Wet plaster: step-by-step technology for insulating a facade

One common technique for finishing and insulating building facades is wet plastering. This method enhances a building’s aesthetics in addition to increasing its energy efficiency. You can minimize heat loss and shield the structure from inclement weather by adding several layers of insulation and plaster.

This strategy works especially well for commercial and residential properties. It offers a strong, long-lasting finish that withstands weather, wind, and sun exposure admirably. It also provides versatility in terms of decorating options, supporting a variety of colors and textures.

From the initial surface preparation to the last plaster coat, there are numerous crucial steps in the process. A high-quality, long-lasting outcome requires using the right materials and following the right procedure. We’ll dissect the exact process of applying wet plaster to insulate a facade in this guide.

Plaster, reinforcement, and insulation layers are all combined in wet plaster, a tried-and-true technique for insulating facades to produce a long-lasting and energy-efficient exterior. Applying insulation boards, encasing a reinforcing mesh in a base coat, and adding a decorative plaster layer are the steps in the process. This methodical procedure protects the building from weather damage and enhances its appearance in addition to improving thermal performance.

What is a wet facade

There are three methods for warming walls:

• increase the thickness of the walls themselves;
• attach a layer of insulation to the facade, covering it with waterproof sheet material (with the arrangement of a ventilation gap) – ventilated facade;
• attach a layer of insulation by plastering the surface – non-ventilated facade.

Compared to the additional material needed to increase the wall’s thickness, insulation is far less expensive. Modern insulation materials, however, are readily harmed by even small amounts of mechanical stress. They won’t survive for very long without protection. Mineral wool loses heat when it gets wet. Birds enjoy pecking at polystyrene foam, and wasps and bees create their own nests by gnawing through gaps. Severe hail can easily cause ulcerations on any insulation’s surface, which can impact the coating’s ability to retain heat as well as the house’s aesthetic.

It was someone’s deft touch that gave rise to the term "wet" facade, also known as wet plaster, for an unventilated facade. Maybe this is because plaster solutions that have been diluted with water were used. The technology first surfaced in Germany over fifty years ago.

It is possible to install sheet insulation indoors as well as outdoors. Although doing the second is simpler, it should only be done in cases where external insulation is not feasible.

When covering the facade with insulation:

1. The insulation layer reduces the interior space of the rooms.
2. The dew point is carried out beyond the room and the thickness of the walls, located in the insulation layer.
3. The rooms cool down more slowly, as the effect of heat accumulation occurs.
4. Cold bridges do not form in the wall.

What layers does a wet facade consist of

When mineral wool, polystyrene foam, or foam plastic are used as building materials for wall insulation, a multi-layer coating comprising various building materials is produced using wet facade technology.

Every layer carries out a specific task.

1. The base is a wall structure, which can be made of brick, reinforced concrete, OSB or other material. The surface of the base must be smooth so that air circulation does not occur under the insulation layer. Free movement of air sharply reduces the heat-retaining properties of the complex insulation system.
2. One or two layers of primer (antibacterial, fire-resistant, increasing adhesion, etc.). d.).
3. Plaster-adhesive mass, through which insulation sheets are glued.
4. Layer of thermal insulation material. The layer thickness is designed based on heat engineering calculations. The method of performing and fixing the layer to the wall depends on the type of insulation.
5. Adhesive plaster composition, in the thickness of which there is a reinforcing mesh (creates a shell that resists mechanical impacts).
6. A layer of leveling plaster.
7. A layer of primer.
8. Finish coating (paint or decorative plaster) – an aesthetic function.

Wet facade installation technology

When the outside temperature is +5 o C or higher, wet plastering can be done.

Numerous producers offer wet facade systems. It is recommended to utilize them entirely, avoiding substituting materials from one manufacturer with those from another.

The following workflow is enabled by the technology:

• hanging the facade;
• preparing the base;
• priming the facade surface;
• installation of the base profile;
• installation of insulation;
• installation of a reinforced base layer;
• priming;
• finishing.

