End dams are needed at the discontinuous ends of the flashing over loose laid lintels to prevent water that enters the masonry above the lintel from flowing off the end and into the masonry at the window jamb. Without end dams, water accumulation can concentrate at this location, which contributes to the deterioration of the masonry. In addition, concentrating water in this location can lead to interior leakage problems.
Dealing with end dams at lintel flashings can be difficult. To work effectively, the front edge of the flashing must extend beyond the face of the wall. If this front edge is held back, water might flow around the end dam and remain in the wall.
If the end dam projects beyond the face of the wall, however, it is often unsightly. One way to handle this problem with metal flashings is to cut the front edge back at about a 30„a-degree angle from vertical. In this way, only the lower 1/2 to 1 inch of the end dam is exposed and the remainder is concealed with a mortar joint.
The same procedure can be used on flexible flashings with a metal drip edge. The metal drip edge can be bent up at the end dams and the front edge trimmed at a 30„a-degree angle, as described above.
It is also important to extend the front edge of the metal flashing or drip edge slightly past the surface of the masonry. The end dam must be formed in the flashing beyond the end of the steel lintel. If not, water flowing in the cavity can reach the top of the lintel and travel under the flashing.
I typically do not recommend the use of flexible flashing without a metal drip edge in this application. Flexible flashing generally does not provide a finished appearance where it projects from the wall.
I also recommend installing a sealant between the underside of the flashing and the brick below at the jambs of the loose laid lintel. With this approach, water cannot penetrate beneath the flashing and the lintel. The seal is needed with both rigid metal and flexible flashings. However, when flexible flashing is used without a metal drip edge, it is likely damaged when the sealant is cut away in the future.