House plastering technology wet facade

Recommendation points

• Insulation system
• Base reinforcement layer
• Alignment
• Decorative plaster
• Coloration

The wet facade technology continues to be actively used in civil engineering, despite the complexity of the work and the high cost of quality materials. We will tell you how to properly decorate facades in this way, and what pitfalls may arise.

Insulation system

The complex technology of plaster facades implies external wall insulation with plates of extruded polystyrene and similar materials with high density. In addition to the function of thermal protection, the insulation slabs provide high-quality leveling of the walls even with their significant initial curvature and deviation from the correct geometry.

The insulation must be fixed mechanically and by means of special glue. Disc dowels are used in the amount of 5–7 pieces for each plate in order to immobilize it during the glue setting and subsequently to strengthen the quality of fastening. The glue is applied to the seamy side of the insulation with a continuous contour around the perimeter and several lumps in the central part with an average of 30–35 cm indented. Locks on already fixed plates are also abundantly coated with glue, after which the next heat protection element is set in place, tightly pressed against the neighboring and to Wall. Alignment is carried out along the mooring line with a tolerance of about 3-5 mm / m² and 10-15 mm in the common plane. The protruding glue residues are carefully rubbed in the joint area. High-quality fastening of insulation is a guarantee of the durability of the facade finish, this stage must be treated with maximum responsibility.

Along with expanded polystyrene and polyurethane foam, it is allowed to use high-density mineral wool, not forgetting about the increased vapor permeability of the material

In some cases, plastering work is carried out without insulation. When it comes to buildings made of aerated concrete blocks or other walls made by the method of seamless masonry with the formation of smooth walls without local irregularities, facade plaster can be applied without preliminary preparation. If the walls are made of bricks or cinder blocks, a rough alignment is performed before the facade finishing: plastering along the lighthouses with cement-sand mortar of the M50 brand.

Base reinforcement layer

All further stages of plastering should be carried out in compliance with one important rule: compliance with the temperature and humidity regime, which is set by the manufacturer of the used building mixtures. In general, it is considered optimal to perform work in moderately cloudy weather at an air temperature in the shade of 25-28 ° С.

On top of the insulation boards or rough plaster, it is imperative to apply a base layer consisting of a special plaster mixture with a high content of plasticizers and fiberglass reinforcing mesh. This layer is the basis of the facade finish, it is he who provides resistance to peeling and inhibits the formation of cracks.

Initially, the entire surface of the insulation is wiped with glue for expanded polystyrene. The mixture is applied in vertical stripes 1–1.2 m wide with a layer thickness of 1–2 mm. Immediately after application, a facade fiberglass mesh is applied to the glue, which is then carefully ironed with a spatula. After the mesh is recessed, a very thin layer of glue or polymer-cement putty is applied on top, which is carefully rubbed in and leveled with a spatula to cover the reinforcement. In this state, the facade can be preserved for the winter if you cover it with plastic wrap.

Alignment

Before proceeding with the basic alignment procedure, it is necessary to perform a number of preparatory operations. First of all, it is required to install plaster corners at all corners of the building and arrange window and door openings. As a rule, a frame is made for them in the form of pilasters cut from expanded polystyrene, in the same way the architectural design of the facade is made. When all corners have been reinforced, the glue must be allowed to dry completely. When solidified, a film forms on the surface of the glue mixture, which must be cleaned with an abrasive mesh in order to improve adhesion. After cleaning, all surfaces must be dedusted by treating them with one layer of acrylic primer that strengthens the surface, or even better – a contact emulsion diluted with water 1: 1.

To level the walls, a basic cement-based plaster mixture is used with a slight addition of frost resistance modifiers and air-entraining agents (Ceresit CT 35 or similar in composition). It is a fairly crumbly plaster with long pot life and easy leveling. After application, the surface of the mixture remains dry and non-sticky, which makes it easier to control the alignment according to the rule and the line. The thickness of the leveling layer should not exceed 8–10 mm, if more is required, the surface is strengthened with a second layer of reinforcing facade mesh, after which a covering layer 2–3 mm thick is applied. After drying, the plaster must be wiped off with an abrasive mesh and impregnated with a universal acrylic primer.

Decorative plaster

On top of the leveling layer, the facade can be immediately painted, but decorative facade plasters are much more often used, which form a texture on the surface. It can be pebble plaster of the “bark beetle” or “rain” type, fine-textured compositions based on silicone and latex, which, after application, are rolled with a roller, or viscous mixtures rubbed with a flat trowel. The method of preparation and leveling described above allows the use of almost any type of decorative facade plaster.

Since the surface of the walls is finally leveled before decorative finishing, the finishing plaster must be applied as evenly as possible. The best way to do this is to mark the facade with lines into 1 m sections.² and then apply the coating in strictly measured portions according to the application rate. The process of applying plaster itself depends on its type and composition, manufacturers supply their mixtures with detailed instructions, including the description of artistic techniques of work.

Coloration

Painting the facade is required in cases where a layer of decorative plaster was not applied over the leveling base, or if the latter was not painted in bulk. Facade paint has hydrophobic properties, but at the same time it can pass water vapor, it serves as the main element of protecting the facade from weathering.

Before painting, the surface must be thoroughly cleaned of dust and dried, this is especially important if the rough coating has been outdoors for a long time. After cleaning, the facade is coated with a primer paint based on acrylic or alkyd resins, depending on the type of finish paint used. The primer must have time to dry completely before painting..

The best way to apply facade paint is with a velor or woolen roller, depending on the presence of texture on the surface. Since the rough coating is carefully prepared, no preparatory painting is required with diluted paint, you can immediately use a solid one. When painting, the surface of the facade is conventionally divided into sections of 2–3 m², which are painted strictly sequentially with overlapping borders. First, the paint is applied in a continuous layer and rolled in a vertical direction, after which it is necessary to cross-roll with a wet roller. At the final stage, the roller moves diagonally according to the herringbone pattern to eliminate the smallest unpainted dots.