Taking measurements

To check the geometric parameters of the facade plane before starting work, the facade is hung using cords. This work is carried out in the same way as the process of installing beacons. To do this, we drive a piece of reinforcement with a diameter of 12-14 mm into the upper corner of the wall. We tie a nylon cord with a plumb line to it at a distance of L (5-10 mm + insulation thickness) from the wall. We drive in a second piece of reinforcement along the line of the cord, to which we tie the cord (with some tension). We get a strictly vertical cord. We stretch the second vertical cord in a similar way on the other side of the wall. We attach a horizontal cord to these cords using paper clips, which can be moved vertically.

We utilize the vertical auxiliary plane defined by these cords to calculate the façade surface. We measure the distances between the movable cord and the wall surface at different points along the facade. The measurement results are noted in a notebook. We create a schematic map of deviations using this data. In this manner, we can determine which parts of the facade are the most prominent and assess the extent of any collapse.

An extra vertical cord is inserted in the space between two vertical cords if the walls are very long. The measurement procedure will then be unaffected by the wind.

We determine whether to increase the insulation layer’s thickness and whether it is acceptable to keep the wall’s angle of inclination (if we use sheet insulation of the same thickness) based on the hanging results and the nature of the deviations. If the wall’s geometry needs to be adjusted, thicker sheets can be used, and a cutter can be used to cut the sheets’ surface at the appropriate angle. It is also possible to trim off individual wall protrusions. However, using plaster mortar to level the wall beneath the facade’s wet plaster is not advised.

Preparing the wall for application

Of course, wet plaster on the facade will hide any wall flaws, but if the flaws are left unfixed, the result could be a very shoddy coating. In this instance, a smooth, superior coating will be impossible to achieve or the layer of wet plaster may simply slip off the base. As a result, a visual and tactile inspection of the base is conducted.

Drips of plaster or concrete mortar are knocked down. A wall composed of blocks has its seams examined. If there are any cracks, they are sealed with adhesive mass, foam glue (such as ST-84), or mortar. The portions of the masonry mesh that protrude are chopped off if they do. There is concealed electrical wiring in a groove.

In the event that the facade is plastered, the tapping-identified detached areas are cleaned, and mortar is used to fix the coating. In order to fix large cracks, reinforcing mesh is applied.

The strength of paint adhesion to leveling plaster is tested on a painted facade. Any weak putty layer beneath the paint is eliminated entirely.

Prior to beginning work, sturdy, stable, and comfortable scaffolding must be installed. In newly constructed buildings, all window and door units have to be installed by the time the insulation is put in. The facade surface needs to be cleared of debris, dust, rust, efflorescence, and fungal growths before priming. Masking tape and film must also be applied to the frames, glass, and platbands.

Primer

For wet plaster to work, the plaster-adhesive mixture must be able to reach the manufacturer’s stated strength. In order to accomplish this, a primer must be added to keep the mixture from drying out. Primers are applied to the base in order to seal the wall materials’ pores. If not, the walls will absorb the moisture required for the chemical reactions that lead to curing once the glue is applied. Along the way, the primer will adhere the last bits of dust to the wall material and reinforce its surface layer. As a result, the circumstances will be established for the solution and the wall to establish a trustworthy connection.

Experts in wet insulation systems advise priming in three stages. Every step of the priming process calls for a different composition. We use the primer CT17 as an example, which is diluted with water prior to use.

1. For the first layer, we dilute the product in a ratio of 1:6 (for 6 parts of water, we take 1 part of the primer concentrate). Priming is carried out using a garden sprayer, watering the surface heartily. Our task is to saturate the base as much as it can accept. Therefore, we spray the primer intensively so that it almost runs along the surface. A significantly diluted product is less viscous and is able to penetrate very deeply into porous materials. After spraying, wait until dry spots begin to appear on the drying surface. When they cover more than half the surface area, move on to the second pass.
2. We carry out a similar procedure (with all the nuances) with a solution diluted in a ratio of 1:4.
3. We perform the final pass more carefully. We do not need to pour so much primer, otherwise a glossy film will form, which will reduce adhesion. Dilute the product in a ratio of 1:2.

Let the primer that was applied dry. As soon as the primer is sprayed, remove the protective film and adhesive tape.

