Plastering Concrete Walls – Detailed Complete Instructions

The process of plastering concrete walls can turn an unfinished, bare surface into a smooth, long-lasting, and aesthetically pleasing finish. Being able to plaster a concrete wall correctly is a useful skill whether you’re building a new project or remodeling an old one. Even those who are unfamiliar with do-it-yourself home renovations can complete the task if they have the necessary patience and tools.

Preparation and meticulous attention to detail are essential for a successful plastering job. It’s crucial to prepare the concrete wall’s surface before applying plaster. In order to prevent dust, grease, and other loose particles from interfering with the bonding process, the wall must be thoroughly cleaned. A smoother finish and improved plaster adhesion are the outcomes of properly priming the wall.

When the wall is ready, plaster application is a sequence of steps that include mixing the proper consistency, applying the "scratch coat," which is the first coat, and then applying one or more finishing coats. Applying each layer carefully and allowing adequate time for drying in between coats is necessary. A surface that is resilient and even can be prepared for painting or other decorative finishes with the appropriate technique.

We’ll walk you through every step of the procedure in this guide, providing thorough instructions on how to plaster a concrete wall at each stage. These steps will help you achieve professional-looking results that will hold up over time, whether your goal is a perfectly smooth finish or a textured look.

Rough, unfinished walls can be smoothed into long-lasting, aesthetically pleasing finishes with plastering. From surface preparation to the final coat, this article offers detailed instructions that will walk you through the process with simple to understand advice. This guide will assist you in achieving professional-looking results, ensuring that your concrete walls are both functional and aesthetically pleasing, regardless of your level of experience with plastering.

Is It Necessary to Plaster Concrete Walls

Most frequently used in construction, concrete is a very strong, long-lasting material. Concrete walls are not good for painting or wallpapering because their surfaces are not smooth. Plaster is the best material to finish concrete, level it, and smooth out any irregularities.

This substance is strong enough to form a smooth, monolithic coating.

Plaster finishing benefits include:

• versatility;
• easiness to lay;
• the possibility of additional insulation, sound insulation;
• it is possible to create various textures or structures;
• a wide selection of materials (both in price and in other parameters);
• repairability;
• environmental friendliness, etc.

Concrete walls are rendered impervious to moisture, impact, mold, efflorescence, ultraviolet light, and other detrimental elements through the application of plaster.

Decorative mixtures can be used for finish plastering, adding uniqueness to the exterior or interior that reflects the owner’s aesthetic preferences. It’s time to discuss them since using the correct plastering materials and adhering to technology ensures long life for plastered structures.

How to plaster concrete walls

The term "plaster" in general conceals a wide range of materials. Plaster compositions are typically categorized based on the type of base, application location, extra functions, etc.d. to facilitate navigating this diversity.

With respect to a concrete base, by intention:

• conventional (used for rough leveling of concrete walls, sealing holes, cracks, joints, cracks);
• decorative;
• special (X-ray protective, noise reducing, sanitizing, etc.).).

Application locations: internal, external, and facade.

Not all plaster mixes are appropriate for plastering because concrete can vary; gas and foam concrete structures, for instance, are frequently found in private homes. You must familiarize yourself with the primary composition types in order to answer the question of what to use for plastering concrete structures.

Cement-sand mixture

Cement-sand mixture (CSM) is the plaster of choice for concrete used outdoors most of the time. When the mixture solidifies, cement serves as a binder to create an artificial stone with high strength and frost resistance. While sand filler allows you to drastically cut down on the amount of cement needed, it does not weaken the stone. The workability of the mixture and the texture of the cement coating are influenced by the size of the sand grains.

Additives are added to the cement mixture in addition to these two elements, providing the solution with the necessary properties. They are employed to improve the solution’s plasticity, water and frost resistance, as well as other working mixture and finishing coating parameters. Certain coatings use white cement.

• strength (depends on the brand of cement used, the ratio of components);
• durability;
• frost resistance;
• waterproof;
• versatility (used outdoors and in various types of premises);
• ease of preparation and application of the solution;
• maintainability;
• availability, low price of components;
• manual or mechanical application possible;
• fire resistance;
• good adhesion.

