Plaster is one of the most popular facing coatings. However, if it was grossly violated technological process or negligence in operation, damage occurs of various nature: cracks, shedding, peeling.
From this article, the reader will learn why plaster cracks when it dries, the causes of defects and methods for eliminating them. As well as the sequence of processes for repairing the plastered surface of walls, both inside the building and the facade.
Technological causes of defects
Violation of proportions when preparing the solution or technology for its application, as well as errors in preparing the base, lead to the following defects.
| Defect | Cause of occurrence | Repair method |
| Blistering of the plaster surface, the appearance of small tubercles | Used unseasoned lime mixture with unquenched particles | Let the solution sit until the lime is completely extinguished, reveal the defects, moisten the surface generously with water, fill the cavities with the solution and grind. |
| Sedimentary cracks | Poor mixing dry plaster mixture, using a solution with an excess of binder for the cape | Accurately follow the proportions and dosage indicated on the package, mix thoroughly using a construction mixer |
| Peeling a fresh sketch from the base | The base is not rough enough, very dirty and dusty, the surface is excessively dry | When repairing facade plaster, the technology involves notching or filling shingles, the surface is cleaned and dust-free with damp sponges and additionally moistened with water. |
| Propagation of cracks throughout the entire depth of the plaster layer | The base material is not rigid enough, at the points of contact between two monolithic structures no reinforcing mesh | Each subsequent layer of finishing should have slightly less strength than the previous one (add less binder to the mixture), the intermediate layers should not be allowed to dry out, and before plastering, moisten the base generously with water |
| The appearance of efflorescence, spots and streaks on the surface when drying | Applying plaster to wet surface(especially relevant for external walls) | Plaster only dried walls, prevent “pull-up” of moisture from the ground by making appropriate waterproofing |
For local repair of wall plaster in some places cracks and potholes are cleaned of crumbling particles with a stiff brush, then the exposed surface is generously coated with primer deep penetration. The complete drying time is indicated on the packaging and different manufacturers it may vary, although it rarely exceeds 3-5 hours.
Repairing a crack before repair
The covering layer applied to the cracks is rubbed down carefully, flush with the general level; it is advisable not to allow the solution to spread over the previously treated surface.
Fresh plaster with small cracks scattered at a slight distance from each other is being rubbed over the entire area. To repair monolithic plaster, a cement or lime-cement mixture is diluted. Sand of fine fractions with a grain size of 0.3-1.2 mm is used as a filler.
Cleaning, dust removal of cracks
Important: When repairing, gypsum cannot be used in grinding solutions, as it loses its properties during the process. As a result, the surface may fall off in layers.Plaster repair interior walls surface grinding method:
- The surface is wetted with water;
- Put a little repair mixture on a grater;
- Apply to the surface of the crack in separate strokes;
- The grater is cleaned, moistened with water, work area spray with a brush;
- The solution is distributed thin layer along the crack using a grater in a circular motion.
Cracks appear when drying
There is another possible reason why gypsum plaster cracks when it dries. The point is non-compliance with temperature and humidity conditions. According to SNiP 3.04.01-87, as well as the German standard DIN V 18550:2005-04 for insulating and finishing coatings, most popular gypsum plasters Knauf companies must dry at a temperature no higher than 18-20°C, and humidity: walls up to 8% and air 40-55%. It is very important not to provide intensive ventilation in the room.
Surface cracked due to drying out from overheating
For cement compositions The drying rate under optimal environmental conditions is different, and also strongly depends on the type of base. There may be many more options for why the plaster on the walls is cracking.
Sand-cement and heavy decorative plaster on brick and concrete base to avoid cracking it should dry at a temperature of 15-25°C and relative humidity air no more than 75%. At the same time, the duration of drying depends on the wall humidity of 5-15%, up to a quarter of the entire period. Therefore, a 2 cm layer can dry from 18 to 30 hours.
