Once wallpaper is pulled down, there is often a rough surface of glue left behind. If you don’t want to sand back the wall completely, decorative plasters offer completely new possibilities. Or perhaps you have a perfectly smooth wall already, but want to give it a plaster treatment that is unusual. The properties of the different types of plaster vary considerably. We explain what matters and how to use decorative plaster to style a wall.
The many different decorative plasters from 1 to 3 mm layer thickness are particularly interesting for self-made designers, because they represent a good and very individually designed alternative to the often reviled rough surface when you know how to use decorative plaster to style a wall.
What are the advantages of decorative plaster to style a wall?
The decorative plasters are generally considered very good for equalizing the indoor climate. This is due to the mostly mineral or clay-based ingredients, which absorb excess humidity very easily due to their fine-pored surface and just as easily release it back to the room air in times of when the air dries out.
But be careful when painting decorative plasters: The wall paint must of course be open to steam diffusion! So use only those based on silicate, glue or casein (even with the tinting colors!).
A dense latex colour would immediately nullify the moisture-balancing effect of the decorative plasters. The craftsmanship and skill required for applying the decorative plasters is very manageable for self-cleaning plasters.
Extremely important: There is an associated primer for all types of decorative plaster. You should definitely use this, which neutralizes (later translucent) color differences of the substrate, compensates for its suction behavior and significantly improves the adhesion of the plaster.
Speaking of the substrate: It must also be quite cleanly prepared for plasters and not be too uneven. The layer thickness is usually not sufficient for covering major wall defects.
You just need to stir most of the different types with water and then put it with the trowel on the wall. With the amount of water, be sure to adhere to the manufacturer’s specification so that the plaster can develop its full adhesive strength.
With the thin layer thicknesses of only 1 to 3 mm, it doesn’t matter if you start cleaning at the top or bottom of the wall. If you have never plastered before, you should practice a little on a piece of plasterboard to guide the trowel from the wrist with an smooth stroke. On the wall it is unfortunately too late to practice. So: Don’t be afraid of the trowel!
Wall design: plaster or wallpaper?
Decorative plastered walls have been on the rise for some time, many self-renoveurs prefer to work with the trowel than with the wallpaper.
The advantages of the only 1 to 3 mm thin layers are obvious: they are much harder in the surface than the paper, they can also be individually designed in colour and structure, and they have an extremely favorable effect due to their porous structure and balancing the indoor climate.
The big drawback: You can only get them back down with heavy equipment. In contrast, the dry-removable nonwoven wallpapers offer a real advantage. The only exception is the clay plaster. Because it is soluble in contact with large amounts of water, so you can wet and scrape it off.
Many of the structured plasters can also be smoothed with a filler for further construction. The wall coatings made of cotton or other textiles are almost a mixture of plaster and wallpaper.
They, too, are first mixed with water, put on the wall with a trowel and dry there to a soft, very breathable textile layer. The downside here: You need to remove this coating before applying anything else to the wall. In terms of price, the wallpaper – especially the rough fibre – can not reach the water. The most expensive are the cotton plasters with prices between $20 and $40 per sqm at the time of writing this.
How to use decorative plaster to style a wall
Before plastering, cleanly glue all adjacent surfaces with foil and tape, even those that are still to be plastered.
Preferably start at the top end of the wall with the application of the plaster. The trowel is usually pulled upwards from the bottom obliquely. Start at the ceiling, pull it down from the corner obliquely. Basically, you always work from the inner corners into the surface and from the surface towards outer corners.
The easiest way to do this is if you don’t take too much plaster on the trowel. A handful is enough. Pull the trowel over the wall quickly, not too slowly.
When you put the plaster on, hold the trowel quite steeply (about 45°) to bring it straight to grain thickness. For the subsequent “closing” of the surface, adjust the trowel a little flatter. Don’t work too slowly here either, a rehearsed swing in the arm will produce better results to use decorative plaster to style a wall
Important: Do not work from both walls into a corner. First get one wall finished, and then the opposite one so that the first can dry in peace.