The cement composition is unsuitable for use in homes near railroad lines and in seismically active areas. Building shrinkage and vibration loads are too much for mineral plasters to handle. Thus, it makes more sense to select mixtures based on polymer bases for newly constructed buildings.

Due to their high dead weight, DSPs are not appropriate for plastering foam concrete blocks, cellular concrete, or aerated concrete. However, this mixture works particularly well for plastering concrete walls in one-story homes.

For plaster, sand and cement are frequently mixed separately. This brings down the cost of plastering work considerably. The main component proportions are determined by the cement grade, the coating design grade, and the presence or absence of additional binders in the plaster mixture.

The form of cement plaster that is sold is a dry mix that is kept in kraft bags (henceforth referred to as SS). Both cement powder and SS have a one-year shelf life.

Gypsum plaster

Because of the "hydrophobia" associated with the gypsum base, interior work typically uses gypsum plasters, though there are occasional exceptions. It’s the leader right here.

The primary benefits of gypsum mixtures that they "boast" about are:

• fast strength gain;
• low coating weight;
• vapor permeability;
• environmental friendliness;
• ease of forming a smooth surface;
• versatility (in relation to the base material);
• ease of repair;
• easy formation when creating relief surfaces;
• non-shrinkage of the mixture during hardening;
• fire safety;
• water retention (the solution does not release moisture to porous substrates);
• low thermal conductivity;
• high adhesion.

One drawback of gypsum coatings is

• rather low frost resistance;
• setting too quickly;
• instability to biological damage.

Prominent producers of plaster mixtures have mastered the art of handling nearly all of gypsum’s drawbacks.

Other options for plastering materials

For finishing concrete bases, in addition to the materials listed above, compositions of gypsum-lime, acrylic, polymer-cement, lime, silicate, and polymer are used. Their characteristics, costs, and potential for use with the base material vary. For instance, silicate compositions work well as a plaster for street-side cellular concrete. Acrylic mixtures are not used for leveling because they are applied in a thin layer.

Preparing the walls

The concrete surfaces must be prepared before plastering in order for the plaster to adhere tenaciously, meet technical specifications, not develop visible rust or efflorescence patches, and last for a long time. That is, before applying the mixture, the surface needs to be dry, clean, and rough. Furthermore, there shouldn’t be any big cavities, fractures, or excessive metal inclusions.

1. Remove the unusable old coating (whitewash, wallpaper, peeling plaster layers, paint);
2. Cut off protrusions and concrete drips. Plane off protrusions of cellular concrete. To repair chips, cracks, and cavities, use cement-sand mortar with proportions of 1:3. In case of large defects, “patches” are made with reinforcement.
3. A smooth concrete surface is “dotted” with notches to improve adhesion.
4. Remove excess metal elements, otherwise, having rusted, they will cause rusty streaks to appear on the finishing surface. The remaining metal objects are insulated using oil paint.
5. The surface is cleaned of stains of various origins (foci of mold, grease, efflorescence, rust).
6. Dust is swept or washed off the walls.
7. The clean surface is primed, then dried.
8. If the thickness of the plaster layer is ≥7 mm, beacons are installed.
9. If the leveling coating is thick, a reinforcing mesh is attached to the concrete.

When preparing the walls, grooves are made if concealed internal wiring is available.

How to plaster concrete walls

In particular, novices are curious about how to plaster a concrete wall using their hands. As a result, we have included videos and thorough instructions for carrying out each task below.

The following technologies are used to plaster concrete structures:

1. Surface preparation in accordance with regulations.
2. Impregnation (application) of the primer composition.
3. Drying.
4. Installation of the reinforcing mesh (if provided).
5. Application of tile adhesive as a future base
6. Installation of beacon strips.
7. Preparation of the solution.
8. Performing a splash coat.
9. Mixing the mixture, performing a primer.
10. Preparing the mixture for the top coat, applying the top coat.
11. Performing a grout.