Important: to avoid cracking of the plaster after finishing finishing works The temperature and humidity conditions in the room should be strictly observed.Local defect repair
Grouting cracks with repair compound
Repair old plaster is carried out in several stages:
- Checking the surrounding layer, removing the lagging part;
- Cleaning and widening of cracks;
- Primer;
- An intermediate layer is applied repair staff into a crack 2-3 mm below the general surface of the wall;
- While the mixture has not hardened, a mesh is applied to its surface with a spatula to improve the adhesion of the decorative layer;
- After the repair mixture has dried, a decorative finishing layer is applied, which is given the appropriate texture.
This sequence of actions is suitable for repair decorative plaster with a uniform pattern.
Important: restoration or repair Venetian plaster much more complex, since it has a multi-colored surface with a chaotic pattern. In case of noticeable, albeit local, cracks, it is recommended to finish the entire wall.Each room or apartment requires a careful, economic attitude. It is important to whitewash the ceiling, floor, frames on time. Repair work medium weight easy to do with your own hands.
How to seal plaster?
First of all, determine whether the plaster is firmly attached to the base. This can be determined by tapping the walls or ceiling with a hammer. If a dull sound is heard during tapping, it means that the adhesion strength of the plaster to the base is insufficient. In marked places better plaster beat off.
Plaster defects are removed or repaired as follows:
1. Clean the surface from which the old plaster has been knocked off, or the area from which the plaster has fallen off, thoroughly with a scraper, lightly moistening it with water to avoid excessive dust and contamination of the room.
2. Apply pre-prepared plaster mortar. The solution is being prepared of various compositions depending on the surface on which it will be applied (composition of solutions for plastering walls - see below).
Mix the indicated materials thoroughly with water until a creamy mass is obtained. It is best to apply the solution by hand wooden device, called a “falcon”, and a metal spatula - a “trowel” or an ordinary children’s spatula with a flat surface. The solution is placed on the “falcon” and sprayed onto the wall with a “trowel”.
3. After spraying the solution onto the wall, level it evenly over the entire surface to be repaired with a special wooden trowel. Move the grater from bottom to top, then zigzag your hand left and right. This helps to distribute the solution evenly over the surface so that it is more effective fix loose plaster.
Composition of mortar for plastering walls
The following compositions are used for stone surfaces:
1) mix from 1.25 parts by weight to 1 part by weight of lime and 3 parts by weight of sand;
2) 1 part by weight of lime, 0.4 parts by weight of clay and 5 parts by weight of sand;
3) 1 part by weight of clay, 3 parts by weight of sand and 0.5 parts by weight of fibrous additives (any highly crushed rags).
For plaster concrete surface take a solution of the following composition:
1) 1 part by weight of cement, 4 parts by weight of sand, 0.2-0.3 parts by weight of lime;
2) 1 part by weight of cement, 1 part by weight of lime and 6 parts by weight of sand.
For a wooden surface, mix:
1) 1 part by weight of lime and 2 parts by weight of sand or 1 part by weight of lime and 2.5 parts of sand;
2) 1 part by weight lime, 3 parts by weight clay, 3 parts by weight sand and 3 parts by weight fiber additives.
Tools for repairing cracks in plaster
Where to start repairing plaster walls? This question is asked by everyone who for the first time decided to carry out major repairs in their house or apartment on their own.
Preparation
Removing old coating
The first step is for you from the entire area that you plan to renovate. Then the masonry seams are cleared to 1.5-2 m, the surface is washed with warm water.
Installation of beacons
If the area planned for repair is large, layers should be applied along beacons to obtain the desired result.
The distance between the beacons is set so that the solution can be placed between them as a rule. The thickness of one beacon should not exceed the thickness of the plaster without taking into account the covering. Instead of beacons, part of the old strong finish can be used.
Leveling by rule
Depending on the season there are. For example, in the dry and dry summer hot weather the surface must be periodically moistened so that it does not dry out too quickly.
