House facade cork: spray-on natural cork

Recommendation points

• What is Liquid Cork?
• Useful properties of cork finishes
• Products on the Russian market
• The choice of the insulation system and preparation of the base
• Preparation of plaster mix
• Application technique

The appearance of cracks on the facade is one of the pressing problems of outdoor decoration. Cork spraying helps to eliminate the formation of “cobwebs” and at the same time gives the coating a number of amazing qualities. Today we will consider the features of liquid cork for facades and the technology of work.

What is Liquid Cork?

Facade cork can be considered a specific type of warm plaster. The unique properties of the bark of Mediterranean oak have long been known to mankind, but until recently this material was used mainly only for the manufacture of wine corks and linoleum. Spraying cork plaster on the facade is a rather extraordinary technology, owing its appearance to the rapid development of modern polymer chemistry.

The composition of cork plaster does not include components familiar to the layman, such as cement and sand. The filler is oak bark crumbs, which are formed as a by-product of the production of cork products. The binder is a set of acrylic polymers, the exact composition of which is kept secret by each manufacturer. The approximate ratio of cork granules to the mixed binder in the finished solution is about 10: 1.

Spray cork should not be confused with cork plaster. The latter is well suited for manual application, but requires a high quality base coat preparation. When gunning, a more sticky compound is used, which demonstrates high-quality adhesion to most building materials. In addition, spraying cork can be called one of the few methods of decorating houses with complex wall geometry, for example, domed.

Useful properties of cork finishes

The qualities of the sprayed cork can be conditionally divided into those that are important for the customer and those that are used by the manufacturer’s advertising strategy. There is no negative context in this, just some properties of the material are obvious and constant, regardless of origin, while others are more specific and may vary depending on the brand of material.

So, for the facade, the appearance and the period during which it is preserved are of primary importance. In this regard, cork coverings positively stand out among other materials: both texture and color are good, and the ability to survive movements in the base without consequences. Whether the epithet “cool” is appropriate in terms of appearance is up to the reader, but it is they who can describe the surface of the finish upon close examination and the sensation of touch. There is no problem with specifying a specific color: yes, cork colors are quite expensive, but very durable, and they are also very easy to use..

Now let’s move on to the technical qualities. Most manufacturers (which is not surprising) declare absolutely fantastic qualities: absolute hydrophobicity, vapor permeability, non-flammability and, as you might guess, excellent thermal insulation. Here you need to understand that a sprayed cork means a finishing layer of 3-5 mm, so heat-saving properties can be safely considered as the last thing.

As for the other qualities, they entirely depend on the composition of the coating: the fraction of the granules, the used binder components and their ratio. The stories about the absolute incombustibility of the cork are absolutely unfounded, the maximum that the leading manufacturers have achieved is self-extinguishing properties. Hydrophobicity, supposedly allowing corking pools, also looks like a very dubious claim..

Products on the Russian market

The best way to make sure that the material has the required qualities is to request samples from the manufacturer, stir them yourself, dry them and touch with your own hands what you will later have to deal with. Note that most suppliers are very willing to take this step..

ISOCORK is considered to be the most popular spray cork brand. According to some sources, this is a clone of the Italian manufacturer Subertres, according to others, the products are considered completely domestic development. The latter can be clearly seen in the dynamics of prices: during the period of rising prices for imported analogues, ISOCORK, on ​​the contrary, reduced the market value of its products. On average, these materials cover about 50 thousand m at the facilities of the Moscow region per year.², most of the reviews are positive. For facades, two series of cork coverings are presented – basic and refractory, the latter is intended for use in multi-storey construction.

Another popular manufacturer, called Cap-Cor, uses exclusively imported products in three varieties: façade, interior and roofing. It is not even a supplier of materials for cork coverings – the company is, in fact, a large department of a Moscow construction company. Therefore, the price for the performance of work is lower, and the level of technology mastery is purely professional. But you have to pay for everything: in terms of cost, Cap-Cor materials are superior to most popular brands, and therefore, for self-application, this material is the least profitable economically, although it is of consistently high quality..

The third “big fish” on the domestic market is NanoCork (N-Cork). This Russian supplier combines Western and domestic technologies, materials also come from different origins. Nano-Cork supplies three types of coatings in retail volumes, including façade and fireproof. The price of materials is slightly higher than that of the previous two manufacturers, while these coatings do not have any outstanding properties that analogues would not have..

