Wall screed, its types, material selection, surface condition check, its preparation and coating device. Based on the foregoing, each of the types of plaster can be classified not only by regulatory requirements, but also by the method of its application:
- Simple plaster consists of layers of spray and primer. In this case, the priming layer is simply rubbed off, and the total thickness of the plaster layer is 12-15 mm.
- Improved plaster has all three layers, but the total thickness of the coating should not exceed 15 mm. The last covering layer is rubbed with a wooden or felt float, or with a rubber or steel trowel.
- High-quality plaster can include, in addition to all layers, an additional primer, and its application is carried out exclusively with preliminary hanging of the surface and installation of lighthouse profiles. The thickness of such plaster is up to 20 mm. Thicker coverings are made with reinforcement. When performing a high-quality screed of walls, a metal or nylon mesh can serve as reinforcement.
The choice of mortar for screed walls
For the preparation of plaster mortars, cement, gypsum, sand and lime are used. Mixtures can be made from sand and cement in a ratio of 3: 1, from sand, cement and lime - 5: 1: 1, from sand and lime - 3: 1, from lime and gypsum - 3: 1.
If the strength of the coating is given priority when plastering walls, cement-based mortars and reinforcing mesh are used. Such plaster is strong and durable, but has a rough surface. Gypsum mortars are less durable, but their use allows you to make the wall perfectly smooth.
When choosing a plaster mix, you need to pay attention to the expected thickness of the coating and the type of binding material. It is recommended to use gypsum-based mortars for finishing the walls of living rooms, since finished coatings help maintain a comfortable microclimate in bedrooms, children's rooms, living rooms, etc.
For plastering the walls of rooms with high humidity, for example, kitchens or bathrooms, it is recommended to use cement mixtures, since the coatings made with their help resist the penetration of moisture into the base of the walls and the development of mold.
Recommendations regarding the choice of a particular brand of material can be obtained from a hardware store.
Checking the walls before screed
Before screed the walls, you need to determine their irregularities. Knowing the maximum surface differences and its area, you can easily calculate the average optimal thickness of the plaster layer for the purchase of the required amount of material.
For work, you will need a two-meter building level, a rule or a plumb line. It is necessary to drive a nail into the corner of the wall of the room, its head should protrude 2-3 mm above the surface. Then you need to hang a plumb line on the nail so that its weight does not touch the floor.
After the oscillation stops, the plumb line forms a vertical straight line. Focusing on it, now you need to drive the second nail along the line into the bottom of the wall. In this case, the levels of the nail head and the plumb line relative to the wall must coincide.
The same procedure should be done on the opposite side of the wall near its corner. As a result, four nails-beacons should be hammered along the perimeter of the wall, denoting two straight lines.
To check the unevenness of the wall, you will now need a long thread, which should be pulled from the end of one upper nail along the diagonal of the wall to the end of the lower beacon located in the opposite corner. You need to do the same with another pair of nails. When fastening the threads crosswise, make sure that they do not touch the wall.
Now, using the stretched threads, you can determine all the deviations of the wall in the vertical and horizontal directions, as well as measure their values. Small defects in the surfaces of the walls can be corrected with plaster mixtures; in case of significant deviations, it is recommended to use gypsum plasterboards, which can be fixed on glue mixtures or a metal frame.
Surface preparation before screed walls
Preparing the walls for plastering is necessary to ensure the adhesion of the future coating to the base. Therefore, the success of the entire repair depends entirely on the quality of these works.
Their first step is to clean the walls from old finishes, dirt and stains of various types. Since the preparatory and plastering works are referred to as "wet" processes, before starting it is recommended to turn off the power supply of the premises for safety reasons.
The cleaning rules are as follows:
- Peeling old plaster must be removed completely. Problem spots on the surface of the walls can be identified by tapping them with a small hammer. Particular attention should be paid to this issue when planning a coating device with the help of beacons, since they must be fastened to a reliable base.
- The whitewashing of the walls is removed with a spatula or washed off with soapy water. After using the second option, the walls must be washed with clean water.
- Old paint can be removed with a special enamel remover, which can always be purchased, with a spatula, metal brush or sander.
- To remove old wallpaper, you must first wet its surface, and then remove the material and the adhesive layer with a scraper.
- Wall stains are removed using a variety of chemicals, the composition of which depends on the nature of the pollution, for example, grease stains, soot or rust.
- If mold or mildew is detected on the walls, the surface should be treated with an antiseptic.
A prerequisite for a reliable fixing of the plaster is the roughness of the walls. Depending on the material of their manufacture, this property can be given to the surface in various ways:
- On smooth concrete walls, frequent notches of small depth are made with a chisel or ax.
- In brick walls, for this purpose, part of the old mortar is removed from the joints between the bricks. This procedure is easy to carry out with a metal brush.
- Wooden walls are sheathed with thin wooden slats (shingles) or metal mesh.
