- Materials and tools
- Preparing walls for plastering
- Clay plaster preparation
- Plastering works
- Treatment of plastered walls and their further finishing
Recently, the use of natural materials in construction has become very popular. This article will focus on clay plaster as a material for interior decoration and insulation of the exterior walls of the house, as well as on the features of its application using plaster beacons.
This technology, which has been known for many centuries in Ukraine, is again becoming popular throughout Europe. And although in Russia until recently, clay plaster was used mainly for utility rooms, some housebuilders are beginning to successfully use it for finishing residential buildings..
The main advantages of clay plaster are:
- its high thermal insulation performance and at the same time excellent vapor permeability, in other words, it “breathes”, and during air circulation, the material is able to absorb excess moisture from the room, and if it is too dry, give it back;
- clay has antibacterial and preservative properties, therefore, mold or mildew will never appear on walls covered with clay plaster, and the material of the walls, especially wood, does not require treatment with antiseptics;
- it is a durable and easily recoverable material that is not afraid of temperature extremes and high humidity, and a separate section of the wall can be replaced without affecting the rest of the coating;
- clay plaster can be applied on any surfaces, due to its high adhesion, it is well applied to wood, brick, concrete and just on straw;
- clay does not burn, it can easily withstand temperatures over 1000 ° C, and at the same time protect flammable materials;
- and what is important in any construction – clay plaster is economically profitable, in comparison with common plaster mixtures, its use allows to halve the cost of interior decoration of the house.
The disadvantages of clay plaster are much less, and they are mainly associated with technological nuances:
- due to the peculiarities of the composition of natural clay, it is impossible to create a single recipe for a plaster mixture, in each individual case it may differ;
- the surface of the clay plaster has a non-uniform texture and without fail, even under the wallpaper, a finishing layer is required;
- difficulties in finding a specialist for wall decoration, since few craftsmen are familiar with this material.
Materials and tools
To prepare a plaster mixture for leveling walls you will need:
- natural clay without impurities (sieved)
- river sand
For the second layer of clay mixture you need:
- pure natural clay
- river sand
- edible salt
To knead and apply clay plaster you will need:
- concrete mixer
- Master OK
- plastering rules
- plumb line
- galvanized plaster beacons
- molding plaster (for fixing beacons)
- screws and dowels
Preparing walls for plastering
Despite the fact that clay has good adhesion, it has a much higher weight, in contrast to gypsum mixtures, therefore, for more reliable adhesion to the surface, it is necessary to remove the remnants of old plaster or cement mortar from the walls, slightly widen the joints and treat the surface with a primer.
After that, the walls are marked, in which the attachment points of the beacons are indicated by straight vertical lines. The first line should be about 20 cm from the corner.
At the top and bottom of the wall along each marked line, we drive in a dowel-nail and set the level without screwing in the screws. Using a vertically stretched thread and a level, we check the plane of the walls. If there are small protrusions – knock them down, if large ones – we take them into account when installing beacons: the minimum thickness of the plaster layer should be flush with the maximum point of the protrusion.
We install standard plaster beacons with a height of 6 and 10 mm according to the level. In places where the plaster layer will be thicker, crumb with a height of 10 mm is used, and for a thinner plaster layer – 6 mm high. To do this, we cut off the required length of the plaster beacon and put it on the plaster mix, pressing a little until it rests against the caps of the screws. The distance between the beacons depends on the area of the walls, their evenness and the length of the rule.
Clay plaster preparation
Mixing clay mortar is a very time-consuming process, so it is best to do this with a concrete mixer. The content of clay is regulated by the amount of sand and depends on the properties of the clay itself: if it is very plastic, or as they say “oily”, it can crack when it dries. If the clay used is sufficiently plastic, the solution for one batch is prepared from the calculation:
- 2 buckets of clay
- 6 buckets of sand
- 6 buckets of sawdust
You can determine the plasticity (fat content) of clay in the following way: after making a ball from slightly soaked clay, you need to put it between the planed boards and press down on top. With a high fat content of clay, cracks of half the diameter are formed on the ball, with medium plasticity – by a third of the diameter, and if the clay is completely skinny, then the ball will not form cracks, but will completely fly apart. This property of clay is taken into account in the preparation of plaster. In a solution with oily clay, the amount of sand increases, and can reach the ratio of clay and sand 1: 4 or 1: 5, and with low plasticity of clay, the amount of sand is usually used in a ratio of 1: 2 or 1: 3.
