ᐅ Issue After Window Replacement | Incorrect Measurements?

Dear forum,

This April, during a complete renovation of our semi-detached house, we had the windows replaced. A window company came to take all the measurements and then installed the new windows. Since we are adding an 18cm (7 inch) external thermal insulation system to the facade, the windows were positioned at the outer edge of the wall.

The problem is that the window installer only measured the outer reveal without removing the exterior plaster beforehand. As a result, the new windows, balcony doors, and front door are between 5 and 10 cm (2 to 4 inches) too narrow because there was a considerable layer of plaster.

My questions are as follows:

1. Who is responsible in a case like this? Who would potentially cover any resulting costs?
2. Is it even allowed to install windows only on the exterior plaster? Normally, they should be mounted directly onto the brickwork, right?
3. How could these windows be removed in the future? On the outside there will be the insulation system, and inside, according to the window installer, we should fix drywall panels with profiles onto the window to rebuild the reveal, since applying another 4cm (1.5 inches) of plaster per side on the existing interior plaster is not possible. (Besides, this would probably be very expensive because every corner etc. would have to be rebuilt.) If the windows ever need to be replaced again, would the entire drywall reveal have to be demolished?
4. Will there be no thermal bridge in the gap between the brick and the drywall panel? Behind it is only the thin layer of exterior plaster.

I have attached a photo—I hope you can see that the windows were installed only on the plaster.

I would really appreciate any answers 🙂

Really unfortunate situation.

firas21 schrieb:

1. Who is responsible in a case like this? Who would potentially have to cover the costs?

The well-known question of "responsibility." It’s enough to understand how it happened. It could be either the way you formulated your order or a communication error on the part of the window installer. If your order was unclear, you will likely have to come to some agreement with the window installer.
Even more important is that you agree on how to handle the situation. It seems you have already done that technically.

firas21 schrieb:

2. Is it even allowed to install the windows just onto the external render? Aren't they normally mounted directly onto the brickwork?
Is the window fixing definitely clear? If you suspect poor workmanship, first raise it with the window installer, or possibly have it reviewed by the trade association or an expert.
3. How could these windows be removed in the future? External insulation (ETICS) will be applied, and inside, according to the window fitter, drywall panels with profiles should be fixed to the window to restore the reveal, since you can’t simply add another 4cm (1.5 inches) of plaster per side over the existing interior plaster. (Apart from the likely high costs, since every edge, etc. would also need to be redone.) If the windows ever need to be replaced, would the entire drywall reveal have to be destroyed?
Considering the lifespan of windows, this isn’t really an issue. The drywall reveal will most likely need to be replaced at the same time.
4. Won’t there be a thermal bridge in the gap between the brick and drywall panel? There is only a thin layer of external render in front of it.

That will depend on the execution, which I cannot sufficiently assess from the photo. In no case will you have a "thermal bridge," just possibly a spot with less effective insulation.

Thank you for the quick response.

I was never informed that the windows would be made smaller, or that the exterior plaster would be removed.
If I had been told, it would not have been a problem at all.
The entire construction site is still at the shell stage, so having no windows for a few extra days would not have been an issue.

I see the solution with the drywall panels as a "last resort," as I can’t understand how it will ever be possible to properly replace the windows in the future.

The process is as follows:
The windows were installed flush with the outer edge of the wall. On the outside, a black tape was applied over the reveals, and on the inside, the gap between the window and the exterior plaster was filled with foam. Additionally, a white tape was applied at the bottom.

Kind regards

Maybe it’s also clearly visible here:

firas21 schrieb:

3. How could these windows be removed in the future?

Removing them without damage is not possible. A bit of interior plaster or reveal is the least of the issues; the real challenge is on the exterior with the ETICS (external thermal insulation composite system) or render system.

The measurement technician can only record actual conditions, not future ones. The thickness of plaster can at best be estimated, and the measurements are passed on to production. It is important to anchor in the masonry, not in the plaster—using brackets, by the way—because screwing through the middle of the profile is too risky on the reveal edge.

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