7 tips for choosing slopes for plastic windows

7 min

Plastic windows have long become an attribute of a modern apartment. They conquered the world with their practicality, excellent heat and sound insulation qualities, durability and appearance. But just placing plastic windows does not mean getting reliable protection from cold and drafts. It is equally important to choose the right slopes for plastic windows. A mistake can lead to moisture accumulating near the window, provoking the development of mold. Incorrectly selected slopes may need to be repaired more often than you would like. So let’s understand the nuances of making the right choice.

What should be the slope?

To begin with, it does not interfere with figuring out why slopes are needed at all. There are several reasons to put them:

  • a window with neatly lined slopes looks prettier than without them. Unaesthetic seams filled with polyurethane foam may remain after installation. If we are talking about an apartment, then this view will greatly spoil any interior, making it meaningless to carry out further repairs;
  • mounting foam, which is actively used when installing plastic windows, has excellent thermal insulation characteristics, but easily absorbs moisture. If it is not protected, it will soon become damp and collapse, and the window will lose its proper thermal insulation properties. It is especially important to protect the polyurethane foam from the outside of the window, but you should not forget about the internal slopes;
  • correctly executed slopes increase the level of heat and sound insulation of the window structure, protect it from condensation.

Therefore, window slopes must meet the following requirements:

  • not to spoil the performance of plastic windows, and even better – to improve them;
  • have durability not less than that of plastic windows, i.e. about 15-20 years old;
  • meet the general style of the window and interior;
  • external slopes must be resistant to precipitation, temperature extremes, and sunlight.

Types of slopes for plastic windows

Even 20-30 years ago, when plastic windows did not begin their triumphant march around the world, the slopes were simply plastered and then painted. That’s all the finish. Today there are a little more options:

  • plaster with subsequent painting is still in use;
  • drywall sheets made it possible to carry out work faster and achieve a more aesthetic result;
  • plastic slopes;
  • metal – a rarer design option for slopes, used in external cladding;
  • decorative stone is also used infrequently, suitable for both external and internal slopes.

To understand which slope is better for a plastic window, you need to familiarize yourself with the basic properties of each of the available options.

Plaster slopes

Plaster is used to create internal and external slopes. In the latter case, it is better to take the composition for facade work. The process of creating slopes consists in applying several layers of plaster and leveling them, after which a finishing layer of plaster is applied, then painting is done.

The advantages of plaster slopes:

  • relatively low cost of creation;
  • resistance to mechanical stress;
  • the ability to select plaster with the required set of characteristics, which makes such slopes universal;
  • lack of seams, unlike, for example, drywall. If there are no seams, then the surface is simpler in the finish, and there are fewer places of vulnerability;
  • ease of repair and upgrade. If desired, the slopes can be easily repainted, and the cracks that appear are elementary masked;
  • the ability to trim slopes of complex shapes.


  • the complexity of the work performed. To make the slopes aesthetic, you need to have plastering skills. In addition, you need to be patient, because each layer of plaster must dry out. In the process, dust and dirt are inevitable;
  • the frame of the plastic window and the plaster will not be able to become one whole, since they have not yet come up with a sealant that would have equally good adhesion to plastic and plaster, then during operation you may encounter cracks;
  • plaster has low thermal insulation properties (the exception is warm plaster), so that in winter the material can freeze, and there it is not far before condensation appears. An additional layer of mineral wool or foam insulation must not be installed under the plaster;
  • repair of slopes will have to be carried out within a few years, since cracks and shedding are frequent occurrences.

The plaster has enough cons, so if you are not a master plasterer, for whom it is not a problem to update slopes every few years, then it is better to look towards other options.

Plasterboard slopes

Drywall has become a versatile material that is used everywhere in finishing work. So the slopes were also faced with them. The installation process consists in installing the lathing (usually a metal corner is taken), on which sheets of drywall are attached. Insulation is laid between the slope and drywall. If the slopes are flat enough, then drywall can be glued directly to it using putty, glue or foam.

Drywall is used for finishing interior slopes, but some craftsmen risk using it in exterior decoration. In the latter case, only moisture-resistant sheets are chosen, which are protected with a layer of plaster.


  • low cost;
  • relatively simple and quick installation;
  • the ability to additionally insulate the slopes;
  • creating a perfectly flat surface without the need for a long and tedious leveling with a level and a spatula;
  • durability subject to installation technology.


