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From simple cleaning to complete repair, including the treatment of cracks, the maintenance of a facade raises many questions: nature of the support, restrictions of use, products to use...

Choose a facade cladding

Sun, rain, frost, pollen, moss and various pollutions, not to mention the slight movements of the ground... so many hazards to which the facades are subjected all year long and that nothing comes to protect except their fi nition. It eventually deteriorates and requires more or less intensive care. Disorders observed on the coating may also involve heavier operations that affect the masonry, or even the entire construction. We will only briefly discuss them.

First step: establish the diagnosis

Even if it is planned to use a company or a craftsman to renovate its facade, it is better to start by listing the defective points - to be completed if necessary with sketches or photos. They will make it possible to reconsider the question without necessarily being on the spot, even to ask for advice from a distance. Describe the symptoms as simply as possible on the affected areas: dirt, foam, peeling paint, stains, cracks, etc. Then identify the support, that is to say the finish by approaching the wall heat gun or the flame of a soldering lamp for example: unlike mineral finishes, organic coatings (synthetic products) melt and burn. And do not hesitate to extend the inspection beyond the facades: roof overhangs, gutters, joinery, shutters, railings, stairs... The aesthetics is not suitable for facades clogged with dust, pollen and air pollution.

Identify the main disorders

If the shade has also resisted well and no annoying symptoms (cracks for example) does occur, a good cleaning should suffice. On the other hand, if the color has passed, it will probably be necessary to renovate it. The same thing if it leaves marks on the fingers as soon as you pass your hand over it: this "chalking" results from a superficial disintegration of the finish due to bad weather and UV rays. Benign also microcracks that form a network of meshes on the surface of a coating.
Not to be confused with true cracks or crevices, this crazing does not pose any threat to the durability of the coating as linear microfiessures, and both disappear during erosion.

Refurbishment with an adapted painting

Still in good condition but a little shabby, a mineral support does not necessarily need to be re-coated. A painting can then suffice. Acrylic, pliolite, siloxane, mineral? You can compare their merits and their limits (See table). But if you want to get closer to a traditional fi nish (to enhance your heritage for example), a traditional plaster is more appropriate. With the exception of pliolites, the other paints and similar facade coverings are now in aqueous phase. This is obviously an advantage during application (no smell, dilution and cleaning tools with water, fast drying, etc.). Overall, it is also a good place for the environment, provided you do not get rid of residues anywhere: avoid throwing them in the sewer or in an evacuation ending in a septic tank! The ideal is to collect them in closed containers and to deposit them in a dump (inquire with your town hall). Their treatment is in line with the decree on specific diffuse waste (DDS), published in the Official Journal of 23 August 2012.

Old building: priority to traditional plaster

The choice of a coating in principle respect the style and age of a house, one usually distinguishes buildings built before the first half of XXe century and those built after this period. The oldest masonry is characterized by combinations of materials (wood, stone, brick...) and the use of mortars lacking cohesion. These constructions, lacking chaining, suffer from poor mechanical resistance and the resulting disorders: deformations, cracks, capillary rises, bursting due to frost, plaster break-offs, efflorescence *... All this must be taken into account in the choice of a new coating: it must be both flexible enough to resist cracking, waterproof to rainwater but permeable to water vapor to allow the wall to evacuate excess moisture ( especially in the case of old walls). Such requirements exclude coatings lacking permeability and argue for a traditional lime-based coating. With the cited qualities, the latter adds antiseptic properties that reduce the development of mosses and bacteria (thus the clogging of the facades). In addition, it makes it possible to incorporate an armature frame on a fi xed support. In return, the implementation of a traditional coating is not within the reach of all and falls under different standards. And it is necessary to count with the slowness of its catch (several weeks).
* Moisture-soluble water salts that appear in crystallized form on the surface of a masonry as water evaporates. On exterior coatings, it is carbonation.

New build: a wider choice of finish

The constructions of the second half of XXe century use standardized materials (bricks or blocks) assembled using mortars dosed industrially. More homogeneous than their elders, they also leave more room for maneuver in choosing a coating. If it is not essential to opt for a traditional product, lime is not to be discarded either. Thin or thicker, these bastardized coatings enjoy the benefits of hydraulic binders (cement) and in particular a faster implementation. Manual or projected, it can be limited to a single pass for a single-layer product, provided that the masonry is in perfect condition. As soon as the substrate is weak or when the finish (other than scraped) requires it, a monolayer coating must be applied in two passes, or preceded by a gobetis. Gobetis and finishing use the same product, applied differently: first pass erect and tight but not smoothed; second pass projected on the first at the beginning of taking. The other bastarded coatings apply in two layers (roughened and trimmed on the one hand, finishing on the other). The mix also offers a shorter setting time and greater surface hardness (better abrasion resistance). In addition to the compatibility with old lime plaster (aerial or hydraulic), this type of plaster can also be applied to organic coatings (plaster body covered with plastic plaster or thick organic coating). But, again, remains to master the implementation (manual or projected).

