The Ontario Building Code | Extension of Flashing
9.20.13.4. Extension of Flashing
(1) When installed beneath jointed masonry window sills and jointed masonry copings or over the heads of openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings, flashing shall extend from the front edge of the masonry up behind the sill or lintel.
(2) A flashing may be omitted when the masonry at the sill of a wall opening or the top of a wall is protected by an impervious non-jointed masonry coping that conforms to Article 9.20.13.12.
In Plain Language
Flashing must extend far enough, as set out in this article, to properly capture and redirect water away from the wall assembly.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.