The televised devastation of the Loma Prieta earthquake in October 1989 renewed concerns about the vulnerability of unreinforced masonry (URM) buildings. Recognizing the need to retrofit these old URM structures, Los Angeles established in 1981 what is now known as Division 88 of its building code. The code requires some 8,000 URM buildings to be retrofitted, vacated, or demolished. Experience with thousands of URM buildings has identified four major aspects of seismic retrofitting: anchoring walls to diaphragms; wall repair and strengthening; diaphragm repair and strengthening; and adding shear elements. ANCHORING WALLS TO DIAPHRAGMS Anchoring systems mechanically connect walls and diaphragms and limit destructive wall deflection. Most anchoring systems combine bolts passed through or grouted into the walls and a means of attachment to the diaphragms. WALL REPAIR AND STRENGTHENING Anchoring works only if the walls can absorb or transfer seismic energy from the diaphragms. To meet this demand, deteriorated or damaged masonry must be repaired. Often walls must be strengthened. DIAPHRAGM REPAIR AND STRENGTHENING To transfer seismic forces from walls perpendicular to the forces to walls parallel to them, diaphragms must be strong and flexible. Just bringing framing members up to standard is an important part of this job. ADDING SHEAR ELEMENTS When the design of the original building doesn't provide adequate shear capacity, additional shear-resisting elements are required. In the roof, a truss or section of rafters can be sheathed with plywood on one or both sides to create a shear structure which must be secured to the walls-preferably the bearing walls.