Defects are usually eliminated with a brick, a scraper or the end of a dry tree. Wall repairs in wooden house can be produced with lime mortar, but in wet rooms a more complex cement method plaster.
Protruding corners can be repaired with gypsum mortar, which has the property of rapid hardening. To do this, clean the area to be repaired from any remaining solution and dust, periodically wetting the surface with water. Then apply the plaster mass with your own hands and carefully level it into the correct corner shape.
Note! You can determine the area where the plaster has peeled off by lightly tapping it.
Restoring plaster
Corner finishing technology
If grease stains or soot stains have formed on the surface, they must be eliminated as a priority, before painting and wallpapering. Rust can be eliminated with a three percent solution of hydrochloric acid, fat - two percent.
Rust is also removed with a solution copper sulfate, whitewash or special paints.
The repair school advises that plastering of walls in the presence of uneven surfaces should be carried out after applying leveling putty.
Most often, the damaged area is cut so that the hole has the shape of a rectangle. The surface is thoroughly cleaned of dirt and dust and then moistened with soda solution.
If the place to be repaired occupies a considerable area, prepare gypsum adhesive mastic, which is applied to reverse side triangle in the shape of a pyramid.
For those wondering where to start repairing tiled walls, we recommend checking out finishing material for strength. If you cannot carefully remove the damaged tile, you should knock it out in small pieces. This is done gradually from the middle to the edges so as not to catch or damage the edges of neighboring tiles.
In places where windows are connected under a layer of plaster, you can use double-sided foam tape. New tiles are glued with special glue on casein-cement mastic (price - from 280 rubles), proportions 1: 3: 1: 2.5 - dry casein glue, cement, sand, water.
Some advice on how to repair a cracked wall.
- Apply primer and let it dry for 2-3 hours. Then carefully sand the surface so that it is perfectly smooth and even.
- Next, the surface will be coated on top. Apply with a spatula cement mortar and let it dry.
Align
Repairing cracks
April 23, 2014The walls have begun to crumble, the plaster is falling off in pieces - all this can be fixed!
Let's break the process into two stages. Let's start work with preparation for wall repairs, and the repair work itself.
First stage. We will remove damaged sections of the walls. As a tool, you can take: a hammer, an ax, a scraper or an electric hammer.
The preparation process itself is very dusty, so it is worth wearing dust protection. Working clothes won't hurt either, especially good gloves.
When removing plaster that has reached the end of its useful life, it should be done with small blows to the wall. Cases where neighboring areas disappear on their own cannot be avoided in any way. Therefore, we carry out the work according to the easy principle - what is missing is gone. There is no need to feel sorry for old plaster.
Having covered all the defects in the walls, you can begin priming the walls. special composition, which can be bought at any hardware store.
Primer is necessary special tools, a roller or brush is best. You need to saturate the walls carefully, allowing the composition to be well absorbed into the base and adhere to the wall. After finishing the priming process, let the treated walls dry.
The preparation process is complete, you can proceed to next stage wall repairs
Second phase. This stage is completed by sealing defects in the old plaster, special mixtures, solutions.
Determine which mixture is suitable the best way, you can know the thickness or volume of damaged sections of walls. In a hardware store, sellers will conduct a short consultation on selection the required material for repair.
Solutions for wall repairs must be applied with narrow-purpose tools. The following types of tools are suitable for this stage of work: spatula, half-grater, trowel, rule.
The prepared mixture is applied in two or three stages, each stage includes complete drying of the solution and the application of a mesh for reinforcement. It is necessary to reinforce the walls to obtain further good results.
The last process of wall repair will be grinding the applied mortar in damaged areas of the walls. We will need: sandpaper or mesh with abrasive coating. Sanding walls, necessary stage completion of damage repairs. It is not always possible to cover the areas of the walls being repaired evenly; this requires sanding.
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At major renovation walls, first of all, you should think about plaster. It can be completely dismantled and replaced, or you can simply patch it up. Let's look at how to repair plaster on old walls.