In order for the plaster to have a low thermal conductivity, a filler must be added to it. In this case, sawdust is used as a filler. Moreover, they are analogous to the plaster mesh, since the solution, thanks to the filler, will be well reinforced and prevent the plaster from further cracking..
After pouring clay into the concrete mixer and pouring it with a small amount of water (1-2 buckets), we leave it to soften for 5-10 minutes. Then we add sand, sawdust and gradually adding water, bring the solution to a uniform consistency of any plaster mixture (like thick sour cream).
For the second layer, the clay solution has a slightly different composition:
- 2 buckets of clay
- 6 buckets of sand
- 100-200 grams of table salt
This solution is prepared according to the same principle in a concrete mixer, only instead of a filler, ordinary edible rock salt is added to it for strength.
Plaster is applied in two layers: the first is a rough layer and the second is for finishing. The first (leveling) layer of plaster is applied between the beacons. After throwing the clay mortar on the wall with a trowel, the surface is leveled using the rule from the bottom up. In this case, the leveling layer of plaster is applied between the beacons using the rule of shorter length, or the same, but in this case the movements are made at an angle. It should be noted that for good anchoring on the wall, the minimum layer of plaster should be 2.5 cm.
The second layer is applied after the surface of the first has dried. The drying time of the first layer depends on the thickness of the cast, air temperature, ventilation. Usually in hot and dry weather in a well-ventilated area, the first coat is ready for application after 2 days. With high humidity, as well as in winter, this process can take a whole month..
The second layer of clay plaster is applied over the lighthouses themselves, touching their edges with the rule. If cracks appear on its surface during the drying of the first layer, they are rubbed with this solution using a grater. Dry plaster does not require any treatment before applying the second layer. On the contrary, small irregularities when applying the second layer will only increase the degree of adhesion of the plaster..
After the second layer has dried, the beacons are carefully removed, and the grooves are filled with clay solution. While some professionals prefer to leave the beacons in the plaster, in the experience of many home builders, it is best to remove them. This is due to the fact that often when the lighthouse rule is maintained, the top layer of galvanized steel is removed, and the lighthouse begins to rust as the plaster dries. Subsequently, traces of rust from such a lighthouse begin to show through the wallpaper and even resistant paint. The second reason for removing beacons is the likelihood of cracking of the plaster if a screw hits the beacon, if you suddenly have to fix something on the wall. Also, some developers have noticed cases when over time the lighthouses began to protrude from the surface of the wall. This is usually due to the fact that plaster, especially for gypsum mixtures, tends to shrink when dry..
After the final drying of the plaster, the entire surface of the plaster must be rubbed with a broom brush and floor polisher. At the same time, first, the wall is sprayed with a well-moistened cloth, and then rub it with a floor polisher in large circular movements.
Treatment of plastered walls and their further finishing
After grouting and complete drying of the plaster, a final (finishing) wall decoration is performed. Drying should take place in natural conditions, excessive, intensified drying with heating devices or a building hair dryer, can cause cracking of the clay.
Since clay plaster has a composition prone to shedding, its surface must be additionally treated with a deep penetration primer before painting or wallpapering. If you plan to paint the walls, then for a perfectly smooth surface, putty is made with a thin layer using gypsum mixtures. Fans of national flavor can give the room an ethnic Ukrainian style by whitewashing the walls several times with lime. It is also practiced to decorate the walls with decorative clay plaster, which, using dyes, gives the necessary shade and the surface can imitate natural cracks, brick or stone.
Clay plaster has another advantage – a very low cost, about 15-20 rubles. per square meter of plastered surface. This cost does not include the wages of a specialist, since in each case it may be different. Moreover, having mastered the method of throwing plaster and using the rule, you can do all the work yourself, the most important thing is to correctly set the beacons.