Grid size for windows. Does it exist?

Hello dear homebuilders,

we are in the process of revising our planning. We want to reduce the height of a window and move it a bit further down. Now our house manufacturer said that we should only make the changes in 12.5cm increments. So both for the window size and the shift. Does anyone know why that is? Are the bricks in that size and they don't want them to be cut, or how could one explain that?

Best regards Thomas

Are the bricks in that size

Almost exactly guessed right. The grid of one eighth of a meter actually derives from brick dimensions. Today's brick sizes still build on that, but in earlier decades with solid bricks, a brick was indeed (including mortar joint) one stone (25 cm) long and one header (12.5 cm wide). In height, it's a bit less strict since jumbo formats are used, which practically cover three old layers in one step. Here you can admire how a wall looks when the planner doesn't care about the standard dimension.

we are in the process of revising our planning again.

It's a pity that it's so secret :-(

I have provided you the planning here: https://www.hausbau-forum.de/threads/wie-gefaellt-euch-meine-planung.39645/

I have made the plan available to you here:

That one cannot see the "relationships" of the dimension chains there - because almost no measurements are given - brings me to an important postscript, namely: applying the grid of the eighth of a meter to the openings is only "half the battle" - only when also applied to the wall sections does it make sense.