Window connection in double-leaf masonry

Hello, what does the correct window connection look like in a cavity wall where the outer window sill is made of the façade clinker bricks? For thermal reasons, the window is to be installed in the cavity insulation. Now I wanted to have the window sill built against the lower frame. My window installer said that the windows are always placed on the window sill (clinker) so that driving rain does not get into the cavity insulation. Is this correct or is there a reasonable solution? I wanted to set the clinker bricks in front of the frame so that the frame does not appear so large. I ask for help.

Hello, I would advise against letting the bricks overlap the frame rebate at the lower area because I think you won’t be able to keep it watertight in the long run. If water then penetrates into the cavity insulation, the damage is known to be more severe. I quite agree with the statement of your window manufacturer. If you want to deal with the topic thoroughly and perfectly, I would get this book, as all connections in the area of windows / front doors are perfectly illustrated: Leitfaden zur Montage von Fenstern und Haustüren: mit Anwendungsbeispielen: ISBN-13: 978-3869500829 Alternatively, I might get a special component in this area in connection with bricks, picture attached