Flashings for a chimney consists of a front apron, side step flshings and a rear gutter with cover flashings. When a chimney is sited at a ridge, the back gutter is replaced by a saddle at each side.
Depending upon the type of tiles or slate, the side flashings will either be detailed with soakers (Code 3 Lead in most cases) or as step and cover flashings in one.
Chimney flashings can be fabricated by leadwelding or bossing. Code 4 lead is the minimum thickness to use, but if bossing is the method used then Code 5 lead is preferable for the back gutter.
For roof pitches above 30 deg (or above 20 deg in sheltered of moderate exposure) the side flashings can be finished 10mm back from the front corner. When this detail is used, however, it is essential that the front apron is properly turned at the corner so that an adequate lap is provided where the side flashing covers the apron.