When installing flashing in a brick veneer system over a metal stud backup, should I place the top edge of the flashing behind the gypsum sheathing or simply behind the building paper?
If the flashing is placed behind the gypsum sheathing, holes drilled to connect the sheathing to the bottom track will penetrate this flashing and make it ineffective above that point. Also, if water ever builds up to this level, it will saturate the gypsum sheathing at the bottom. The flashing should extend up the outside surface of the gypsum sheathing and be covered with No. 15 asphalt felt building paper. That way, the water is shed by the felt onto the flashing. I recommend using building paper no matter where the building is located. It will protect the surface of the gypsum sheathing from any water that might cross the cavity over mortar bridges, ties, or other means. If it is properly installed over the surface of the gypsum sheathing and under the building paper, the flashing will not be penetrated.