DIY window slopes

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In the article, we will consider topical issues of the device of internal window slopes. We will discuss all the pros and cons of certain design solutions and materials. Step by step we will consider the technology of installation of plaster, plastic, plasterboard slopes.

DIY window slopes

How the slope works

Internal slopes are an integral part of the window system, which performs several tasks at once. It would be a mistake to believe that they are intended only to decoratively compensate for the difference between the width of the window block and the wall, close the window mounting elements and give its appearance, integrity and aesthetics. The main function of a well-assembled slope is thermal insulation of the window structure, shifting the dew point outside the room. Obviously, the greatest heat loss occurs in the window area, in other words, this is the most problematic area from this point of view. Only in the complex (window + window sill + slopes + ebb + facade and interior decoration) can you effectively solve the issues of thermal insulation of the window opening. In the foreground are the thermal characteristics of the materials that make up the slopes, as well as strict adherence to the technologies for their installation. Unfortunately, our technology is not so hot as always. For example, few of the installers of window systems, builders-finishers know that according to GOST R 52749-2007, the layer of polyurethane foam, which fills the gap between the window and the opening, must be closed from the inside with a vapor barrier material – special mastic or tape. Outside, between the quarter and the window profile, it is necessary to install a waterproof elastic tape (PSUL). We will consider in more detail the installation technology and issues of acceptance of plastic windows in the following articles.

The choice of the slope material and the method of its installation depends on the design features of the walls, the type of window block, design preferences, the developer’s budget and many other criteria. At the moment, the most common slopes are made of plasterboard, plastic, as well as plastered with cement mortar. Modern wooden windows are often framed by slopes of various types of wood, cork.

Preparation for the installation of slopes

The first step is to check the correctness of the installation of the window unit, so that possible inaccuracies can be corrected in advance, and not be tormented halfway over the question: “how to do it, by level or by window.” Properly constructed slopes will only highlight problems with windows. Unfortunately, for certain reasons, there are very frequent cases of poor-quality manufacturing and installation of very popular nowadays PVC products. For example, the presence of vertical and horizontal deviations, curvature of profiles and other unpleasant “little things”.

DIY window slopes

All vertical deflections of the window are controlled by a plumb line. To do this, it is necessary to fix it first above one, then above another vertical profile of the window block and measure the distance from the plastic to the cord, stretched under the weight of the metal cone, above and below with a tape measure – these indicators should be equal. With a short rack level, you can check the horizontalness of the lower profile of a narrow window. In the case of oversized products, we recommend using the hydro level to put marks on vertical profiles, including on the “impost” (vertical rack), and then measurements are taken with a tape measure to the bottom edge of the window.

Mutually horizontal marks set by the water level make it possible to determine whether adjacent, closely spaced windows are at the same height, for example, this is very important on bay windows, balconies, showcases …

The evenness / curvature of the window profiles is controlled by pulling along the outer lines of the window frame with a control cord. By measuring and comparing the diagonals, you can check the presence of deformations and distortions that violate the rectangularity of the installed product.

Examine window profiles carefully for scratches, chips, or other damage. Pay special attention to the glass unit – there should be no cracks, scratches, air bubbles.

DIY window slopes

Check how the doors open and close in all positions, there are no rubbing, wedging.

If you are satisfied with the installation quality of the window block, its safety and appearance, then you can proceed directly to the installation of slopes.

Before starting work on the construction of slopes, it is necessary to carry out a whole range of preparatory dismantling works:

  • trim off obvious excess foam,
  • knock down the remnants of old plaster slopes,
  • remove moving, poorly adhered brickwork,
  • make grooves for entering the window sill into the wall,
  • remove anchor plates (if they interfere with the installation of slopes),
  • cover the foam with a vapor barrier material,
  • remove the protective film from the windows,
  • seal up possible through holes leading to the street or into the enclosing structures, as well as all cracks and faults with foam or mortar.

Attention! To avoid damage to the frame, window sill and glass unit, carefully cover all vulnerable surfaces with durable sheet materials during dismantling work..

Slope plaster

More recently, due to the lack of a modern variety of building materials, there was no alternative to plaster slopes. There is now plenty to choose from, and the proportion of plastered window slopes is steadily declining. Perhaps only a very conservative developer is ready to apply the “good old plaster”.

