There are no connections between the roof diaphragm and the walls that are capable of transferring in-plane forces from roof to wall and restraining outward displacements of walls.

RWCN_-_FEMA172_1

Example of connections of a steel deck diaphragm to a concrete or masonry wall, that may be inadequate (adapted from FEMA 172, 1992)

RWCN_New Zealand_ClarkW_1

An inadequate connection of a wooden roof to the masonry wall in a building damaged in the 2011 Christchurch, New Zealand earthquake (W. Clark)

RWCN_Loma_Prieta_1989_EERI_1

Out-of-plane collapse of masonry walls at the top floor level in a building due to inadequate roof-wall connection, 1989 Loma Prieta, California earthquake (EERI Reconnaissance Team)

RWCN_Northridge_1994_EERI_1

Out-of-plane collapse of masonry walls in a building damaged in the 1994 Northridge, California earthquake; note floor-wall anchors (EERI Reconnaissance Team)

RWCN_Canada_AdamsJ_1

RWCN_Canada_AdamsJ_2

Roof-wall diaphragm connections between steel trusses (known as Open Web Steel Joists in North America) and masonry walls may be inadequate if support dimensions and attachment are not adequately designed and/or constructed (J. Adams)