Problem calculating the parapet height for a worktop running into the window

I can already tell that it’s getting more complicated than I thought.

No, then you have – at least me – misunderstood: it is not more complicated (in the sense of more back and forth and calculating all over the place, or a higher number of unknowns), but it is simply that you need more patience. It’s not rocket science, and all the required data will come to you – just not so that you have them all before the game starts.

Let’s see how I manage to implement this.

In this respect, the rule applies: wait and drink tea – as construction progress comes, advice comes. It would be no unheard-of idea for the masons to lay the last layer in the window opening in a second work step, nor unusual for the window maker to take measurements from facts instead of plans (I say that as a former window manufacturer).