Installation of the base profile

Install a base metal profile to shield the bottom of the "layer cake"’sinsulatinglayer from knocks and abrasions. The profile should be positioned 40–60 cm above the ground. During installation, the profile also helps to support and align the bottom row’s insulation sheets. Using a laser level, precisely align the metal profile horizontally.

The U-shaped profile is modified to fit the shelf’s measurements in accordance with the insulation’s thickness. There should be no spaces between the sheets and the profile. There is no overlap when creating the joints. The profiles of the neighboring walls are cut at the locations where the insulation changes to the adjacent wall, ending in a 45-degree angle.

Drill holes in the wall for the dowels in order to install and secure the base profile. There are at least three holes for every linear meter of the profile.

After leaning the profile up against the wall, we hammer plastic dowels into the holes. Polyethylene lining washers are occasionally used to line the space between the wall and the profile.

We cut the profile at a 45° angle if it extends above the nearby base. Polystyrene foam boards should overlap the end of the board by at least 200 mm from the lower mark of the first floor and basement overlap in homes with basements and technical underground.

The base profile in the installed form should be positioned in a single line with no overlaps or component deformation at the joints.

These articles on the subject might also be of interest to you:

1. Plastering the base.
2. Plastering the basement.

Insulation board installation

First, as directed by the instructions, prepare the adhesive composition. Pour the dry mixture into a container with water gradually, and use a mixer to stir. For five minutes, we operate at a low speed; during this time, no lumps remain intact. Stir for an additional five minutes after pausing for six minutes.

Since the solution doesn’t last long, it makes more sense to mix it gradually rather than trying to rejuvenate it once it has begun to set. Remixing is advised in the event of a 10- to 15-minute work break. The strength of the adhesive composition determines how well the insulation adheres to the wall and, consequently, how well the wet plaster adheres to the wall as a whole.

Two methods are used to apply the glue to the sheets:

• in strips along the perimeter with 1-3 heaps in the center;
• continuous spreading.

In the first option, a 10-cm-wide strip is applied with a 2- to 3-cm-deep indent from the sheet’s edge. The applied solution has a height of between 10 and 20 mm, depending on how even the wall is and how difficult it is to ensure that adjacent sheets form a flat surface. 3–5 circular cakes that are about 20 cm in diameter are placed in the middle of the sheet.

The sheet can be completely covered with adhesive if the surface is level. Use a notched spatula with teeth that are 12 mm tall for this purpose.

The adhesive composition application has unique properties. Initially, apply a small amount of glue to the plate (under the straps as well as along the strip line) by rubbing it in with force. The remaining amount is applied only after this.

Please take note that there is no adhesive mass covering the empty areas on the outer sheets that will extend past the wall. The slab is marked before the adhesive composition is applied, with an indentation of two to three centimeters made from the drawn line.

The slab covered in glue is pressed firmly up against the wall. To get an even distribution of glue between the wall and the slab, move the object slightly (along the wall while pressing) and then move it back to its original position. Using a spatula, remove any excess adhesive mass that has emerged right away. In areas where the solution has not come out, it is carefully smeared in from the side and pushed between the wall and the slab using a spatula. The possibility of any air movement beneath the insulation layer must be completely eliminated.

Row by row, insulation is installed along the wall starting from the corner. Slabs are installed as closely to one another as possible when they are joined. Should a gap arise due to any reason, it is filled using wedges or strips that have been cut from the insulation. Such seam sealing is unacceptable because it produces cold bridges when adhesive mass is used to fill the gaps.

Fundamental guidelines for dressing sheets:

1. Vertical seams of adjacent rows must be offset by at least 200 mm.
2. When installing the slabs of the first row, the surface of the insulation must closely approach the front wall of the profile.
3. At the corners, the protruding slabs of adjacent walls should form a lock (also with bandaging).
4. Window and door slopes are insulated with thinner slabs, which are made to protrude by the thickness of the wall insulation. The junction of the slope insulation and the wall must be tight.
5. If a short sheet is installed on the corner of the facade, its width must be at least 20 cm.
6. Vertical or horizontal seams of the wall insulation must not coincide with the edges of the slopes. If such a situation occurs, then L-shaped inserts (G-shaped inserts) are made at the corners, the length of the shoulders of which is at least 200 mm.