DIY window slopes

This finishing method has a lot of disadvantages:

  1. Poor sound insulation. The complete absence of thermal insulation, which leads to overcooling of the window profile and glass unit – as a result, we have almost guaranteed condensation, the appearance of fungus and even freezing of the slope.
  2. Formation of cracks at the junction of the slope to the window block due to the large difference in the coefficients of thermal expansion, as well as the almost zero adhesion of cement mortars to plastic or wood.
  3. Long term of plastering work, about 2-3 days, due to the need to withstand the initial layers until complete setting and intermediate drying, plus the obligatory puttying and finishing.
  4. Labor intensity, technological complexity of processes, starting from preparation of the solution and ending with the formation of vertical and downward-facing planes.
  5. Dirty and wet work.

The advantages of plaster slopes include:

  • low cost of materials,
  • resistance to mechanical stress,
  • lack of joints, edging, framing,
  • the possibility of finishing a slope of any width and shape, including arches of various radii,
  • environmental friendliness.

In order not to contaminate and not scratch the window block, it is necessary to start plastering the slopes by carefully gluing the window with polyethylene, which is fixed to the frame with masking tape. Particular attention should be paid to the protection of the fittings, since the ingress of sand particles from the solution has an extremely negative effect on its functionality and durability.

You can make slopes after the main areas of the walls have been plastered, preferably before installing the window sill. It all starts with the installation of plaster strips, without which it is impossible to obtain a high quality product. Competent installation of lighthouses is a guarantee of the quality of the plaster planes, so we recommend not to spare time for this work.

Sometimes plastering of walls and slopes is carried out in parallel, in a complex, using special corner beacons, “squares” on the outer edges of the slope. They are galvanized profiles, in cross-section similar to the well-known paint corners, only with wide mesh shelves. The corner beacon not only helps to make a quality plane, but also makes the corner much stronger, reinforcing it. To set a corner in two planes at the same time, you need to have a certain skill and serious practical experience, it is especially difficult to do this with large unevenness of the base, therefore they are used only by a narrow circle of professionals who have appreciated this useful element. In most cases, the craftsmen first plaster the walls, and then, on the finished plane along the slope line in various ways (for mortar, dowels or pressure plates), they fix the trapezoidal rule, the sharp edge of which will serve as a support and beacon to form the outer corner.

Another beacon is installed near the window frame. To do this, a ridge from the solution is thrown along the line of its location, after which the plaster lighthouse is pressed with the help of a level to a certain depth, followed by a pause for at least several hours – the lighthouse should become motionless.

Now you can fill the space between the beacons with a solution, leveling it with a scraper, cutting off the excess of a slightly frozen mixture with an even metal rail, slightly exceeding the width of the slope. Leave a strobe at the bottom of the window for the window sill to enter the wall.

After the solution has hardened, we remove the rule by moving it along the wall away from the slope. After a while, it will be possible to close up the untreated section of the wall, which was under the rule.

Attention! We recommend removing the plaster beacons from the planes with a fresh mortar, since during drying, the cement-sand mass shrinks, and the guides turn out to be on top of the planes. Moreover, under the influence of the rule and grades, the zinc coating of the lighthouses is very often damaged, as a result of which abundant traces of rust appear through the plaster and putty..

For the correct installation of beacons, use a plumb line or a high-quality long level.

Make a template to control the light turn of the slope from durable sheet material.

Observe the technological breaks to dry the layers. Do not try to completely make slopes of large thickness on one window in one shift – this is a sure way to form cracks and delamination. Better to do a rough plastering on several windows at once, and transfer the end of work and grout to the next day.

DIY window slopes

For good adhesion of the plaster to the base, use a galvanized mesh. To ensure good adhesion, be sure to prime the surfaces with deep-penetrating compounds. Above the window, a concrete lintel is often used to strengthen the brickwork, it and other similar smooth products should be treated with a primer containing sand based on various resins, for example, Betonkontakt or ST16.

The use of alabaster to speed up the setting of the cement-sand mortar helps to plaster the upper slope. The main thing here is to correctly dose the gypsum content in order to have time to apply and level the solution, this can only be determined empirically.

Installation of plastic slopes

Slopes made of polymer panels (cellular plastic, foamed PVC, sandwich panels) surpass the options with plaster in many performance characteristics. That is why plastic slopes, along with plastic windows, have become so popular with our compatriots..

