It is the builders responsibillity to ensure that windows and doors are installed in such a way that water does not penetrate from the outer skin to the inner skin of the building envelope. The extent of the flashing will depend on local weather conditions. In some instances only sill flashings may be required. In others, jamb and head flashing may be required. For further information please refer to the relevant sections of the BCA
Jamb Flashing
Required in high window locations to ensure that water which enters between the window jamb and the outer skin is drained to the sill flashing
Where jamb flashing overlaps sill flashing, the overlap should extend the full depth of the sill flashing
Head Flashing
Provided to stop water wetting the inner skin by bridging across the window or door head.
Provided above any wall penetrations not specifically designed to stop water reaching the inner skin i.e exhaust fans and ventilation ducts.
Must protect horizontally a minimum of 150mm both sides past the opening.
Must be or approved materials to AS2904
Must be provided with weep holes to let the water out
Sill Flashing
Provided to stop water entering across underside of the window and wetting the inner skin
The window generates run off in down pours and sill flashing stops this water being blown across the cavity under the window
Some windows have drain holes which also direct water downwards into the cavity. The sill flashing also collects water which runs down the jamb flashing.
Must project a minimum of 150mm both sides past the opening
Must be of approved materials to AS 2904.
The brickwork must be provided with weep holes to let the water out
Special Care
Special care is required on windows with undersill drainage used in a non cavity situation such as single skin block work.
Where a subsill is used, stop ends must be fitted and sealed
Windows 