- The joints of wall sections, consisting of materials of different texture, are reinforced with strips of reinforcing mesh, their width should be at least 200 mm. When reinforcing the wall screed with a mesh, it should not touch the base surface.
Preparation of walls for plastering should end with their priming. This process is intended to provide additional adhesion to the materials and to remove dust from the substrate. The primer must have good penetration and strengthen the surface of the cleaned walls.
For loose walls, emulsion primers are ideal, and universal formulations are used for all types of wall materials. The primers are applied with a roller, brush or spray in 2-3 coats. Each previous layer must dry before applying the next one.
After preparing the surfaces of the walls, you can start plastering them. This process is simple, it consists of the selection of the necessary tool, the installation of beacons, the preparation of the plaster mixture, the throwing of the solution, the leveling of the surface and its grouting.
Selection of tools for screed walls
To successfully complete the wall screed with your own hands, you should stock up on useful tools. These include:
- A painting bucket and a trowel, which is also called a "trowel" and is a heart-shaped metal blade. Both tools are designed for throwing plaster onto the walls.
- Roller and brushes. They are needed for priming the surface. It is convenient to handle continuous areas with a roller, and hard-to-reach areas with brushes.
- Rule. The instrument is constructed as a wide 2-meter aluminum bar, often equipped with bubble levels. It is used to level the applied layers of plaster or gypsum mixture.
- A grater is a wooden shield with a handle attached to its plane. It is necessary for smoothing the solution applied to the surface and finishing the wall. The working surface of the grater is often covered with felt or felt to improve the finish of the mix.
- Building level and plumb line - these devices are necessary when installing beacons before plastering walls.
In addition to the above tools, you will need a container for mixing the solution and a shovel. If a concrete mixer is available, this will greatly facilitate all the work.
Installation of beacons for screed walls
Lighthouses are designed for laying the plaster layer on one common level relative to the base. Their use allows you to adjust the initial thickness of the coating, as well as to perform work efficiently and quickly.
Lighthouses can be boards fixed to the wall, nails hammered into it, cones thrown from mortar or metal profiles. Lighthouses of any kind are set strictly according to the level. The best option is, of course, lightweight metal T-sections.
To mount the lighthouse profile on the wall, you need to draw a strictly vertical line, and then drill several holes along it, the diameter of the drill should be more than 10 mm.
After that, it is required to hammer wooden pads at the level into the holes obtained, and screw the lighthouse profile to them with screws. To ensure its stability, the locations of the pads should be cemented.
The beacon method of plastering is indispensable, if necessary, in a thick layer of coating. The distance between the profiles is chosen 10 cm longer than the length of the used rule.
Wall screed technology
For the preparation of any plaster mixtures, there are general recommendations:
- Dry mixtures must be sieved through a sieve with a mesh size of 5x5 or 3x3 mm before use.
- The depth of the mortar box should be 10-20 cm.
- Stirring is carried out with a meter wooden paddle until a uniform consistency of the solution is obtained.
- The prepared mixture should have a normal fat content, that is, it should stick slightly to the oar.
- If the sticking is excessive, a filler is added to the solution to reduce the fat content of the mixture. If the adhesion to the oar of the solution is weak, you need to add an astringent: cement, lime, etc.
Plastering work should be carried out at an air temperature of at least + 20-23 degrees and its relative humidity up to 60%. If this rule is neglected, the plaster can crack and peel over time.
The distance from the outer surface of the lighthouses to the base of the wall is the total thickness of the soil and spray layers. The last layer of the cover is masked by the lighthouse profiles. Sometimes they are removed from the plaster, and then the gaps formed after this are sealed with a solution. But these actions can break the solidity of the coating. Therefore, it is recommended to leave them, since such profiles serve as a kind of reinforcement that strengthens the plaster.
The mortar is thrown on the walls between the beacons using a trowel or bucket. The mixture is placed on the walls from the bottom up. The trowel, filled with mortar, is brought horizontally against the wall and then rotated 45 degrees with a sharp upward motion.
The priming layer is sketched just above the surfaces of the beacons. After raising the plaster layer 50 cm from the floor, the application of the solution stops, it is the turn to use the rule.
Its horizontal, sharp reciprocating movements go from bottom to top. The rule moves along the beacons to the end of the area covered with mortar. The repetition of the movements occurs until the mixture layer is completely evened out. Then the whole process is repeated: the site is then thrown with a solution 50 cm up, and then it is aligned with the lighthouses by the rule. The procedure continues until the wall plaster reaches the level of the ceiling.
Grouting the cement screed of the walls is carried out after incomplete drying of the surface or the next day. In the second case, the plaster will need to be moistened with water. Work is done using a circular motion with a paint float. They should be repeated until the surface to be treated is perfectly flat.
Important! To prevent the solution from sticking to the tools during work, they must be periodically moistened. How to make a wall screed - watch the video:
After finishing the plastering of the walls, it must not be allowed to dry quickly. On hot days of the summer period, it is recommended to slightly moisten the coating in order to avoid cracking on it. Good luck!
