DIY plastic slopes for windows

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In this master class, one of the options for finishing the attic window slopes with plastic panels is given. The detailed step-by-step instructions with photographs describe two possible options for the base of the slopes – with an exact frame and with an approximate one. We will also talk about the advantages of plastic slopes..

offers you a master class on the device of slopes on a window with a sharp top. The lintel of the window is made of a thick metal profile, which rests on an embedded part to the wall masonry. The lintel above the window was laid in 1 brick, the walls in 2 bricks.

From the inside, the shape is changed using a box device with the desired boundaries. For this, stops were arranged on the walls and a frame with inclined edges was created, which was also fixed to the ceiling lathing. Inside it will be filled with mineral wool, from the side of the room it will be sheathed with gypsum board.

For work we need:

  1. Measuring tool set – tape measure, level, steel ruler.
  2. Hand tool set – retractable knife, hammer, hacksaw, pliers, foam gun.
  3. Power tool set – screwdriver, impact drill.


  1. Expanded polystyrene 50 mm – 2 sheets.
  2. Sandwich panel of plastic slopes – by the square of the slope, mounting profile.
  3. Mounting foam – 1 cylinder.
  4. Dowels, self-tapping screws, profile sections up to 1 m, adhesive tape.


The key point is precisely the correct setting of level marks and slopes. To do this, you need to carefully consider this process and carefully mark the outer edge of the mounting profile of the slopes on the window frame. Then connect them with lines, getting a solid border of the outer window trim. Along this border, you can install the end profile of the slope panel.

Having drawn the outer border, you can find out the level of fastening of the base, setting aside finishing layers from the line (in our case, the thickness of the plastic panel and the bosom is 30 mm).

PPR base

After marking, having received the upper and lower points, sheets of expanded polystyrene (PPR) can be installed at this level. From the outside of the PPR, you can fix the dowel-umbrellas (there is a section of brick), and from the inside, tighten it with self-tapping screws to the frame. Self-tapping screws must be provided with washers or metal gaskets.

DIY plastic slopes

After installation and adjustment in a level, all sinuses and crevices should be carefully foamed..

DIY plastic slopes

Plasterboard frame

If the frame is not assembled in advance in size, you can resort to a simplified method.

After installing the insulation boards, they should be cut approximately to the plane of the wall. Then install two connected CD-profiles on the PPR end and determine the plasterboard mounting plane. Then fix the profile with foam. After that, you can arrange the frame and edges of the frame..

DIY plastic slopes

Installation of profiles is carried out in the standard way described in our article. After the final opening, the frame cavity is insulated with mineral wool.

DIY plastic slopes

Installation of slopes

The slope panel is inserted from one side into the profile fixed along the border. To do this, we cut the panel to the required size and mount it in the profile. Then we align the free side to the required level and temporarily fix it on tape or in another convenient way.

DIY plastic slopes

The cavity between the PPR and the slope panel should be filled with polyurethane foam.

DIY plastic slopes

Attention! During initial fixation, the sinus should not be completely filled – deformations are possible due to hardening of the foam. Fill in in stages – first, spot styling, then solid.

Then we cut out and install the side walls in a similar way..

DIY plastic slopes

Note.The order of installation of the side and top walls is determined by the master.

After warming and finishing the slopes, the plane should be sewn up with plasterboard.

DIY plastic slopes

All crevices, sinuses and joints must be sealed. Polyurethane foam and insulation in the window area should be applied as widely as possible due to temperature differences.

DIY plastic slopes

Price of plastic slopes

Decorating slopes with special sandwich panels is a modern and very convenient solution that has a number of advantages:

  1. The material is 75% insulated.
  2. Factory planes are perfectly flat.
  3. The mounting profile ensures a perfect joint that does not crack and does not require a sealant.
  4. Slopes are mounted on foam, without drilling and rigid braces.
  5. The speed and ease of installation makes it possible to finish the slopes with your own hands, or makes the work of the master cheaper.

The range of appearance allows you to choose plastic slopes for any interior. The cost of panels and profiles ranges from 500 (15 mm thick) to 1000 rubles / running. m (thickness 25 mm) with a width of 250 mm. The price for the work in most cases coincides with the cost of a running meter of the slope.

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