Priming

Applying the plaster mixture to a porous base will cause the wall’s surface pores and microcracks to instantly start absorbing water from the solution. The dehydrated composition won’t have enough water for the reactions to happen when it hardens. Consequently, no robust, long-lasting coating forms.

A primer, which coats the base’s surface with specific compounds, is used to stop the base’s pores from "robbing" the solution. The reliable adhesion of the coating to the base material is the second reason to use a primer. Antifungal protection is one of primer compounds’ key functions.

Concrete-specific compounds are the best choice when priming a concrete wall. These consist of cement, acrylic additives, and quartz sand in concrete contacts.

Deeply penetrating the base’s pores and microcracks, the composition forms a robust waterproof layer and offers dependable adhesion to other compositions as well as cement plaster. Under typical circumstances, concrete contact dries in 2.5–3 hours.

Aerated concrete constructions are primed using "Gazobeton-kontakt" and "Starateli" compositions. Three primes are applied to facades. twice in the interior walls.

Twice the concrete surface is primed, with a drying interval in between. A wide brush is used to apply the composition, and a roller is also used to achieve an even coating. The grooves are filled with electrical wiring once the final coat of primer has dried completely.

Installation of beacons

It is not necessary, but not every professional can plaster concrete walls evenly without the use of beacons. Plastering can be completed much more quickly and smoothly when beacons are used. A smooth surface can be created nearly every time. Attached to the base are guide strips known as beacons. The strips can be made of wood, plastic, metal, or plaster mortar (gypsum).

On the surface, beacons are placed with a step of between one and three meters (some plasterers use a larger step – up to 1.7-1.8 m). This is carried out following the measurement of the wall’s curvature to determine its most projecting point. Use a plumb line, cords, and a level (a laser level is the most convenient tool for this task) to install beacon strips. The extreme (base) beacons on the wall are about 30 cm away from the corner.

The walls may "fall" inward or outward, or they may have an uneven, bumpy surface. The angles between the walls (measured with a rectangular plate or a large slatted square) might not be exactly right. Installing beacons at the point where the first (extreme) strips are displayed may be simpler or more challenging, depending on this.

With the aid of tension cords or a laser level, you can locate the wall’s most prominent point. The outer beacons are set in accordance with it (considering the minimum thickness of the plaster layer). Then all the intermediate beacons are set, with an emphasis on the outer ones.

How to properly make beacons out of gypsum mortar in a video.

Applying tile adhesive

Typically, new building materials aren’t just utilized where they were meant to be. Tests were conducted on tile adhesives for wall leveling. The adhesive mass is plastic, sticky, dries fast enough, and strengthens, so the results are satisfactory. The adhesive composition can be used to connect entirely different materials and is a good transition agent.

Utilizing a trowel or spatula, the mixture is applied. Using a trowel with a notch, the layer is "combed" after application. The following materials—plaster or putty—are securely held on the adhesive because of the grooves.

Reinforcement

An adhesive composition is also utilized for reinforcement during finishing. First, the composition is applied in a 5–10 mm layer. Using a spatula to smooth the surface, the web of the reinforcing mesh is sunk into the adhesive mass after it has been applied on top of the solution. With a notched trowel, the solution’s protruding mass is "lined." It has dried on the layer.

The corners are strengthened by the use of perforated corners. They are pressed into place onto a thin layer of plaster composition or adhesive, and then another layer of solution is applied on top.

First layer of splash

Concrete wall plaster needs to be leveled in multiple layers. The purpose of the first (splash – up to 5 mm) is to guarantee adherence to the main layer’s concrete surface. The viscosity of the solution is reduced. Using a trowel or ladle, toss it onto the wall. The solution adheres to the wall as it slaps against it.

There is not a level surface. A horizontally oriented spatula corner is used to line the splash surface in order to enhance adhesion to the next primer. Once the spray application is finished, move on to the primer application. The next layer is applied the following day if this cannot be completed before the spray grabs.

The soil is the main layer

Make a viscous solution for the soil. applied using a trowel or spatula, hurling it above the lighthouses’ summits. The site complies with the rule when the solution is filled in the space between the beacons, which is about a meter long. In order to do this, the rule is applied to the wall while it is supported by beacons and is moved in a zigzag pattern starting at the bottom.

