Still one of the most common and inexpensive ways to finish exterior walls is plaster.
A house covered with a plaster layer not only has an excellent appearance, but also lasts much longer, since the plaster layer effectively protects the wall material from adverse external atmospheric influences. Currently, a large number of manufacturers offer a wide range of dry mixes and ready-made plaster solutions, of various composition and functionality. What kind of plasters it is advisable to use and for which wall materials we will consider with you in this article.
To perform plastering work, a special plaster solution is required.
It can be either in the form of a dry mixture (sold in bags), which must be mixed in water, or in the form of a ready-made mass (sold in buckets). The wall must be covered with plaster in order to level its outer surface, as well as to protect the wall material and the entire building from destructive atmospheric influences (sun, frost, rain). In most cases, the plaster mortar performs, along with the main functions, a number of additional ones, such as accelerating the drying process of a moistened wall, increasing its thermal insulation characteristics, etc.
There are two main functions of facade plaster, namely:
protective is, first of all, protection from various atmospheric precipitation, snow or rain. In addition, some types of plasters are able to effectively protect against external noise, limiting their penetration into the premises. There are a number of plasters, which to some extent are able to improve the thermal insulation characteristics of wall materials, reduce the thermal conductivity of the wall structure.
decorative – a qualitatively leveled surface of the wall and its uniformity is an excellent basis for the subsequent painting of the facade with special facade paints.
Along with this, the plaster layer itself can also act as a facade decoration, have an interesting color or original texture. In addition, the plaster layer is able to hide minor defects in the wall structure of walls, such as cracks, stains, heterogeneity in the use of wall materials.
The layer of applied plaster must not only be resistant to adverse atmospheric factors, but also be sufficiently durable and resistant to mechanical stress. In addition, each developer, first of all, is interested in the fact that the price of the plaster mixture and its consumption are not burdensome for the budget. An experienced contractor, in turn, evaluates the quality of the plaster on other parameters, such as setting speed, drying speed, workability, as well as ease of application to the surface and ease of rubbing.
before purchase.
Not when we should not forget that it is the manufacturer’s information printed on the packaging (bucket or bag) that is one of the most valuable sources of information.
It is from this source that you can obtain information with high reliability about the purpose of this plaster mixture, about the conditions for its use, about its additional characteristics.
As a rule, the manufacturer on the packaging provides information of the following order:
• type of plaster mixture – a specific type of plaster is indicated (thin-layer, restoration, cement-lime, cement, etc.),
• application – a description of what exactly this plaster is intended for, for which specific works (internal or external), whether it is suitable for facade work,
• the weight of a bucket or a bag – as a rule, it is from 25 to 30 kg,
• plaster consumption – this parameter allows you to determine with great accuracy the amount of plaster that must be purchased to complete the required amount of work. Consumption is indicated in kg. per square meter of area and layer thickness (usually 1 mm) (kg/m2/cm),
• temperature conditions of use – indicates the threshold of the maximum allowable high and low temperatures at which it is possible to perform finishing work using this plaster. This range is usually in the range of 5 – 200C,
• compressive strength – this parameter indicates how high the strength of the finished plaster after it is laid on the walls. The compressive strength is specified in N/mm2. The higher this value, the better
• adhesion – this parameter has the same units as compressive strength. The higher the value of this parameter, the better
• coefficient of resistance to diffusion of water vapor – the smaller this indicator, the greater the vapor permeability of this plaster composition.
This coefficient is denoted by the Latin letter µ,
• the maximum and minimum thickness of the plaster layer – the thickness of both its individual layers and the entire plaster coating as a whole is usually indicated.
Particular attention should be paid to the fact that self-prepared plaster (in a concrete mixer) is significantly inferior in quality to factory-made plaster. This is due to the fact that factory-made dry mixes, in addition to standard components (sand, cement and lime), have a number of special additives that significantly improve their characteristics, increase the simplicity and ease of working with them. Along with this, in “home” conditions it is quite difficult to create a plaster of a uniform consistency.
At the same time, its individual portions will differ significantly from each other, since you will not be able to dose the components that make up its composition with “pharmacy” accuracy. We strongly recommend not to experiment with “home-made” facade plasters, but to purchase them only from factory production.