Do or have done?

Intervening on one or more exterior walls is synonymous with constraints and major work. We must take into account the weather, get equipment (ladders and scaffolding), find the availability that will complete the work in the time allowed... In addition, any surface started must in principle be completed in the wake to avoid traces of recovery. To this requirement is added the technicality specific to the implementation (manual or mechanical) of coatings. This type of construction site is therefore to be entrusted to a company, if possible equipped with one of the following qualifications Qualibat: 2121 (masonry reclamation), 6111 (painting and technical refinement current), 6112 (technical confirmed), 6121 (refacing in painting). capeb.fr or travaux.qualibat.com

Facade: Which coating to choose?: facade

Apart from any other criteria (aspect of the final result, for example), the choice of a paint or a coating applicable to the roller is the only reasonably conceivable option for an amateur.

The opinion of an expert *

When one intervenes on a frontage, it is the reading of the frame which must dictate the solution. In compliance with a number of technical and aesthetic requirements: precise identification of pathologies, compatibility of finishes with their supports, respect of color codes in force... Do not hesitate to ask qualified interlocutors. "
* Sylvain Rippol, director of market façade and technical products, at Tollens.

Facade: Which coating to choose?: choose

Whether it is paint or plaster, contrasting hues are often at the origin of original effects, even spectacular... If this tempts you, check beforehand that no local regulation is there opposite.

And the air lime?

Greasy or lean depending on the purity of the limestone, the aerated lime (after calcination and hydration) serves as a binder to ensure the taking of a mixture, in contact with water. This lime is of calcium (CL: Calcium Lime) or dolomitic (DL: Dolomitic Lime) type. The mixes that it gives rise to tend to support tender, but their intake is very slow (several weeks or more). This is why lime CL or DL ​​can be mixed with natural hydraulic lime which hardens more quickly (in contact with water then air).

Facade: Which coating to choose?: which

Applying a coating requires a certain habit to adjust the thickness of the passes uniformly... Especially since the surfaces are by nature important!

Some standards

Façade products are governed by various standards. The main ones are:
NF T36-005 (paints and varnishes),
NF T30-801 to 803 (microporous paints for outdoor use),
NF T30- 701 to 706 (thick plastic coatings),
NF EN 998-1 (mortars of mineral coatings).
The implementation is also subject to several NF standards (often from unified technical documents, DTU):
NF P74-201 (painting work of the building),
NF EN 13914-1 (design, preparation and application of exterior coatings),
NF P15-201 (DTU 26.1 mortar plasters),
NF P 74-202-1 / A1 and A2 (DTU 59.2 thick plastic coatings on concrete and hydraulic coatings).
NF DTU 42.1 (refurbishment of facades in service by impermeability coatings based on polymers) and its part 1-2: general criteria for the choice of materials.

Cracks and crevices

Not to be confused with cracks, cracks or crevices are wider and deeper, to the point of crossing the masonry. These disorders express the multiple constraints that can undergo a construction. Some are inherent in the normal aging of components that work differently from each other (the supports and lintels of bays compared to neighboring areas in particular), while others result from poor workmanship (no expansion joint between two buildings, chaining vertical...), or even external causes (ground settlement). If cracks and crevices can be filled with masonry putty (preceded by a bottom seal for seconds), it is better to know first whether these disorders are stabilized or not. For this, we must put witnesses on both sides of the cracks (pieces of glass sealed with plaster or slider gauges glued), then check their condition after several months. Depending on the importance of the movements, structural reinforcement (underpinning, stabilization injections, etc.) must be considered by a professional. If the cracks that pose problems of impermeability can be treated with a semi-thick coating (CSR), the cracks, they, disappear only after marouflage of a frame of fabric of glass in the first pass of coating ( or a coating of organic facing, RPE). Another option is thermal insulation from the outside (ITE). Barely longer than a clean-up, the ITE definitely remedies the thermal deficiencies of the envelope (see our file on the topic of insulation, System D, n° 804, January 2013).

The traditional coating in three layers

A traditional coating has three layers: gobetis for hanging, roughing for waterproofing and flatness, and finishing. Each of them must offer a decreasing mechanical strength so that all the coating hangs correctly.
• The gobetis, or layer of attachment, makes use of a fluid mortar, without lime but rich in hydraulic binder (cement) to adhere well to the support, sodden beforehand. With a thickness of 5 to 8 mm, this first pass should not dry too quickly to avoid the risk of cracks.
• The sided, or plaster body, applies 48 hours later. From 15 to 20 mm thick, it is used to waterproof the wall and to erase most of the defects that it still has.
• The last pass contains pigments and sand to give the coating its final hue and texture. Finishing layer, it is applied a few hours after the sided.

