Plastering exterior walls has several advantages. The plaster forms a good basis for further surface treatment with lime, felt or paint. The house brightens up and the facade becomes more even, creating a more peaceful expression. In addition, it may be easier to repair a plastered surface than a bare wall, since damage to a bare wall often requires the stones to be replaced or refocused.
Prepare the facade
You get the best result if you make sure that you prepare the walls well for plastering.
1. The walls to be plastered with lime mortar must be absorbent, ie with an open surface to which the mortar can adhere. If the façade is painted with impenetrable paint, these must be cleaned to a solid basis. Cleaning is done by washing under low pressure, where possible.
2. In the case of damaged joints or bricks in the wall, these will be repaired or carved and new bricks will be placed.
3. Thoroughly clean the brickwork to remove dirt and dust. For this you can use soapy water or groundwater that is specially made.
4. Connections are refilled if necessary and all connections are compressed with a connecting piece.
Before you start plastering, you must water the base to ensure it has an even absorption capacity. This applies to every layer of plaster that you apply.
The plasterer work
When plastering a facade, the most important thing is to get an elastic surface to prevent cracks in the bonding zone. At the same time, the mortar must be strong enough to adhere well. You can achieve this combination of properties by plastering the façade in several layers, using the strongest mortar and applying the thickest layer on the inside, using the weakest mortar and applying the thinnest layer on top of the inner layer. If a plaster layer has already been applied to the wall, the layers that you add on top cannot be stronger or thicker than the inner layer. Otherwise it probably won’t attach.
If you want to plaster a rough wall, start with rough casting with a clean Jurassic mortar Kh 100/400, ie you apply a thick layer of mortar plaster and leave it with a rough surface. Then you apply a weaker mixed mortar, for example KKh 20/80/475, to form a coarse textured façade using a steel plate. Finally, use an even weaker mortar, such as KKh 35/65/500, to create the final finish with a thin layer of mortar.
The grain size of the sand determines how thick a layer of mortar you can apply. As a basic rule, the thickness of the layer is 3 x grain size. So if you apply thinner and thinner layers of plaster with increasingly weaker mortar, the grain size in the mortar should decrease.