Traditional plaster. The traditional plaster compositions used for finishing the exterior facades of houses include various types of mineral plasters. Their main component is lime or cement, which act as a binder. Since these components are of low cost, then finishing the house using these plaster compositions will be inexpensive.
Consider the main types of traditional plasters that can be used on the facade.
Cement-lime plasters. The composition of such plasters includes sand, lime, cement and water. Such plaster can be applied to any type of wall materials, as well as to any mineral base (on concrete walls, over brickwork, on cement fiber boards, etc.). As a rule, the thickness of the plaster layer ranges from 1 to 1.25 cm, with an average consumption of 11 to 16 kg/m2/cm.
“Homemade” plaster mortar, prepared directly at the construction site, contains only cement, lime, water and sand. The factory plaster mass, in addition to these components, contains special additives that significantly increase workability, inhibit moisture absorption, increase adhesion, and also accelerate or slow down setting.
Cement-lime plaster compositions made “by hand” must be applied to the wall surface in three stages (layers):
• spray (base layer) is applied with a thickness of 3 to 4 mm and serves to improve the adhesion of the plaster layer,
• the primer is applied with a thickness of about 8-15 mm, followed by smoothing,
• nakryvka – directly finishing plaster layer, which has a thickness of not more than 3 mm, is rubbed with a special grater to obtain as even a surface as possible. Plaster compositions of factory production, as a rule, do not require the first two stages (spray and soil). In addition, you can purchase additional ready-made masses of factory production for spraying bases with low adhesion (for example, concrete walls) or under plaster for manual application to walls.
Ready-made cement-lime plaster compositions for manual application contain a small amount of special additives in their composition. In their composition, they approach the plaster compositions, which are directly prepared at the construction site. Ready-made cement-lime plasters for machine application contain a number of additives that provide a longer setting time, and therefore easier application to the wall surface. These compositions can be applied both by machine (using a special plaster unit) and manually. Compared to ready-made plaster solutions for manual application, these compositions are of higher quality, but they also cost an order of magnitude more expensive.
If your walls have a very even surface, then fine-grained cement-lime plaster can be used to finish them. With its help, it is possible to perform a decorative coating on top of a layer of ordinary cement-lime plaster. This type of plaster should not be applied to the basement of the building, since due to the small thickness of the plaster layer (only 3-8 mm), its resistance to mechanical damage will be much less.
Features of cement-lime plasters:
• high resistance to moisture (but less than cement mortar),
• high level of vapor permeability,
• high ease of use (when applied to the wall and when grouting),
• high resistance to various mechanical damages,
• low cost. Another type of traditional plaster is cement plaster. It consists of a mixture of sand, cement and water. This type of putty is mainly recommended for finishing the basement parts of buildings, as well as fragments of external walls, especially those exposed to various mechanical stresses (near doorways, stairs, etc.).
In most cases, cement plaster is used as a leveling layer (base) for the subsequent application of vertical waterproofing in the construction of basement and foundation walls. This plaster composition can also be used as a spray for the subsequent application of a layer of cement-lime plaster. As a general rule, it should be applied in two coats (spray and primer), with the same layer thickness as when using cement-lime plasters. In most cases, this wall finish will require the application of an additional outer layer of finishing with thin-layer plaster or painting the surface with vapor-permeable paint.
Cement plaster mortar can be used to plaster the outer surface of walls with a layer thickness ranging from 6 to 20 mm, while its consumption is in the range from 14 to 18 kg/m2/cm.
Features of cement plasters:
• high resistance to moisture (higher than cement-lime plaster),
• poorly pass water vapor,
• quickly seize and harden (compared to cement-lime plaster compositions), which makes it somewhat difficult to work with them,
• subject to shrinkage due to fast setting, which as a result leads to the formation of cracks on the surface,
• has a high level of resistance to various mechanical damage,
• has a low cost. At present, plaster compositions containing white cement are widely represented on the building materials market, which makes it possible to use light-colored paints, an order of magnitude lighter than when using plaster compositions based on ordinary gray cement.