Flashing and weep holes:
A flashing is a continuous sheet of impervious material that is used as a barrier against the passage of water, into the building – Weep holes drain water from the cavity to the exterior.
Used to prevent moisture from penetrating the roof edge to wet the masonry wall, at the intersection of roof and the parapet wall – Uses a base flashing and counter flashing to achieve the purpose – Roof membrane becomes the base flashing; counter flashing comes from the outer wall to cover the base flashing – Should be turned in 8” into the wall to prevent water penetration.
Used to catch the water that has penetrated the outer wall and to drain it through weep holes to the exterior – Internal flashings should be placed at the bottom of the wall cavity and at every location where the cavity is interrupted; at heads of windows and doors, at window sills, at shelf angles, and over exposed spandrel beams – Should be accompanied by a weep hole – Should be turned up 6” to 8” at the interior face of the wall and penetrate at least 2” into the back up wythe – Outside the wall, flashing should be carried at least 3/4” beyond the outside face and turned down at 45o angle.
It should be placed at every 24” c/c horizontally – Min. diameter for a weep hole is 1/4” – Made by inserting a short of rope laid in the mortar joint and later pulled out – Plastic tube and metal accessories should be provided to prevent insects from entering the cavity.
Material for flashing:
Made of sheet metal, UV resistant plastics, elastomeric compounds, or composite materials – Galvanized steel is unsuitable but stainless steel and copper are suitable; aluminum and lead are unsuitable.