Facade coating: which one to choose? What price for installation?

The choice of a facade plaster is complex. It must take into account, at the same time, strict technical constraints, sometimes unavoidable and more subjective notions, but just as compelling, linked to tastes and sensitivity aesthetic of each one. Industrialists have understood this dilemma. Today, they offer an infinite number of colors and finishes for each of the possible technical solutions. Alongside this abundance of constantly evolving novelties, traditional options, and sometimes even ancestral ones, do better than resist, retaining a significant share of the market.

A generic expression to designate solutions that are not very comparable

First of all, what does the concept of coating cover? The building trades are accustomed, according to fashions or the evolution of techniques, to deviate the meaning of words used daily. Literally, facade plaster is a coating applied to raw structural materials, to fill in irregularities and holes, so as to present a plan and sustainable. To protect this surface from bad weather, mold, fungi, to fireproof it, harden it or modify its surface condition, plasters and paints are used. Current facade covering materials, iintegrate in their formulations, the ingredients make it possible to simultaneously all or part of these operations, including personalt as desired, sometimes in a single application pass. Recently, facade plaster can also help complement insulation thermal and phonic habitat (light mortars).

For simplicity, use therefore names “facade coating” all the pasty technical solutions, ensuring at the same time, the protection, the dressing and the aesthetic finish of the walls. In contrast, the “cladding“is reserved for rigid architectural elements, having the same functions, but mechanically fixed to the facade.

3 methods, to achieve a single goal

There are three main families of facade coatings:

  • traditional coatings, formulated on site, based on hydraulic binders and mineral fillers set in reaction with water;
  • traditional plasters based on aerial binders, which harden on contact with air;
  • industrial coatings, based on binders hydraulic and / or aerial with the addition ofadjuvants.
  • monolayer or multilayer;
  • applicable by machine or manually;
  • suitable for new buildings or renovation:
  • Compatible with the majority of known materials;
  • with any kind of grain size
  • compatible with all kinds of surface finishes;
  • in a very wide range of shades;
  • for very specialized uses.

Each of these families comes in many variations, depending on the media, the specifics of the site, local weather conditions and the method of application.

Traditional lime and cement plasters

Known since antiquity, traditional plasters based on hydraulic lime and cement have long since made their mark. evidence and demonstrated their limits. These mortars are still commonly used for renovation work and systematically for interventions in historic monuments. Tinted in the mass using naturally colored sands, they blend particularly well into the local environment and are in harmony with old porous materials, such as limestone, rubble or brick. Providing a certain air permeability, lime plasters, in particular, are well known to leave “breathe“the heart of the wall, allowing water vapor transfers from the interior of the building to the atmosphere thus drying the deep wall structure. At the same time, these coatings form an effective barrier to external humidity. Lime mortars are also easy to spread, very adherent to the walls, flexible, malleable and insensitive to frost.

Cement plasters, which are more resistant, harder, and therefore more brittle, have low permeability and are more technically applicable. Today there are additives to improve the grip and malleability of cement mortars, but good compromises are obtained by mixing lime and cements, in varying proportions depending on the characteristics that one wishes to favor (bastard mortars) .

Traditional coatings are applied in 3 passes:

  • The gobetis, a thin liquid mortar (1 to 5 mm), is sprayed manually or using a mechanical device. He must stay rough to allow the voucher hooking up of the next layer.
  • The sided or plaster body, is applied after partial hardening (shrinkage) of the coating (3 to 7 days). From 15 to 20 mm thick, it is the layer ensuring the solidity of the plaster and the dressing of the surface.
  • The facing, determines the final rendering in color and surface appearance. This finish, thin (5 to 8 mm), is generally more generously dosed in binders.

The high thickness of these plasters (20 to 25 mm) is essential to avoid color nuances, particularly unsightly, to the right of supports of different kinds (ghosts). This is the case, for example, with the trace of the joints between bricks or concrete blocks.

Traditional coatings based on aerial binders

Like hydraulic lime, air lime (or fatty lime), is well suited to old buildings. Flexible, it is even better suited to rammed earth or earthen structures which, generally without foundations, work their whole life according to changes in atmospheric conditions. It does not damage the supports and easy to remove, thus facilitating the reuse of old materials. Finally, it is a healthy, ecological material, despite an unsatisfactory carbon footprint (manufacturing heating to 900 ° C) and durable, for which we find century-old works, still solid.

Conversely, aerial lime is subject to restrictive conditions of use and implementation:

  • material pasty, impractical to handle;
  • Irritating for the skin, it must be handled with impervious gloves;
  • Sensitive to climatic conditions during its application, the coatings must be made in mid-seasons (between 5 and 20 ° C), to avoid significant temperature gradients during drying, which is always long;
  • in case of dry winds, the fresh plaster must be humidified, lasting several days, under penalty of crazing and detachment;
  • the gel, before complete hardening, causes appearance variations surface and / or structural stratifications deep.
  • Cold (<20 ° C), extend the hold naturally long, several weeks;

The aerial lime plaster spreads in three layers, like hydraulic lime plasters, however, implementation constraints reserve this product for a few very specialized sites.

In general, traditional coatings no longer meet the manufacturing requirements of new residential houses and certain mechanized application methods.

Industrial coatings, based on hydraulic binders and additives.

For many years, manufacturers have been constantly developing and improving mortars only formulated for the confection coatings of exterior walls. Derived from traditional plasters, they are generally packaged in 20 or 25 kg bags. Wet, then applied to the machine in one thin layer (10 to 15 mm), they were designed in the 1970s to increase efficiency in the manufacture of large new real estate programs. Faced with the success of the product and the size of the market, manufacturers have diversified their production to adapt it to all situations. Today, therefore, there are ready-to-use plasters for all fields of application:

These products, from high technicalities, tinted in the mass, are increasingly versatile, a precious condition for adapting to surfaces made up of heterogeneous materials. These performances are made possible by the addition of organic fillers and / or specialized adjuvants which make it possible to facilitate their application, modify their characteristics and improve their performances.

By erasing or attenuating their constraints of use, industrial creations brilliantly sound the ragain plasters aerial lime.

The choice of surface finishes

Traditional, industrial, monolayer or multilayer, facade plasters allow all surface finishes. Smoothed, scraped, washed, ribbed, projected, tyrolean, crushed, the surface conditions meet strict aesthetic criteria, with no consequence on the resistance of the materials. Note, however, that the more a surface hasroughness, the more it retains dust, dirt or pollution and the more difficult it is to clean or paint.

Price of facade plasters

It is not easy to establish a coherent estimate, without study site-specific criteria (support, preparations, type and thickness of the coating, etc.). Just know that in general, the price of facade coatings varies increasing in the following order:

  1. industrial single-layer coatings;
  2. traditional multilayer plasters;
  3. restoration of old walls;

The products used and the companies consulted are also factors of significant differences between quotes. So do not hesitate to ask at least 3 opinions and costings different for your work.

On average, supply and installation included, count in All taxes included price :

  • between 20 and 40 € / m², for a single-layer coating;
  • between 30 and 70 € / m², for a multilayer coating;
  • up to 100 € / m², for a renovation of old walls.