Basement Window Wells
Basement windows that extend below ground level require window wells (Figure 51) to direct water away from them. Corrugated steel frames are commonly used for this purpose.
When the backfill is not a granular material,the bottom of the window well should be drained by a pipe or hole 150 mm (6 in) in diameter installed through the backfill material to the drain pipe and filled with crushed stone.
Where a bedroom window with sliders, casement or inward-opening awning opens into a window well, it must have a clearance of at least 760 mm (30 in.) in front of the window to allow for escape in the event of emergency. Additional clearance is required for outward-opening awning windows.
Source : Canada Mortgage and Housing Corporation (CMHC)