Add a window later

Especially when you buy an existing building, the division of the building is in very few cases exactly in line with your own ideas. In addition to the room layout, this also applies to the existing windows. For this reason, we have put together instructions for you below on how to retrofit a window. You will also find a lot of additional information that is particularly important when installing windows at a later date.

Numerous reasons for the subsequent installation of a window

A house does not always correspond to the expectations of its current residents or. owner. In old buildings in particular, rooms such as toilets, bathrooms or storage rooms are often designed without windows. If a conversion or change of use takes place, the subsequent installation of a window is often considered. But before you start, certain arrangements must be made.

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  • Determination whether a window can be retrofitted from a static view
  • Verification required official building permits
  • In many cases approval of the neighbors
  • Determination of the window size
  • Construction planning for the correct construction

Static check

To determine if all of the building stations at the position you determine a new window "tolerates ", you should definitely consult a structural engineer or architect. This can give you binding about whether there are static concerns about your project or not.

Building permits and consent of neighbors

The building authority that is responsible for you can quickly tell you whether a building permit is required or not. In most cases this will almost certainly be the case. In addition, the neighbors must also agree as soon as certain distances to the neighboring property are not reached. He can refuse if he doesn't want you to be able to look over his shoulder practically all the time. Here it is also not decisive whether the ground floor or an upper floor is used.

Determine window size

Based on the statements of your structural engineer and then on the recognized rules of house construction, you can now derive the size of your window. There are no really standardized and fixed window sizes in Germany. Rather, these are related to the size of the room. How exactly you determine the optimal size of a window can be found in the linked article.

Structural execution of the subsequent installation of a window

In the construction journal you will find articles and instructions for the actual window installation, also for plastering windows and of course also for window and door installation according to RAL. We also provide you with instructions for building walls in the house journal. Therefore, the following instructions for retrofitting a window refer to the essential steps that are not affected by these detailed instructions.

Step-by-step instructions for retrofitting a window

  • Lintels of the appropriate length
  • Fastening material for the window lintels
  • window
  • Bricks
  • Mortar (€ 7.79 at Amazon *)
  • Plaster
  • Depending on the window installation, different building materials, which depend on the selected installation technology
  • Cover film
  • Tool for processing the existing wall (chisel, concrete milling machine, etc.)
  • Concrete mixer or drill (48,00 € at Amazon *) with stirringquirl
  • Mortar bucket
  • Different fillers and trowels for walls
  • Various trowels and fillers (example white smoothing chest) for plastering
  • Spirit level
  • Director
  • String
  • Tool for window installation
  • Tool for the concrete window setting anchor
  • possibly wheelbarrow
  • possibly scaffolding
  • Maybe rubble container

1. First steps: Slot for the window strip

If all permits are obtained, the corresponding plan is also available. This plan corresponding to the affected wall now the exact position of the windows fall, ie centrally above the window.

Depending on the size of the window, the slot for the falls is 30 to 40 cm wider than the actual windows. On each of the later window sides, the fall with 15 to 20 cm must rest on the masonry.

2. Fit and fasten window lintels

There is talk of window lintels because with a conventional wall thickness, two lintels are always used next to each other. So first insert the inner lintel and fasten it with the associated fastening material. Proceed in exactly the same way with the second lintel.

3. Chisel out the window opening

Now you can continue to break through the wall. Draw the opening (also depending on the length of the lintel) on each side 10 to 15 cm wider than the window will be later.

4th. Brick window reveal

Now you wall again on the side down to the actual size of the actual window niche minus the required plaster thickness and seal (Kompi tape) in order to achieve a straight, vertical finish. On the parapet, too, wall a horizontal row of stones across the entire width until the required dimensions are reached.

5. Plastering the reveal

If you want to assemble your windows according to RAL guidelines, you now have to fill the reveal straight and finely so that the sealing tape (Kompi-Tape) actually seals optimally later.

6th. Place and install windows

Now you can set the window, fix it and finally plaster the reveal (if necessary). Finally, you need to set the new window.

7th. Alternative approach

If you get the green light from the structural engineer (especially with very large, wide windows), you can make the breakthrough to the full length of the window lintels and then build up the masonry that will later support the lintels.

Tips & Tricks The subsequent installation of a window is a very demanding job. The assembly of windows and doors according to RAL guidelines alone is so demanding that even some (not appropriately certified) craft businesses have difficulties with it.If you want to enlarge an existing window niche in order to subsequently build in larger windows, do not forget to take precautions for an inexpensive disposal of the old window.