Installing a window sill on your own – what could be easier

Recommendation points

• How to choose a windowsill
• How to determine the required size of the window sill
• When to install a window sill
• How to prepare a place for mounting a window sill
• How to install and fix a window sill
• How to protect a window sill from damage

Almost any modern renovation involves the replacement of windows, and few of the developers come to mind to leave an old wooden or asbestos-cement window sill painted with oil paint. Many people are familiar with the situation when the “windows” finished their work and left, and the new window sill remained lonely near the wall. What to do next? Look for masters again?

The window sill is an essential element of a modern interior. At the same time, it performs not only a decorative function, not only serves as a stand for flowers and household appliances, but also actively participates in the air exchange processes that occur near the windows. Protection of the lower part of the window opening from possible condensation and mechanical damage, thermal insulation of one of the most problematic areas of the outer walls – this is what the true, utilitarian purpose of a well-installed window sill consists of.

How to choose a windowsill

At the moment, it is not difficult to buy a window sill made of durable material that is resistant to sunlight and temperature extremes, and is dimensionally stable. There are a lot of options on the market, each of which has its pros and cons. However, the main problems of choice come down more to the implementation of design solutions and the thickness of the wallet.

Due to the low cost, from 55 rubles per running meter, and good technical characteristics, PVC window sills are most common. They have similar properties to plastic windows, as they are made of the same UV-resistant, moisture-proof materials. The multi-chamber structure with frequent bulkheads gives them high compressive strength and excellent thermal insulation properties.

Light weight, ease of cutting and processing greatly facilitate the process of installing plastic window sills. It is not a problem to choose the color of the finished product, including imitation wood and marble. The color can be transmitted both “in bulk”, for example brown, or as a film according to the RAL catalog. Most often, such window sills are made to match the window profile. The front surface of the PVC window sill has a matte texture or is lacquered. It is easy to find a plastic window sill that is the right size for almost any particular occasion. In large hardware stores, products are often available with a thickness of 18-22 mm, a width of 100 to 600 mm. The strips are 4 or 6 meters long, but, as a rule, you can order their cutting on the spot, or buy a window sill of any length. The main disadvantages of plastic window sills can be considered a weak resistance to local damage: scratches, chips, breakdowns. They practically do not lend themselves to restoration.

Window sills made of MDF and chipboard can have a laminated top layer, cork or wood veneer. At a low price, they perfectly imitate expensive materials, including natural stone. Such products have good performance and thermal insulation properties. They are easy enough to cut and install..

If the protective coating of MDF and chipboard window sills is not damaged, then they are not exposed to moisture, do not warp or swell. Laminate window sills are difficult to scratch. Their cost per running meter can be from 150 to 1200 rubles with a width of 30 cm.

Window sills made of coniferous and hardwood species are the best fit for wooden windows, have a very beautiful texture, visible under a transparent protective coating, but they can also be painted in any color. They are also a good heat insulator..

Depending on the properties of the wood used, they have to a certain extent high bending strength, resistance to scratches and dents, and besides, they are easy to repair. The thickness of timber sills is usually about 40 mm. Among the shortcomings, one can note the need to ensure their waterproofing, which completely depends on the condition and quality of the protective and decorative coating, which requires periodic renewal. Prices for products from oak, hornbeam, beech, cherry, ash can hardly be called affordable. A high-quality solid pine sill will “pull” at least 1000 rubles per running meter, larch – 1800, beech – 3000, oak – 5000.

Window sills made of natural stone – marble, granite or onyx, are perhaps the most expensive of all on the market (from 3000 rubles per running meter), but their classic beauty, sophistication and prestige leaves no one indifferent. The assets of such products include expressive texture, the ability to choose color, size, shape, style of processing corners and edges. Stone windowsills are not afraid of water and temperature changes, but to some extent they are susceptible to pollution due to the porosity of natural materials. Being quite fragile, natural stone products are well repaired. The large weight, as well as the complexity of processing, make their installation somewhat difficult. Natural stone window sills do not have thermal insulation properties.

Models of window sills made of artificial stone have operational advantages – resistance to chemical pollution, relatively low thermal conductivity. Troubles (in the low price category of similar products) can be caused by scratches on the front surface and its fading. Of course, they are cheaper than analogues made from natural materials..

How to determine the required size of the window sill

In order for the window sill to serve for a long time, to be comfortable and functional, it must not only be correctly installed, but also correctly calculated its dimensions. In some cases, it makes sense to make a window sill at the factory according to the exact dimensions. This problem is especially serious when working with a stone, since it is quite difficult to process, and it is very good if you do not need to adjust anything locally. Window sills made of MDF and chipboard can be ordered with a fully processed edge, which should also not be cut off, as it reliably protects the product from moisture.

