Oversizing of window areas

Hello everyone,

when measuring for facade work, it is generally common (according to VOB) to overmeasure window areas < 2.5 sqm (i.e. these are not deducted from the total area).

So far, so good.

Now I have asked myself to what extent a window that is directly adjacent to a balcony door can be deducted. To illustrate this, I have attached a picture: window and balcony are directly connected (no reveal or similar in between), the frames of door and window are directly adjacent.
Separately, the areas are 2.1 sqm (balcony door) and 1.9 sqm (double window) and would thus of course be overmeasured.
However, it would be logical for me if this area were deductible.

In various offers, the range of estimated sqm is very large overall (more than 30 sqm difference between the offer with the smallest vs. largest area).
Maybe this could be a point of application?

As far as I know, the opening is considered as a whole, because it is not the component that is installed that counts, but only the opening. In my opinion, this opening should therefore not be over-measured. However, it could happen that the reveals are calculated separately.

I basically see it the same way. According to the VOB, openings, niches, etc. up to an individual size of 2.5 sqm are measured separately. One could then of course say that windows and balcony doors are each two individual parts and thus should be considered individually... But I also think like Koempy that the opening itself counts here.

With 300 sqm total area, 30 sqm is 10% "error". This is not explained only by your element. Just ask...

Yes, I will definitely ask again. It's not 300 sqm. But there would be several such cases in total, amounting to about 15 sqm altogether.