  • drywall is afraid of moisture, so the accumulation of condensation will be fatal for it. Even a moisture-resistant material does not always tolerate such an effect normally, therefore more and more people are abandoning drywall in favor of other solutions. Using drywall for outdoor decoration is an extreme degree of risk and hindsight;
  • low mechanical strength – as a result of a more or less strong impact, cracks may appear;
  • as in the case of plaster, it is impossible to choose a sealant with the same adhesion to plastic and drywall, so in the future the appearance of cracks at the junction of two materials cannot be avoided;
  • with independent arrangement of slopes, certain skills will be needed;
  • drywall requires finishing, as well as preliminary filling of the joints.

Plastic slopes

Plastic slopes for windows are devoid of many of the disadvantages of plaster and drywall. This is the youngest cladding option, but it bypasses other solutions in popularity. Plastic panels are usually understood as sandwich panels, but in order to make the most competent choice, you should know that there are two types of plastic panels:

  • wall panels in which there are stiffeners between two sheets of plastic with voids between them. The thickness of such panels is about 1 cm, they are quite fragile, therefore they cannot be used on slopes more than 25 cm deep. They are produced in white and can imitate the structure of a tree. They allow you to quickly install, but low strength is their weak point. To insulate the slope, mineral wool or foam is used under the panel;

  • sandwich panels are a better option, because here a layer of polystyrene is used between the plastic sheets, which strengthens the panel and improves its thermal insulation properties. The thickness ranges from 8-36 mm, but 10 mm thick panels are recommended for window slopes.

Recently, sandwich panels are usually used, so we will talk about them. Their advantages include:

  • high speed of installation, no dust and dirt. The slopes will be installed within a few hours. In addition, additional finishing work, such as filling joints or painting the surface, is not required;
  • aesthetic smooth surface;
  • variety of appearance. The standard color of the plastic slope is white, but many companies are ready to offer slopes of different colors, as well as products that imitate different types of wood;
  • additional thermal insulation without the need to separately mount a layer of insulation;
  • since the window frame and the slope are made of the same material, they will expand in the same way, which means there are no cracks and drafts;
  • durability and no need for regular repairs;
  • moisture resistance.

Among the disadvantages:

  • a blow can violate the integrity of the panel, and in the presence of deformation, the entire slope will have to be changed – it will not work just to putty the crack, as is the case with plaster;
  • cost. You can find very inexpensive slopes, but they are unlikely to boast of high quality. Usually, cheap plastic quickly turns yellow in the sun, so the savings come in sideways.

Metal slopes

Metal is used for the exterior decoration of slopes, and it has been used since Soviet times. Today, this option for organizing slopes is not very common, but it is definitely worth considering due to the huge number of advantages:

  • aesthetics. Smooth metal can be painted in any color, therefore it can be combined with any facade;
  • resistance to temperature extremes, direct sunlight and high humidity;
  • durability;
  • maintainability.

Polymer-coated metal shows itself best of all, which retains its original appearance for a long time and is not afraid of corrosion.

The main disadvantage is the high price, but if you consider that you do not need to constantly repair cracks, then metal slopes are not the worst investment.

Other slope options

Much less often, but still the following types of slopes are used with plastic windows:

  • stone. As a rule, they are done when installing wooden windows. Artificial stone can be used for facing external and internal slopes. Such a window will look solid, but you will also have to spend money. In addition, it will be necessary to perform the installation correctly in order to maintain the aesthetics of the structure and its performance;

  • wooden slopes are even less often installed complete with plastic windows. This is an expensive pleasure that requires proper installation and specific care;

  • ceramic tile slopes are a great option for a bathroom and kitchen. It turns out to create a harmonious interior and get strong slopes that are resistant to moisture, sun and temperature extremes. The only caveat is the complexity of the installation. We’ll have to carefully measure everything and cut the tiles. This is why many people recommend using mosaics for this purpose.

If you are not sure that you can cope with the finishing of slopes yourself, it is better to contact the specialists – you will save time, money and nerves.

To be sure of the quality and durability of the slopes, you should contact the proven places. We recommend the company “MasterOtkosov” to residents of Moscow and the region, which quickly and efficiently install slopes for plastic windows… They offer a lot of different shades and textures to choose from, all work is carried out in 1 day, and plastic slopes serve for 25 years. On the company’s website, you can quickly calculate the cost of slopes and order a free expert consultation.

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Passionate about DIY for over 10 years and all the new tools, I give you through this blog all my advice, tips, tests in all areas: carpentry, electricity, masonry, gardening, home automation ...


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