Facade: Which coating to choose?: choose

To project a coating implies to control the dosage, the flow, the distance of projection, as well as the speed of progression... All this conditions the final result.

Paintings: which product for which support?

The different paints used to renovate a facade
Type of productCompatible supportsAdvantagesdisadvantages

Acrylic paint

All types of non-powdery paints (including pliolite), hydraulic or organic coatings
in aqueous phase, RPE (thick plastic coatings)

• Economic
• Compatible with microcracks and cracking
• Easy to implement
• Dry in a few hours
• Recoatable after 24 hours max

• Low permeability to water vapor
• Less durability than other products (especially at the entry level)

Pliolite paint
(elastomeric resin patented by Good Year)

Porous and powdery bottoms, including old paintings

• Adherence with or without primary
• Coverage
• Drying in any weather (or almost)
• Microporous
• Resistance to fouling, efflorescence, mold, temperature variations (blistering factor)
• Durability (resistance to UV rays, frost, sea climate
and aging...)

• Solvents (odors, etc.)
• Incompatible with universal dyes (factory tinted)
• Incompatible with soft coatings (waterproofing or waterproofing), organic plasters (plastered paints)
• Does not necessarily resist stagnant water,
cracking
• Does not apply in a thick layer (therefore can not cover a stucco with a pronounced relief)

Hydropliolite paint
(pliolite in aqueous dispersion)

Porous and powdery bottoms, including old paintings

• All the advantages of acrylics and pliolites
• Compatibility with universal dyes (dyeable on site), soft coatings, organic plaster
• Let the support breathe
• Enhanced adhesion and color stability

• Not very compatible with low temperatures and humidity
• Less adherence to pliolites
• Does not apply in thick layers

Siloxane and polysiloxane paint (resins derived from silicone)

All types of non-powdery paints (including pliolite)
and mineral coatings

• Advantages of acrylic products
• Good resistance to frost, dirt, UV rays
• High permeability to water vapor (higher than mineral paints)
• Machine-tintable (wide range of colors)
• Clear version usable as water repellent

• Requires removing old, less permeable finish

Mineral painting
(based on potassium silicate)

Traditional facades (lime plaster, silicate, stone and other raw mineral supports or old painted backgrounds...), ITE processes (thermal insulation from the outside)

• Advantages of acrylic products
• Water repellent barrier: Potassium silicate reacts with lime (contained in the cement of an absorbent floor)
• Permeability to water vapor
• Covering
• Resistant to UV rays, aging, pollution and aggressive atmospheres
• Decorative aspect thanks to natural pigments (mineral dyes)

• Incompatible with fatty substances in solvent-based finishes
• Stripping (sanding) essential before a solvent finish

Coatings similar to facade paints

Type of productCompatible supportsAdvantagesdisadvantages

Semi-thick coating (CSR) *
(based on acrylic copolymers
with or without polysiloxane resins in aqueous dispersion)

Any adherent paint (except polyurethane and epoxy), RPE (up to i1 **) and hydraulic,
ITE processes, tiling, glass paste or small format porcelain stoneware

• Advantages of acrylic products
• Well adapted to recent build
• Let the support breathe
• Applicable in 1 to 3 layers (with or without reinforcement)
to fill cracks up to 2 mm
• Implementation close to the painting
• Resistance to fouling, micro-organisms
and bad weather...
• Variable rendering depending on roll type (long wool fibers, honeycomb foam, honeycomb, rubber, etc.)
• Tilt possible (depending on product)
• Waterproofing facades (depending on product)
• Opacifying power
• Wide range of colors

• Incompatibility with polyurethane, epoxy and RPE paints from
of i2 ** (to be stripped)
• Reduced thickness (1.5 mm): to be applied in two layers on bare support

Thick plastic coating (RPE) (based on mineral fillers and resin in aqueous dispersion)

Acrylic or pliolite paints, ITE processes, hydraulic coatings

• Advantages of acrylic products
• Single layer
• Applicable to the roller (1.5 to 6 mm depending on the type of roll)
• Permeable to water vapor
• Fungicide and antifouling
• Possible use on cracks (with reinforcement mesh)
• Complement of waterproofing (with water, but not
with water vapor)

• Incompatible with plaster or plaster and lime plaster
• Underlay necessary to regulate the absorption of the bottom or its porosity if flourishing
• To be stripped before applying a hydraulic coating (cement and / or lime)

* CSR is also called renovator facades or waterproof systems.
** Required levels of waterproofing against infiltrating cracks: • i1 (cracks up to 0.2 mm): waterproofing obtained in a single layer of 300 g / m2 • i2 (cracks up to 0.5 mm): 2 layers of 300 g / m2 • i3 (cracks up to 1 mm): 2 coats of 400 g / m2 • i4 (cracks up to 2 mm): reinforcement grid and 3 layers of 400 g / m2.


Video Instruction: ProPERLA Exterior Facade Coating, water repellent, wall moisture, wall protection, beading effect