  1. PVC slopes are absolutely moisture resistant, so they are not afraid of condensation.
  2. They have a smooth and even surface, which does not require additional finishing, putty, painting. They can be washed.
  3. High-quality plastic slopes are resistant to ultraviolet light and temperature extremes; with proper installation, they have a service life corresponding to the service life of windows.
  4. The panels from which such slopes are made have good sound and heat insulation properties, due to the cellular structure of the plastic or the porosity of the insulating layer of sandwich panels (polyurethane foam, extruded foam). In addition, the installation system of plastic slopes allows you to use a layer of mineral wool as an additional insulating element.
  5. Installation of plastic slopes is carried out dry, very quickly, with a minimum amount of debris and dust.

DIY window slopes

Naturally, plastic slopes have some disadvantages:

  1. Thin single layer PVC slopes can bend under pressure.
  2. Also, they are largely subject to point mechanical effects, while they are not repaired..
  3. The end part of the plastic panel must be closed with a corner or F-shaped frame.
  4. Difficulty fitting the slope to the unevenness of the wall.
  5. Installation of plastic slopes is carried out using an expensive power tool (hammer drill, grinder, screwdriver).
  6. Quite high cost of a set of materials for the device of slopes.
  7. They raise many questions among adherents of environmentally friendly building materials..

It is possible to make plastic slopes only after installing the window sill.

The device of plastic slopes begins with the installation of a starting profile, most often U-shaped. It is screwed on the very edge of the window block with a step of about 100 mm using 9-mm self-tapping screws for metal with a drill-LN, the so-called “bugs”. We recommend carrying out this operation along the line marked on the window profile with a chopping cord. Some starter profiles for the installation of slopes snap into the plastic frame before installing the window. When purchasing such fastening strips, you should clarify whether the window and starter profiles are compatible.

DIY window slopes

The next step is cutting the plastic to fit the slopes. Practice shows that the optimal adaptation for these purposes is a disc tool, for example a small grinder.

Now directly fastening the panels. There are several options, the most common of which and technically sound is foaming. This method is good in that the foam in the body of the slope significantly increases the deflection strength of the finished plastic product. In this case, the polyurethane foam is both heat insulating and adhesive material. The main task of the foreman is to accurately set the slope along a plumb line and in accordance with the given dawn, as well as prevent possible displacement of the panels under the influence of expanding foam. Usually for this, a set of wedges is installed along the outer edge of the slope, the plastic slope is pressed against them and fixed with paper masking tape, which is glued to the front side of the panels and to the walls.

It is better to fix the slope to the foam in stages. First, the space near the window is foamed (about 50 mm is a cold zone, a probable “dew point”), then the panels are mechanically fixed with pre-prepared linings and tape, then the voids in the middle and outer parts are filled with foam. After the foam has hardened, the linings and wedges are removed.

We recommend using only professional foam from well-known manufacturers, especially since many of them have weakly expanding adhesive polyurethane foams in their product line..

Another method of fastening, which the manufacturers of PVC slopes are actively promoting, is screwing the plastic to the embedded element in the area of ​​the outer edge of the slope. Usually, a narrow wooden strip is used for this, drilled along the line of the outer corner. There are several pitfalls here: the end of the plastic and the mounting rail should be covered with an angular frame, it is extremely difficult to put the wooden beacon in the design position with high quality due to the various irregularities of the main walls, the plastic itself is sprinkled with self-tapping screws “through the body”, therefore, their heads should be recessed and covered with a decorative corner.

Some companies producing complete window systems offer the use of two-piece brackets made of millimeter galvanized metal, which are fixed with dowels on the mineral base of the slope. After aligning the brackets, the panels are fixed to their flat shelf using double-sided mounting tape.

The options for attaching plastic panels to any sub-base advertised on the websites of manufacturers of PVC products with compounds such as contact glue or liquid nails looks generally fantastic, unless you pre-finish the slope with plasterboard or plaster.

No matter how the installation of plastic slopes is made, they will have to be framed with a corner. It is cut at 45 ° and glued with various compounds, temporarily fixing it with masking tape.

Even with very careful installation and use of corner joints, gaps remain at the joints of the slope elements, which must be sealed without fail. Note that white silicone turns yellow over time, and its pores, albeit not numerous, are clogged with dust, so it is better to use putties that are resistant to UV and dirt.

We make plasterboard slopes, GVL

Plasterboard slopes are most common in the decoration of window openings. They are devoid of most of the disadvantages of plaster and plastic slopes..