The adhered sheets continue to move for a while (until the adhesive solidifies). In this period, the plane of the generated surface is controlled and corrected using a rule. A wide wooden block or a rule is used to press down on any sheets that protrude or the corners of the sheets.

The sheets are further fastened with mushroom dowels after three days, or until the adhesive mass hardens. Each insulation sheet needs to be fastened at five different locations (the corners and center). One mushroom is frequently used to secure the corners of subsequent sheets together.

Using a hammer drill, a hole is drilled through the insulation for the dowel. The depth limiter is then adjusted to the required length of the dowel, plus an additional 15 mm.

Use caution when installing plate dowels for walls composed of various materials. They can be driven in or screwed in. The length is the same as the insulation’s thickness plus an additional 6 cm for wall fixing.

A metal spacer core is used to secure the mushroom after it has been placed into the hole. It is imperative that the cap be set back into the insulation sheet by about 1 mm. It is still there to keep the plaster mortar away from the metal of the core cap. In the event that the utilized cores lack a thermal cap, polyurethane foam puttying will suffice.

Application of the base reinforced plaster layer

The actual wet plastering is then carried out. Either the same plaster solution or one with a different composition is used to create the "shell." The combination selected has no bearing on the application technology itself.

We start by processing the areas that are the hardest, like corners and slopes. We prepare the corners for plastering by cutting mesh shelves to the appropriate length and combining the solution.

1. Apply a 20 cm wide strip of mortar along the corner on both sides with a spatula. To make it easier to fix the applied mesh, we go over the strip with a notched trowel (the height of the teeth is 5 mm).
2. Install the corner along the corner line, align the mesh.
3. Leading along the mesh with a regular spatula, press it into the layer of mortar (not allowing it to be pressed to the surface of the insulation). In this case, the mortar mass appears through the mesh cells and is spread with a spatula over the threads. We make sure that there are no sections of the mesh not covered with mortar.

The insulation layer should cover the window or door frame on slopes. However, no glue is applied to the side of the insulation that comes into contact with the frame during installation. After installation, foam is used to fill the space. Slopes are insulated by marking and carefully cutting out insulation sheets. mounted similarly to wall slabs by smearing glue.

The insulation beneath the window will be covered by a window sill. As a result, the insulation is removed at the appropriate angle from the top.

We strengthen the wall’s remaining surface after addressing the trouble spots:

• apply the plaster composition;
• line it with a notched trowel;
• apply and straighten the mesh;
• press the mesh into the solution, running the trowel over it.

We overlap the mesh panels by 10 cm when joining them. The mesh "shell" cannot have any gaps in it. The base profile’s bottom is where the mesh’s bottom is cut. Once the glue has solidified, a properly positioned mesh will separate from the foam plastic.

Rectangular mesh gussets provide additional reinforcement to the tops of the slope corners. They are positioned across the angle’s hypotenuse, atop the corner’s side meshes.

The adhesive layer is rubbed off after it hardens. Another layer of leveling plaster up to 2-3 mm is applied if additional finishing, such as decorative plastering or tile cladding, is not planned. The layer is removed with caution.

Decorative finishing

When doing decorative work, they start the finishing process after letting the facade’s wet plaster dry. Two applications of a product matching the plaster mixture (laid and decorative) are made to prime the surface. This is typically a primer for water dispersion. See the Decorative Plaster section for information on how decorative plastering is done. For this, it is advised to use plaster varieties with high vapor permeability, such as silicate.

Advantages and disadvantages of wet plaster on the facade

The following are some benefits of wet plaster over ventilated facades:

• no need to install a complex frame;
• since the insulation layer does not include a frame, cold bridges are not formed;
• the coating is lightweight;
• if the thickness of the insulation is chosen correctly, the dew point is located outside the wall body, the wall remains dry, conditions for the settlement of fungus and mold are not created;
• the coating serves as a good noise-reducing barrier;
• the simplicity of the technology allows beginners to make a layered facade with their own hands;
• the coating is easily updated by painting or re-grinding the plaster;
• long service life;
• the outer layer has good resistance to external loads.

