong in fashion, but often we are confronted with errors in the execution, the preparation of the substrate, the choice of the plaster or the detailing. It is a shame, because that leads to inferior results that are unworthy of a facade plaster. That is why it does not seem to us a superfluous luxury to go a little deeper together with Bob Gall, technical manager of Knauf, to go into the different types of exterior plastering and to put the finger on the wound of a number of common mistakes.

Mineral plasters versus synthetic resin patches

There are many different types of plasters on the market. Grosso modo can be divided into two groups: the mineral plasters and the synthetic resin patches. Those who like a tight, smooth surface will be more likely to be found for a synthetic resin patch than for a mineral plaster. Mineral patches based on cement are usually rougher, although flat mineral patches also exist. In addition to the , there are also thicker mineral patches, such as the scratch patches. You don't have that with synthetic resin plasters that are always applied thinly. For this type of plaster, an even surface is a must. Mineral plasters are usually less water-repellent than the synthetic resin patches. On the other hand, it is true that mineral patches have a self-cleaning effect. The dirt is rained, as it were.

Among the mineral plasters we also distinguish the scratching and sanding plasters. This difference has only to do with the way of application and the view, not with the quality or other properties. It is wrongly assumed that the grain size determines the degree of pollution. Flat patches with a thin grain size would be less likely to pollute than rough patches with a thick grain size. Wrong. Just look in Germany where usually a grain size of 6 mm is used and the plasters do not pollute faster than with us. Also remember that mineral plasters are water-repellent, but not waterproof.

Detailing the facade and plasterwork

If a facade plaster becomes dirty and shows annoying stripes, it usually does not have to do with the , but with the detailing of the facade. Villages must be at least 3 to 4 cm compared to the facade. The sides must be provided with a raise (with silicone or mechanically sharpened) to direct the water to the center of the sill. Also pay attention to the location of the ventilation grilles. The outflowing air should not be discharged directly against the patch. Also make sure that the grids either can be far enough or do not leave out at all.

Ground for plasterwork

A proper study of the substrate is a must. To absorb tensions, the plaster must be less hard than its surface. For certain substrates, a lime cement plaster must therefore be used instead of a cement plaster. Knauf has a modified plaster for most substrates, but for a number of specific cases (e.g. wood wool cement boards, polystyrene plates), it is advisable to contact our technical service for an advice regarding the pre-treatment of the substrate. A little stable surface can be picked up with a metal plaster carrier or reinforcement.

Facade plinth for facade plaster

Too little attention is paid to skirting boards. Too bad, because because that sometimes gives the facade plaster a negative view that it does not deserve. To avoid stains by and , a plinth of at least 25 cm is recommended consisting of natural stone or a dark plaster without lime. A plinth can also prevent mechanical damage.

Lime blooms in plasterwork

At low outdoor temperatures and a humid climate, lime blooms can occur if colored mineral patches are used. That occurs when there is a lot of in the that comes out due to vapor pressure. It is therefore advisable to apply these patches only at normal temperatures and dry weather. Due to time and rain, they usually disappear or a treatment of the surface with an appropriate paint can also eliminate the .

When to apply a facade plaster?

In Belgium, one is often far too fast with the application of the patch. One would still have to wait at least a year so that the building has the chance to work. Otherwise, cracks will occur that also continue in the facade plaster. Weather conditions are also important. Only when the temperature is at least two days between + 5 and 30 °, plaster may gepleisterd be made. Also heavy rainfall or heavy sun raid is bad for a good placement.

Profiles and plasters

Do not save on the quality of the profiles. There are several possibilities: made aluminum, stainless steel or galvanized profiles with a PVC sheath that are available in various colors. This sheathing also ensures that the galvanizing layer is not damaged by scratching.

Colours for plastering and facade renovations

Especially when you work with a facade insulation system, it is advisable to choose light . With dark colors you can get too large thermal stresses and therefore cracks. If you choose a colored patch, make sure you order everything at once so that no color differences can occur. Choosing colors is not easy. Do not only rely on the color chart, but if possible, first look at a realization that has already been carried out with a certain shade.

Protection of windows and doors for plaster walls

There may be more discussions about damage to other parts of the house than about the quality of the facade plaster. So make sure that everything is very well protected and adhered. This way you avoid useless discussions.

Facade insulation systems for plaster walls

More and more people switch to where an is applied to a single wall and the plaster to it. An important advantage of this is that you do not need , that the absorbs a lot of stresses of the masonry and that this reduces the danger of . This way of working should be considered as a complete system in which all parts are coordinated. It is not recommended to mix parts of different brands and systems.

ATG approval : The facade insulation system and the products of Knauf that are processed herein have an ATG approval. Not unimportant, because this is a guarantee of the decent quality. Preferably two-layer plaster systems

Most Knauf decorative plasters are applied to base plasters. So we work in at least two layers. Only for a number of rustic scratch patches that are applied quite thick, a one-layered plaster can be an interesting alternative. With single-layered systems, the danger is also greater that the implementation will be inadequate. A homogeneous masonry is an absolute must for a single-layered patch.

Training and further training are essential for a plasterer

Applying a is a style apart. A plasterer cannot just switch from the ceiling work to the facade plaster without a proper education. That is why Knauf has developed a training center where customers can learn the tricks of the trade. Also keep in mind that the market of plasters is constantly in motion. To stay informed of the latest developments, regular further training is not a luxury. You can also go to the training center of Knauf for this.

Machine processing of plaster is a must for good plaster quality

Not only because of the efficiency but also to obtain a constant quality and a consistent mixture, the machine application of a facade plaster has become a must. For this you have the choice of an extensive range of professional PFT devices. There are devices that you can use for both indoor and outdoor plasters, such as the G4 and the G5.

An ideal machine for those who sometimes alternate the classic ceiling work with the application of a facade plaster. However, companies that mainly focus on facade plasters are better served with specialized machines such as the ZP3V and the OMD. With regard to machine processing, a distinction is made between open and closed systems. Most plasterers still work with closed systems (e.g. G4 and G5) where pumping and mixing is done in the same machine.

In addition, you have the open systems (e.g. OMD or combination of G4 and ZP3) where you have another machine or unit for mixing and pumping. With this method, thanks to the name, you get an certainly benefits.