- What is the essence of technology
- What bearing bases are suitable
- Insulation materials
- Protective layer device
- Decorative facade finishing
In regions with mild and temperate climates, there is no need for complex systems that provide absolute protection of the insulation layer. The technology of the “wet” facade is much more economical and simpler in technical terms, today we will talk about the technique of performing the work and the materials used.
What is the essence of technology
A wet facade, in contrast to hinged ventilated systems, does not imply an air outlet for free circulation of street air. Removal of excess moisture occurs due to the natural vapor permeability of the finishing layer. In addition, when choosing materials for insulation, preference is given to thermal insulation that is not sensitive to getting wet during condensation and freezing in this state..
In the classic version, the “cake” of wall insulation looks like this:
- High-density slab insulation is fixed to the carrier layer by means of disc dowels and / or glue.
- The outer plane is leveled by a rough layer of facade plaster reinforced with fiberglass mesh.
- A thin layer of finishing material is applied to a flat and smooth surface.
1 – base; 2 – adhesive layer; 3 – dowel; 4 – insulation; 5 – rough facade plaster; 6 – facade fiberglass mesh; 7 – facade decorative plaster
The main advantages of a wet facade over a ventilated one:
- tangible cost savings;
- ease of work and the absence of strict installation rules;
- low weight of finishing and insulation, self-supporting properties;
- fast application speed;
- the ability to quickly and painlessly build up thermal protection and renew the look;
- relatively free choice of decorative finishes and insulation.
The wet façade is used both in construction and renovation work. This type of finish is considered the most acceptable for the insulation and restoration of the facades of old buildings, including those of architectural value. The technology, among other things, allows you to qualitatively embody (or restore) all kinds of architectural elements, from the simplest moldings to complex bas-reliefs.
What bearing bases are suitable
The main difficulty in the installation of composite facade systems (SFTK) is the competent determination of the correspondence between the type of the supporting base, the insulating material and the method of its fixation. Errors in this regard are fraught with peeling of the finish from the base and its further destruction under the influence of wind loads and other climatic influences..
It is believed that a wet façade is best suited for masonry walls. Due to the heavy and dense structure, a full-fledged mechanical fastening with high pull-off resistance is possible. Also, stone or concrete walls traditionally have high adhesion or can be primed in a special way for adhesive or combined fixing..
But the field of application of wet facades is not limited to stone capital buildings. Lightweight frame systems and wood-sheathed self-supporting insulated wire (SIP) are suitable for wet plastering if special aesthetic requirements are imposed on the facade. One has only to remember that SFTK well perceive holistic, monolithic bases. Cracks and other defects in the bearing layer quickly appear on the front surface, therefore, the frame sheathing plates must be reinforced with high-strength adhesives using fiberglass.
The most specific are systems that combine wet plaster with an external facade plane, under which there is a space for ventilation. The curtain wall system is executed on standard consoles with vertical profiles. A continuous preparatory lathing is sewn onto them and plastering is performed on a thin layer of insulation. This method of facade decoration is especially popular in regions with a harsh climate, where, in addition to protecting a rather thick layer of insulation, it is necessary to zone thermal insulation in order to effectively prevent the outflow of heat.
Design development and selection of materials for wet facade systems are hampered by a rather meager set of regulatory documents. In the domestic standardization system, SFTK are very modestly described in GOST 53785; the standard methodology of thermal engineering calculations is also used to determine the point of condensation of water vapor. Building standards of Western countries can bring more clarity: EIFS, EWIS and ETICS are the three main names for different types of facade systems for searching foreign regulatory documents.
The choice of a specific type of insulation is made taking into account a number of key characteristics:
- The required resistance to heat transfer determines both the specific characteristics of the material and the layer thickness.
- Optimum resistance to diffusion of water vapor is achieved by overlaying layers of thermal insulation of different density for more free penetration of moisture closer to the outer layer.
- Resistance to bursting and impact resistance are determined by the density of the thermal insulation layer immediately below the protective layer of plaster.
- Fire safety is one of the key aspects in finishing design. For example, it is not allowed to use polystyrene plates on the facades of high-rise buildings..
- Durability and resistance to freezing in a moisture-saturated state is the main argument in favor of synthetic slab insulation, if there is no unambiguous conclusion on the heat engineering part of the project.
In general, for the SFTC there are no highly specialized insulation materials. The technology allows you to freely use both synthetic polymer (EPS, polyurethane foam, PIR) and general-purpose mineral thermal insulation or their combination.
Protective layer device
In addition to the high level of responsibility regarding the methods of physically securing the system, there is a second stage of finishing that does not tolerate negligence. We are talking about applying a protective layer of plaster, which affects both the final strength of the coating and its durability and appearance..
First of all, you should forget about the self-preparation of the mixture and the use of plaster compounds of dubious quality that have not passed mandatory certification. Environmental requirements for facade decoration are not too strict, but the compliance of physical and mechanical characteristics is of decisive importance.
For protective plastering, water-based cement mixtures are used with the inclusion of a filler of a certain fraction and, as a rule, with the addition of polymerizing and air-entraining modifiers. The main difference between special plaster is the ability to pass water vapor in a sufficient volume, while maintaining high hydrophobicity from the outside.
The second aspect is strength characteristics. When applying plaster to the surface of the insulation, it is imperative to increase the adhesion of the latter by means of the recommended primers and strengthen the structure of the protective layer with both mesh and fiberglass. In this case, the overlap between the sheets of the reinforcing mesh should not be less than 40 values of the total thickness of the protective layer and decorative finish.
Decorative facade finishing
We have come to the final stage of the SFTK review – choosing the appropriate type of finish. In this regard, a wet facade gives, if not complete freedom, then certainly the widest choice among other known systems..
Traditionally, for decorating wet facades, plastering is used: “bark beetle”, textured plaster, gunning under the “fur coat”. The problem is that on large planes such a coating looks too monotonous, although the technology allows both jointing and relief separation of wall sections.
The second type is coloring. If, when applying the protective layer, it was carefully leveled, then it is quite permissible to use facade paints of almost all known types. However, as with plastering materials, caution should be exercised here: the decorative coating should not in any way reduce the characteristics of the protective layer in terms of vapor permeability and hydrophobicity.
Finally, there is a third type of wet facade finish. This includes prefabricated panel materials that are attached to the backing layer with an adhesive mixture. Usually this type of finish is used for lining the basement, where clinker bricks or natural stone can also be used..
But there are also special types of finishes for the entire surface of the walls, which, in addition to an attractive appearance, provide additional thermal insulation and support most of the technical characteristics of the used facade system..