Window replacement, reveal insulation, and windowsill

I measured again and with a 20mm XPS board, it doesn't work. If I insert a hex key into the lower hinge, the distance from the key to the wall is 25mm.

Question.
1. Would the 10mm XPS (Ultrament Bauplatte) be sufficient as insulation for my wall construction?
2. How many mm should I allow for the full-surface adhesive + plaster?
3. Would the 10mm XPS board support the weight of a window sill made of Dekton?
4. Is XPS hazardous to health, for example because of fire retardants?

I measured again and with a 20mm XPS board I don’t make it. If I insert a hex key for the lower hinge, it’s 25mm from the key to the wall.

Question.
1. Would 10mm XPS (Ultrament construction board) be enough insulation for my wall construction?
2. How many mm should I allow for full-surface adhesive + plaster?
3. Would the 10mm XPS board support the weight of a windowsill made of Dekton?
4. Is XPS hazardous to health, e.g. because of fire retardants?

:rolleyes: Just do it instead of worrying about trifles.

1. What do the calculations of an engineering office say?
2. As much as you want to apply
3. The board supports nothing. The windowsill simply rests on it
4. If you eat it, I can understand that it’s hazardous

End of irony.

JUST DO IT!!! Adhesives are a few mm; plaster almost zero if you only smooth and sand. And yes, the windowsill couldn’t care less what it rests on. And no, XPS won’t harm you at all.