If the mass has just tightened a bit, you can structure the surface with a soft bristle brush. Swipe diagonally from both sides over the plaster surface. The wetter the brush, the more of the plaster you release and the clearer the structure becomes. Do not use a synthetic or other brush, because they are all too hard – you would brush the plaster off the wall again.
If the plaster is dry, you can treat it with a wax. On the surface, water drifiens more easily and the surface remains open to steam and continues to be overworkable. Apply the wax with the brush.
For the best indoor climate: clay plaster
The clay plasters occupy a special position in the decorative plasters. Strictly speaking, this is a mixture of marble sand, plant starch, clay flour, and pigments, in which the clay accounts for at least 20% of the mass.
This proportion is completely sufficient for the astonishing abilities of clay plaster. The clay plaster is processed like all other plasters.
The only difference is that clay is and remains water soluble. This benefits you in the surface design (with brush, brush), but it is not smudge-resistant.
The clay plasters can be applied single and multi-layer and painted with the correct paint. The low layer thicknesses used in decorative plasters already offer a room-climatic improvement.
What is clay, and what makes it?
Clay is a weathering product of nature and consists of clay, sand and silt in very fine particles.
The clay minerals are responsible for the binding capacity of the mixture. Depending on the clay variety and the place of degradation, the clay often has very different compositions. The addition of sands (structural encoders), pigments, processing aids (e.g. plant thicknesses) and effect supplements such as special grains or fibers then make up the different structures and cleaning systems.
This allows very diverse types of plaster to be produced from the various raw materials, from thin-layer coating plaster to basic plaster for wall heating systems. The addition of hydraulic binders such as gypsum, lime or cement is consistently dispensed with.
The clay flours are so interesting as a building material because they can perform three important tasks within the cleaning system at once: they are binders, inking agents (fewer pigments have to be added) and filler (less marble sand) in one .
Due to its good insulation properties in combination with straw, clay used to be used as a thermally insulating filling material in half-timbered construction and because of its high raw density as sound-insulating bulk in wood-beamed ceilings.
The clay is experiencing a renaissance, especially in interior fittings: as a basic plaster (in 20 mm thickness), as a spatula plaster (1 to 2 mm thickness) and as a spreader (0.1 mm thickness). Even finished clay wall elements with integrated surface heating are finding more and more customers.
The most well-known is the ability of clay plasters to absorb large amounts of moisture from the room air. But also odours, for example from tobacco smoke, are filtered from the air in the long term.
Interestingly, this “engaging” being of clay does not work over as much layer thickness as possible, but only in the first few millimeters of the plaster. Much more important is the largest possible surface area of the clay, which is why the manufacturers also recommend plastering the ceiling – the largest free area in the room.
A lesser known property is the shielding effect of clay in radiofrequency radiation, such as mobile phones. In large layer thicknesses, a clay plaster alone can shield about 98% of this radiation. Just as effective, but more practical, however, are plasters in layer thicknesses of only 1.5 mm, which are offset with dissipating carbon fibers.
The picture shows the superficial difference between a clay fine plaster and a clay base plaster. The basic plasters are usually combinations of clay and plaster or clay and lime. Dry plasters are also available in clay versions.
Even with clay plaster you can do it colorfully
The clay plaster manufacturers offers basic colours, from which it is possible mixes your desired colour in myriad variants. Theoretically, you could do it yourself, but manufacturers will generally offer a free mixing service for larger amounts (from 30 kg). In the case of such equipment, it is difficult to mix such quantities homogeneously. You could later see the individual colors on the wall, as in the image below.
At the dealer, small colour sample cases are available from which you can choose your colour and then order it. The container price (with and without mixing) is just under $120 per 10 kg clay plaster bucket. With this quantity you can get about 14 sqm at 1 mm layer thickness. Keep in mind that you also need about 2 sqm for your practice area.
Sprinkle the dry, monochrome mixture into the amount of water indicated on the bucket and stir well.
If you want to achieve a variegated effect, take a small battof of each color on the trowel and drag it onto the wall at the same time. There you have to distribute the colors criss-cross.
Gerhardt Richter is a writer and a trainer at trade technical colleges, specializing in carpentry, plumbing, mechanics and construction.