Simultaneously, surplus solutions are gathered on the rule and disposed of in a container or added to areas that lack sufficient solution. The tool is pointing in the opposite direction after applying the rule from the bottom up two or three times. As a result, the solution’s position on the wall is stable.

Putting a mixture over one area, then the other. Plaster for concrete walls is applied in layers if a substantial leveling layer thickness is needed. Using a spatula, gently level the lower layers.

With the exception of the mortar-based ones, the beacon strips are taken off once the upper leveled layer hardens. Using a spatula, the resulting grooves are leveled and the plaster mixture is added. The cover layer, or third layer, is not made if decorative plaster is to be used for the final finishing.

If the final coating is thin-layer, additional surface preparation for plastering with decorative compounds consists of priming and puttying, or just priming (if the final structural coating is capable of hiding small defects).

Face layer cover

The surface of the coating must be exceptionally high quality for painting or wallpapering. Unevenness and large pores are prohibited. A cover layer, the third layer of plaster, is applied for leveling. A finer (up to 1.5 mm) fraction of sand is combined with a solution of a more liquid consistency. Using a wide spatula, apply the solution in a layer as thick as 2 mm to the base that has been moistened.

Grout

The surface is rubbed when the cover becomes slightly sticky and gives way when lightly pressed with the finger. There are three stages to the grater operation. Circular grout is the first. executed with light pressure on the surface and circular motions. The pressure is higher over bulges and lower over depressions. Milk that clogs the grater’s edges is poured into a container. Applying a small amount of coating solution can help if the depressions are too big. Occasionally mist the exterior of the wall with water.

Smoothing, or grouting, is the second step. There is a straight line movement of the grater up and down. carried out with hardly any pressure and without taking the tool off the surface.

Features and differences of external and internal work

When using façade plaster, different operating conditions apply than when using interior finishing. Also different are the finishing work conditions.

The following circumstances are typical:

• temperature below +30°C, above +5°C;
• air humidity – up to 60%;
• electrical wiring of the wall is de-energized;
• try to protect from curious children and animals.

Concrete wall plastering on facades is done during dry weather. Provide shelter from intense winds and rain, as well as shade from the sun and rain.

Avoid making heavy drafts on the property. Avoid using fans or heaters to dry the walls.

Step	Description
1. Surface Preparation	Clean the concrete wall to remove dust, dirt, and loose particles. Apply a bonding agent to ensure good adhesion between the wall and plaster.
2. Mix the Plaster	Prepare the plaster mix according to the manufacturer"s instructions. The mixture should be smooth and free of lumps.
3. Apply the First Coat	Using a trowel, apply the first coat of plaster, called the scratch coat, evenly over the wall. This layer should be rough to help the next coat adhere.
4. Let It Set	Allow the scratch coat to set but not fully dry. This usually takes a few hours.
5. Apply the Second Coat	Apply the second coat, known as the brown coat, over the scratch coat. Smooth it out with a trowel and make sure it is even.
6. Finishing Touches	Once the brown coat has set, apply the final thin coat, also called the finish coat. This coat should be smooth and ready for painting or other finishing.
7. Let It Cure	Allow the plaster to cure completely, which may take several days. Keep the area moist to prevent cracking.

Although plastering concrete walls may seem like a difficult undertaking, it is completely manageable with the appropriate planning and equipment. It’s important to take your time and prepare your surface correctly. After cleaning and caulking any cracks, use a bonding agent if necessary. Plaster will adhere well and last for years if these steps are followed.

Patience and practice are key when it comes to plaster application. Don’t rush the process; instead, apply the plaster in thin, even layers. It’s critical to allow each layer to completely dry before applying the next. This will give you a smooth, long-lasting finish and stop cracking.

Don’t forget to add the final touches. A professional appearance can be achieved by smoothing the surface and letting it completely dry before painting or decorating. Your room can be completely transformed by plastering concrete walls, which also give your walls more style and protection.

Video on the topic

Preparing concrete walls for plastering. Grinding concrete. #grindingconcrete #plaster #vlg #vlz

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