Technical Center - Your resources, all in one place.
Flashing Details
Overview The purpose for flashing is to direct water to the exterior of the building, and to prevent moisture from deteriorating steel angles or other building components. In addition, it serves to move any moisture out away from the inside of the wall.
The following details were designed to accomplish both goals. Modification to these details is normal, however, the changes should always focus on the primary objectives for flashing. There are some details that vary from standards practiced by the brick industry, however, it is our belief that these variations are a more practical approach. These details are available on discs, using CAD software.
** THE RESPONSIBILITY FOR SPECIFYING THESE ALTERNATIVES
BELONGS TO THE DESIGNER OR ENGINEER **
General Installation Considerations
When flashing needs splicing, the ends should be overlapped a minimum of 4" (100mm) and sealed with a compatible mastic.
Corner flashing also required sealing overlapping ends.
Watertight end dams are suggested where horizontal flashing terminates.
Flashing generally should extend 8" (200mm) above the bottom of the flashing and be fastened to the backup.
Through wall flashing at the base of the walls should be located 2" or 3" (50 - 75mm) above finished grade.
Any cavity space below the flashing at the wall base should be completely filled with mortar.
When flashing is placed over a brick, block, or concrete wall adjacent to habitable rooms, a thin bed of mortar or a comparable mastic must be spread onto the brick, block, or concrete walls before the flashing is set in place.
Flashing should be noncorrosive and nonstaining. Copper and galvanized steel may stain adjacent masonry. Copper and stainless steel require a protective material when they are placed next to a steel angle.
Impregnated felt, polyethylene, aluminum or lead should not be used as flashing.
Special Installation Considerations Brick industry standards require the flashing to project 1/4” (5mm) past the face of the brick. For aesthetic reasons, this is normally unacceptable to brick users. The following are alternative details.
For commercial buildings with horizontal control joints, the flashing may stop at the brick face, or 1/8” (3mm) back from the face. An alternative is to wrap the flashing around the angle toe, provide a 100% solid brick below the shelf angle and a moisture resistant sealant in the joint. A third choice is to place the flashing in the mortar joint above the first brick, hold the flashing back 1/2” (12 mm) from the brick face and cover the shelf angle with a self adhering flashing.
For commercial and residential buildings with sills or lintels over openings, the flashing can stop 1/2” to 3/4” (12-19) back from the brick face. Fill the core holes with mortar and spread sealant on the brick below the flashing before it is placed.
Rubber versus Composite Flashing Rubber flashing should normally be neoprene, however, PVC may also be used. For commercial buildings, 50 to 60 mil thickness is suggested. For residential buildings, 30 mil thickness is suggested. Composite flashing is typically made with copper or lead material, covered by bitumen or kraft paper. This cover protects the metal from corrosion, if it is placed in contact with other metals, such as steel lintel.
Rubber flashing is easier to bend, mold, and seal at corners and dams than composite flashing. When flashing needs to span across a cavity, composite flashing is more effective, since rubber flashing will sag and eventually tear from sustained weight. If anchor needs to penetrate the flashing, a thick rubber flashing will seal better around the anchor than composite flashing.
