ᐅ Window connection for cavity wall construction

Hello, what is the correct window connection in a double-layer masonry wall where the outer window sill is made of facing bricks? For thermal reasons, the window is supposed to be installed within the cavity insulation. Now, I wanted to have the window sill built flush with the bottom frame. My window installer said that windows are always placed on the window sill (facing bricks) to prevent driving rain from getting into the cavity insulation. Is this true, or is there a reasonable solution? I wanted to position the facing bricks in front of the frame so that the frame does not appear so bulky. I would appreciate some advice.

Hello, I would advise against allowing the brick veneer to overlap the frame at the lower section because I believe it will be difficult to keep it watertight over time. If water penetrates the cavity insulation, the damage can become quite significant. I agree with the opinion of your window installer on this matter. If you want to study the topic thoroughly and in detail, I would recommend getting this book, which covers all the connections around windows and exterior doors very clearly:
Guideline for the installation of windows and exterior doors: with practical examples: ISBN-13: 978-3869500829

Alternatively, I might consider a special building component designed for use with brick veneers in this area; please see the attached image.