WRB

In construction terminology this is a common abbreviation for water resistant barrier.  Water resistant barrier can be designated as one of many materials or types of materials that prevent water penetration at the defined envelope building when combined with proper detailing and methods of flashings.  In the past materials commonly used for WRB include D-Felt Paper, Tyvek, Perma-Barrier, etc.  Currently there are many engineered solid and liquid membrane systems used for WRB.