What is the minimum vertical size of the attachment flange of weep screed that is placed on the foundation wall prior to the attachment of exterior lath?

The minimum vertical size of the attachment flange of weep screed that is required to be placed on the foundation wall before the installation of exterior lath is indeed 3-1/2 inches. This measurement is specified in the building codes to ensure proper moisture management and to maintain the effectiveness of the drainage system behind the exterior wall finishes.

Weep screeds serve as a critical component in the water management system of a building's exterior wall. The 3-1/2 inch height allows for adequate space to facilitate the flow of moisture away from the wall assembly, helping to prevent water accumulation that could cause damage or deterioration. The specified height also provides sufficient support for the attachment of lath and ensures that water is channeled effectively without impairing the structural integrity of the wall.

Other options present measurements that do not meet the standard requirements. A smaller flange would fail to provide the necessary drainage and moisture diversion, while a larger flange, although it may seem beneficial, does not represent the minimum standard set forth in construction codes. It’s important for contractors and builders to adhere strictly to these minimum dimensions to ensure compliance with regulations and the longevity of the building's exterior.