Flashing Flat Roof Brick Wall

Follow the photo for illustrated instructions.
Flashing flat roof brick wall. These kinds of houses often have a roof that butts against a wall. I wonder if i need a new roof. Install base flashing under shingles or over metal roofing material. Here is a guide on how to install lead flashing to your roof.
Flashing on a wall above a flat roof. It may be quite a labor but it pays off with a strong roof. This video demonstrates where flashing could be leaking from on a brick wall. To install the roof wall flashing above the builder bent the top edge of the flashing into a 90 degree lip about 2 cm in width.
I have a flat roof adjoining a brick wall. The lead flashing seems a bit cracked and there is water leakage into the rooms below. It is commonly used in two story and side split houses. Lead seems very expensive and i wonder what the trade is using instead if at all.
Proper roof wall flashing example. Metal roof flashing can be use to seal gaps between roof walls. A couple of trades people have suggested i need new flashing.