The length of the finished product should be greater than the width of the window so that the window sill fits into the walls. Typically, the line of vertical slopes is released from 30 to 50 mm on each side. For example, if the width of the window is 1000 mm, then it would be logical to order the window sill 100 mm larger, 20 of which will go to the light turn of the slopes, 80 – to the side outlets (40 mm each). In the area of ​​the balcony block, one side of the window sill cuts into the wall, and near the door it should hang slightly, about 10 mm, over a short vertical slope.

The width of the window sill is mainly determined by the depth of the window opening. As a rule, the overhang of the window sill is made about 30-50 mm from the wall. This size is explained by the fact that too wide a window sill can impede the free circulation of warm air coming from heating radiators, which can lead to the formation of condensation on the surface of the glass units and side slopes. With a large overhang, the bending strength of the structure is significantly reduced.

To correctly determine the desired width of the window sill, it is necessary to perform the main finishing of the outer wall – plaster, drywall. It will be quite enough to have installed beacons or a metal frame. Measurements are made with a tape measure from the window to a cord stretched in the plane of the wall or a rule set across the opening.

Attention! It should be noted that a window sill of about 10 mm enters under the frame, resting against the installation strip of a plastic window or a quarter of a wooden profile.

It is especially difficult to measure non-standard window sills, such as on rounded walls, bay windows, kitchen countertops windowsills. Sometimes the window is deployed in the opening, then if you want to have an equally protruding cornice of the window sill, its width will have to be made uneven. In all these cases, we recommend inviting specialists from the organization where you will order them to make templates and patterns. The most accurate, flawless products are obtained from measurements made with geodetic equipment such as a total station. Roulette and a cardboard sheet do not always help out.

The main principle is simple: “Measure seven times – order once”.

When to install a window sill

If you decide to simply change the windows while maintaining the entire interior decoration of the premises, then there is nothing special to wait – you can start immediately after the foam dries.

But in the case of a major overhaul, the matter is a little more complicated. The reason for this is the vulnerability of the surfaces of an installed prematurely expensive product. In the process of carrying out extensive repair and construction work, when a large number of employees, guests from contractors (air conditioners, installers of security systems, installers of stretch ceilings, furniture assemblers …) are at the facility, it is extremely difficult to keep the windowsill intact. A flat horizontal surface, like a magnet, pulls to place a tool on it, a small, and not very, building material, put a cup of coffee, step with your foot in order to reach a high ceiling. As a result, the replacement of the window sill and the alteration of the slopes due to “out of nowhere” appeared scratches, dents, chips, persistent chemical stains.

Many practicing builders have come to the conclusion that the installation of the window sill should be done at the very last moment, just before finishing. Naturally, by this time the whole complex of preparatory work must be completed, including the walls and slopes have been mounted and even plastered..

How to prepare a place for mounting a window sill

Depending on the type of product, its material and thickness, as well as on the chosen method of fastening, we will prepare the base. First of all, it is necessary to remove all loose, protruding elements of the wall on which the window sill will rest, these are loose bricks, stubborn plaster, installation wedges, fasteners, embedded parts. If, during dismantling work, through holes have formed on the street, or in the enclosing structures, it is recommended to foam them.

You also need to prepare grooves in the wall for entering the window sill, here you cannot do without the use of a small grinder and a perforator. If the slopes are sheathed with plasterboard or plastered, then their plane must be interrupted not below the window profile in order to form a technological niche.

Next, you should restore the masonry, and along the lighthouses, pour a flat area from a durable moisture-resistant solution to the specified height. For mounting the window sill on polyurethane foam, it is advisable to have a gap of about 20 mm from the bottom of the product to the top of the installation site, so that the tube of the mounting gun can be brought into the area of ​​the window frame. To install a heavy stone window sill on the layer of most special adhesives, only 5 mm is required, that is, from the bottom of the window, the platform should be lowered by 35 mm, where 30 mm will be the thickness of the window sill.

If the outer wall is sheathed with plasterboard on a metal frame, a horizontal lintel should be placed at the correct height under the window. A common mistake novice plasterboard installers make is setting it too high..

A very important point in the preparatory work is to check the evenness of the lower edge of the window block. Certain problems are caused by poorly made or incorrectly installed PVC windows. Very often there are burrs at the junctions of the vertical and lower horizontal profiles, which do not make it possible to firmly press the window sill to the window – they need to be cut off with a knife. Another common defect is the shape of the lower profile in the form of one or more arcs curved upwards with their middle. Its presence can be easily checked by stretching a thread along the lower edge of the window from corner to corner. If a thin plastic window sill can be easily pressed against the window with wedges or foam, then with rigid products made from other materials everything is much more complicated, they only emphasize all the irregularities. As a result, there are very ugly cracks that will have to be sealed with all kinds of sealants. The reality is that even in new buildings of the elite class, it is necessary to repair the plastic window blocks installed by the builders – to cut out the foam from under the window, remove wedges and fasteners, dismantle the glass unit and level the PVC profile in various ways. Sometimes the case ends with a complete reinstallation or replacement of defective windows.