The choice of the insulation system and preparation of the base

A review of the technology should begin with the fact that cork coatings can be used with or without external insulation. That is, a house made of sandwich panels is quite suitable for such a decoration, but there are nuances. One of them is the requirement to fill the joints with a special sealant and strengthen them correctly. The rest of the cork fully meets the requirements of movable bases. It can even process well-established log cabins, as a result, a very interesting effect of a monochrome “fur coat” is obtained, which exactly repeats the shape of the logs.

In the presence of insulation, the situation changes. On the one hand, the insulation acts as a damper, taking over most of the vibrations of the carrier layer. The question of impact resistance remains: although cork is a fairly resilient material, the presence of a base layer under it is strictly required. However, the base layer itself can be made directly by cork spraying, which is not dyed in order to save money. Thus, the total coating thickness can exceed 10-15 mm, while maintaining high resistance to impact loads.

Reinforcement of the base should be performed if mineral wool with a density below 150 kg / m acts as a heater³, not having a rigid outer layer. Polystyrene boards and similar materials are simply sealed at the joints with acrylic sealant. In this case, incompressible materials must necessarily have adhesive and mechanical attachment to the base. The metal fasteners present can be left unprotected if corrosion inhibitors are included in the coating, for example, zinc phosphate.

Wooden bases also do not need additional protection. Due to the hydrophobization of the surface, the wood does not get wet, therefore, a breeding ground for harmful organic matter does not form. Insect pests in cork-covered wooden products also do not settle due to the presence of a tough crust bound with polymer glue.

Preparation of plaster mix

Unlike cement and other mineral binders, the polymer has a fixed water absorption. This allows the manufacturer to specify the mixing water dosage with high precision. Small adjustments to the added water can be made to change consistency to the requirements of the spray equipment.

There are two forms of delivery of facade coating – in dry form and already mixed mixtures in an airtight bucket. A significant difference between them is in the weight of the delivered product; shipping the mixed mixture by courier services is more expensive. Differences in the quality of the material can only be observed if the cooking technology is violated..

Water is used to mix or dilute the liquid cork. Since the binder contains a complex of complex polymers, it is desirable that the water be deactivated (filtered). The presence of dissolved ions and the overall hardness do not play a significant role, but in the presence of active chemical elements (chlorine, iron), violations in polymerization (cracking) and a decrease in adhesion can be observed.

Both during dilution and during application, the uniformity of the finished mixture is extremely important, and a hint of delamination should not be allowed. Therefore, it is recommended to mix the cork exclusively with a construction mixer at an average (1.5-2 thousand rpm) speed.

Application technique

The pot life of the finished mixture depends on the amount of water in it and is at least 3-4 hours. This allows you to prepare the material in large portions, but the base itself must be completely prepared by the time of application. The latter implies cleaning from efflorescence and greasy stains, as well as subsequent dedusting (priming) with a special composition from the manufacturer of the spraying material.

The cork is applied in thin layers of 2–3 mm on a well-dried surface. With a capacity of one bag of 20-25 liters, one prepared portion is enough to cover an area of ​​up to 30 m² at a one-time application rate of 0.7-0.8 l / m². The total layer thickness is determined by the presence or absence of the base, the desired characteristics of heat conservation and hydrophobicity. In general, the mixture consumption is 3–3.5 l / m² with layer thickness less than 10 mm.

One of the most important economic factors for self-application of liquid cork is the cost of equipment. A set of equipment for a one-time performance of work will cost 15-20 thousand rubles, more professional machines cost over 100 thousand rubles with a much higher productivity. The latter type of equipment is often used by professional builders, while home craftsmen are content with amateur equipment, losing in the speed of finishing, but at the same time providing significant savings to the project. The expediency of a purchase is manifested, as a rule, in volumes over 100-150 m², where the contract budget turns out to be 2-3 times higher than the price of a compressor with a gun.

When applying the cork, it is necessary to carefully protect those surfaces where the composition should not get. For these reasons, it is preferable to finish the walls before facing the plinth and filing the soffits. The support system can be installed before starting work: spraying will provide additional protection for wood and metal structures.

It should be understood that cork is not used to correct the plane of the walls, but it can effectively fill fairly large local defects such as brickwork seams. The more irregularities of this kind, the less the thickness of the layer applied at one time..

Separately, it should be said about the adjustment of equipment parameters. Optimum for reliable and high-quality application is considered to be a torch width of 20–25 cm. At the same time, the working pressure of the pneumatics should be within 3-4 atmospheres. More intense spraying will cause the cork granules to rebound; with a lower head, the filler simply will not leave the tank, so only the dissolved binder will be sprayed.