Among the drawbacks are:

• the need to use high-quality materials and precise execution of the technology;
• seasonality of execution.

Required tool

The tool is prepared ahead of time to make working with it more convenient and straightforward. There will be a variety of tasks to complete, not just plastering, so a varied toolkit is required.

• Electric drill (screwdriver);
• punch (prepare the nozzle for the installation of dowels);
• construction mixer;
• Cut for profile cutting.

Hand instruments and apparatus:

• Spatulas with a width of the shoulder blade 350 and 80-100 mm;
• Kelma gear made of stainless steel with teeth 8-10 mm;
• hammer;
• construction level;
• Glade;
• a heifer equipped with a sandpaper or an abrasive mesh;
• roller, wide brush (for priming);
• half a month;
• a heap for the formation of a decorative structure (300-400 mm long);
• Construction knife for cutting canvases of the reinforcing mesh;
• a container for an adhesive mixture;
• Maslar adhesive tape;
• nylon cord;
• Pure rags.

A homemade tool for thinning sheets of polystyrene foam leaf will be helpful for users of that material. Sample wooden rack-based ray saw (also called the "goat"). The first nichrome thread is employed as a cutting "blade." diameter of 0 mm (allowable range: 0.8-1.2 mm). The transformer supplies voltage at 220/24 V and has a capacity of 250 (up to 400) W.

How to choose insulation

The choice of insulation material for wet plastering of the facade is primarily determined by its capacity to both retain heat and "breathe." Consequently, facades without forced ventilation do not use EPSP. There are two choices among the materials that are still available:

• PSB-S 25F (polystyrene for facades);
• Mineral wool slab (MWP) specially developed for the wet facade system.

MVP has a density of about 130–150 kg/m3 and can be used to insulate bases composed of brick, aerated concrete, or any other material; however, there is a requirement that the upper layers of the wet "pie" have a high vapor permeability. Paints and ornamental plasters made of acrylic cannot be boasted about. For the same reason, mineral wool finishing cladding cannot be completed with artificial or natural stone clinker tiles. As a result, it is advised to stay away from the materials mentioned. In the shape of a continuous coating, anyway. It is acceptable to decorate with individual tiles.

The density of expanded polystyrene meant for facades is 16–18 kg/m3. Benefits of it:

• higher water resistance than MVP;
• more durable;
• slabs are simpler and easier to work with;

However, it is required to account for moisture accumulation in the wall if expanded polystyrene is chosen for finishing structures composed of highly porous materials, such as aerated concrete, polystyrene concrete, expanded clay concrete, and the like.

Expanded polystyrene coatings on public buildings are required by fire safety regulations to be cut with non-combustible lintels to prevent the spread of fire from apartment to apartment along the facade. The interior of a private residence is where fires typically spread. A layer of mineral basalt wool, equal in thickness to the cotton wool slab, is used to make such cutting lintels.

When selecting insulation, these characteristics are taken into consideration.

Articles that could be helpful to you about plastering various kinds of insulation: foam plastic and penoplex

Step	Description
1. Surface Preparation	Clean the facade from dirt, dust, and old coatings. Repair any cracks or damage.
2. Primer Application	Apply a deep-penetrating primer to ensure better adhesion of the plaster.
3. Insulation Installation	Attach insulation boards (like mineral wool or polystyrene) to the facade using adhesive and dowels.
4. Reinforcement Layer	Apply a base coat of plaster with embedded fiberglass mesh for strength.
5. Decorative Plaster Application	Apply the finishing layer of plaster, choosing the desired texture and color.

The energy efficiency and weather protection of your home can be greatly improved by properly applying wet plaster for facade insulation. You can get long-lasting results by carefully following every step, from prepping the surface to applying multiple layers.

An insulated facade that is both long-lasting and efficient requires careful selection of materials and adherence to suggested installation methods. When choosing your plaster and insulation, take into account the unique characteristics of your wall type and local climate.

The benefits of a well-insulated and attractive facade make the process worthwhile even though it may seem time-consuming. Your property can have better curb appeal and thermal performance with careful planning and execution.

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