How to install and fix a window sill

No matter how accurately we made preliminary measurements, before installation, the window sill often has to be cut a little, especially in places where it enters the walls. Wood and MDF, chipboard are best cut with a jigsaw with a metal saw, but a plastic or stone window sill – with a grinder with a diamond disc.

To firmly press the window sill to the window, it is necessary to use wooden or plastic wedges. They are harvested from the calculation of the thickness of the product and are installed near the window lintel with an interval of 400-500 mm. Some craftsmen prefer to glue them to the substrate in advance so that they do not move during installation. The correct selection of wedges is checked by fitting the windowsill dry – the product should fit tightly.

The installation profile (window plate) should be carefully coated with silicone to seal the junction, the protruding mass can be subsequently cut off. It is also recommended to cover the end parts of the window sill made of MDF or chipboard with a layer of sealant, especially if there is damage to the protective coating.

The sill is installed in its place and centered relative to the window axis or the lines of the side slopes. Wedges are also installed under its front part, adjusting the level of the sill. In most cases, the cornice of the window sill is made below its base, pressed against the window by 2-3 mm, so that moisture does not accumulate near the junction.

A window sill made of MDF, chipboard, wood, plastic can be additionally fixed by screwing it with long self-tapping screws through the window mounting profile, for this you need to remove the external ebb.

So that the expanding foam does not squeeze the window sill up, you need to put 2-3 spacers going from the product to the upper part of the slope. We recommend installing flat wooden beams along the entire length of the window sill and on top to distribute the pressure from the spacers. It is convenient to adjust them using wedges. Options with placing a load from scrap materials on the windowsill sometimes play a cruel joke with the craftsmen, everything ends up with a re-installation.

Now you can foam the space under the windowsill. The foam should be applied sparingly, but evenly, without gaps, not forgetting that it expands strongly. Carefully fill the places where the side parts of the window sill enter the wall with foam, keep in mind – this is an important element of thermal insulation.

Stone window sills are not recommended to be mounted on foam, as there are cases when during its expansion a marble product was broken along the veins. It is better to install them on special glue, for example, CM117, CM115 and the like. For window sills made of onyx and light marble, it is better to use white glue, which will not leave marks if accidentally hit on the front surface.

With a comb with a tooth of the required size, about 6-8 mm, the adhesive composition, preferably in one continuous movement, is evenly leveled on a previously prepared base. The notched trowel should be guided as vertically as possible to ensure the same height of the ridges. With an even trowel, the stone window sill is covered with glue on the back side with a thin layer and installed in the design position.

If the window sill has a large overhang, then special corner brackets are used to fix it. They are fixed with one shoulder on the load-bearing wall with an interval of up to 500 mm, but not less than three pieces per product. Often this part of the bracket is recessed into the lining and sealed with mortars. The bottom sill is screwed to the consoles by means of short cylindrical screws.

After the foam or glue is completely dry, it is usually ready the next day, you can remove the spacers, install the end caps and start sealing the joints..

How to protect a window sill from damage

The first thing you need to pay attention to is the correct storage of window sills at the facility. Products made of wood, PVC, chipboard are best stored in pairs, with front surfaces facing each other, between which soft pads should be inserted. Stone windowsills are stored in an upright position, they should stand on two bars with an edge, leaning against the wall at a slight angle.

Before installing any window sill, it must be covered with a sheet of polyethylene using masking tape, or a special film that does not leave adhesive traces. Remember that there is still a lot of painting and installation work ahead, and this is the danger of dirt and mechanical deformation..

Attention! The factory protective film must be removed before installing the window sill in order to be able to check the quality and integrity of the front cover.

Window sills made of natural stone are capable of absorbing various substances with the formation of difficult-to-remove stains, therefore, after installation, they are immediately treated with protective compounds that close the pores of the front surface.

After installation on top of the film, strips of plasterboard, gypsum plasterboard or other similar materials should be laid precisely cut to the visible contour of the window sill.

It is recommended to preserve marble products with a protective wooden shield, paying special attention to the cornice of the product. The hanging end is the most vulnerable place, it is closed with a bar sewn in front. The casing must be securely fixed in the opening and rest on the polished surface through soft pads.

One must not overlook another very important nuance that directly affects the correct functioning and durability of the window sill – the distance between the bottom of the window sill and the heating radiator should not be less than 100 mm.