Replacement
Repair of plaster begins with its inspection. After all, it is necessary to redo not only the fallen areas, but also those where greasy spots or fungus have appeared:
- Once you have identified the work area, you will need to remove the old plaster layer from it;
- After this, they clean the masonry seams for about two meters and wash everything with warm water;
- Plastering is carried out in three steps. First, the wall is wetted, then primed, and after that a new layer of mortar is applied with your own hands. For large areas, masonry is done using beacons. The beacons are located from each other, at a distance according to your rule, as shown in the photo. In this case, it is necessary that the edges of the rule lie on the surface of the beacons when editing the solution. If the area being treated is not too large, then the edges of the old layer can serve as beacons.
Considering the time of year in the yard, plaster has its own nuances. At high temperature outside the window, fresh solution must be wetted from time to time, otherwise everything may crack. If defects are found, they can be removed with a scraper or a piece of brick.
For plaster wooden surfaces used mortar, but here are the rooms with high humidity require use cement mixtures. For protruding corners, a gypsum-based solution is used. It has a quick setting effect. The corner is cleaned of dust and dirt, moistened with water, a pre-mixed solution is applied and the corner is given the correct shape.
To find an area with a loose layer, use a hammer or wooden mallet. The entire surface is tapped, and a dull sound will indicate exactly where the finish has come off.
Restoration
In addition to peeling and destruction, the plaster layer may have other defects that will require repairs to the plaster of interior walls. Over time, stains of grease and soot appear on the wall:
- Before applying paint or wallpaper, they must be removed. Oily stains removed with a two percent solution of hydrochloric acid;
- But for rust you need a 3% solution of the same acid. In addition, copper sulfate will help get rid of rust;
- If the stains are too deeply ingrained and cannot be removed, they can be painted over with whitewash or special dyes.
In addition to stains, defects also include holes and, naturally, they must be repaired before facing with any materials. To do this, the hole is shaped into a rectangle, cleaned of dust and covered with a solution.
Any surface on which restoration is carried out must first be cleaned in separate places from dirt and dust. After this, it must be treated with a soda solution.
If you decide to restore the wall under the tiles, then:
- first, the entire tile is tapped with care and its poorly secured parts are immediately removed;
- sometimes the tiles are not removed simple method tapping, then you have to break it in separate places. This must be done very carefully, starting from the middle and slowly moving to the edges, so as not to damage the adjacent tile;
- if a fairly strong layer of old mortar remains in place of the tile, then it is better not to touch it. You can stick it on it new tiles using special glue, as shown in the photo. This glue is based on casein-cement mastic and is added to the solution in a certain proportion - 1 to 3 to 1 to 2.5. Where glue and sand occupy one part each, cement accounts for three parts, and water accounts for two and a half. At the connection to the window, double-sided foam tape is used under a layer of plaster.
Cracks
A wall with cracks is cleaned of residues facing materials and covered with a layer of primer. After a few hours, when the primer has completely dried, the surface is cleaned to perfect smoothness.
We mix the cement mortar and apply it in a thin layer to the surface, after which it is leveled using the rule, as shown in the video. If the crack is very large or there are many of them, then you can resort to plaster mesh. It will give strength to the plaster layer.
Alignment
Wall alignment can be achieved in three ways:
- using special panels for finishing;
- applying a layer of plaster;
- by combining.
Drywall can also be used for leveling. Most perfect option for any surface is the use of plaster and drywall at the same time.
By hanging a wall, you can find out how much it deviates from the norm. To do this, hammer a nail at a distance of 30 cm from the ceiling. A plumb line is attached to it and a second nail is driven in from below. The same thing is done on the other side. Cords are stretched between the nails from the upper right nail to the lower left. The cords are pulled similarly between the second pair of nails. If the distance between the wall and the cord is more than 5 mm, then the surface must be leveled.
Let's sum it up
Before any cosmetic work, old plaster must be checked. Its restoration will not take you much time and effort, but will save you from completely redoing the renovation and unnecessary financial costs.