DIY window slopes

  1. Plasterboard slopes are mounted quite quickly, however, unlike PVC options, it takes time to finish them.
  2. Behind the sheet material, it is possible to place a layer of insulation – mineral wool, foam or polyurethane foam, which is excluded when plastering.
  3. There are a lot of options for plasterboard facing: painting; wallpapering; finishing with polymer and stone materials, cork, bamboo.
  4. Plasterboard slopes do not have cracks, do not require the use of sealants and frames.
  5. The good maintainability of plasterboard slopes is that the damaged surface can be easily restored with putty, repainted.
  6. Drywall is considered the most environmentally friendly material.

According to opponents of drywall slopes, their main disadvantage is their weak resistance to moisture. In fairness, it should be said that this statement is more related to the layers of finishing. It is possible to allow the formation of such an amount of condensate that can deform drywall only with gross mistakes made during the selection and installation of window blocks, window sills and slopes. If everything is done correctly, there will be no condensation at all.

For the device of slopes, you should use a moisture-resistant green gypsum board or gypsum plasterboard. Some craftsmen process the back side of prepared-sized sheets with a deep-penetrating primer, paying special attention to the places of the cuts, the ends. An acrylic sealant applied to the inside of the starting profile acts as a waterproofing. When painting, the choice is best made in favor of latex compositions intended for wet rooms.

As well as when working with PVC slopes, a starter strip made of extruded plastic should be installed on windows for installing drywall on windows. Manufacturers of drywall systems produce specialized profiles for these purposes. They are fixed every 100 mm with self-tapping screws-LN, you will need a screwdriver with an extended bit. The starting profiles must be mounted along the lines from the paint cord, at the points where drilling takes place, they are tightly pressed against the window frame. Screws should be tightened at low speeds so as not to disrupt the threads in the plastic.

DIY window slopes

There is a technology in which drywall sheets are wound up behind the window profile, and not mounted end-to-end with it. In this case, it is necessary to cut out some of the foam near the window and, definitely, remove the mounting plates. Naturally, this slightly enhances the thermal conductivity of the unit. However, sometimes this option is preferable, for example, if the window canopies are too close to the edge of the window block and there is too little space for mounting the starting profile..

The next step will be to cut the drywall strips for the slopes. This is done quite simply – using a flat metal rail 2 meters long and a special knife for cutting gypsum boards. The front layer of paper is cut along the edge of the rule, the sheet is broken and folded, and then, by significantly tilting the knife blade, you can cut the paper from the back. The unevenness of the plaster mass, formed when the sheet is fractured, are removed with a plasterboard plane. When measuring, take into account the angle of dawn of the slope and possible unevenness of the wall. Most craftsmen make gypsum plasterboard strips 30 – 40 mm wider than the intended size, this excess after installation is cut along the plane of the wall or according to the rule, it easily breaks and is removed.

Attention! Before cutting the gypsum board, remove the sealed with paper, rolled factory chamfer. This is about 50-60 mm along the long side of the sheet..

If the window sill has not yet been installed, measure the length of the strips from the bottom of the window profile so that after the device of the slopes there is a niche for the entry of the window sill.

After fitting the sheet material, we recommend dry fitting the slopes.

If everything is ok, the last adjustments have been made – we start editing. As a rule, various combined options are used here, in which the operation of filling the space near the window with foam remains the same point. But in the area of ​​the wall, the sheets are fixed either with self-tapping screws to the wall posts of the metal frame, pre-exposed by the edge and in the plane of the slope, or glued to the mineral substrates using Perlfix type mounting adhesive from Knauf. Considering the fact that puttying is inevitable – temporary fixing of slopes is carried out in a variety of ways: self-tapping screws, dowels, spacers, tape, etc..

In the places where the side slopes adjoin to the upper knife, a chamfer is cut off to seal the joints of the sheets with putty. Next, the drywall is primed, and you can proceed to puttying and finishing the slopes.


Now some conclusions can be drawn.

Plaster slopes, due to poor thermal insulation, cannot be used in combination with narrow plastic and aluminum window blocks. The only way to use them is on wide wooden windows, where there is a slightly greater distance between the beginning of the slope and the street. And, of course, they will be quite appropriate on interior and exterior entrance doors. According to the technical characteristics, PVC slopes are suitable for any conditions. It seems that with proper installation, they are the most practical, but a plastic product is sometimes simply impossible to fit into some design solutions, for example, as an addition to expensive wooden windows. Plasterboard slopes are able to fulfill all the tasks set by modern building codes. Their often-mentioned drawback, the obligatory finish, is rather an undeniable advantage – they look great in any interior, with any windows and doors..

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