This paper presents the basis for changing the current test and evaluation procedure used to establish bracing ratings. This is known as the BRANZ P21 test method and is used to obtain the bracing ratings of timber framed wall systems for houses, and other low-rise structures, to meet the wind and seismic demand stipulated in the light timber framing standard, NZS 3604:1999. The demand seismic loads in NZS 3604 were based on the loadings specified in the New Zealand loadings standard, NZS 4203:1992. This paper proposes a revised P21 test seismic evaluation (called EM3) so that houses constructed to NZS3604 do not exceed their wall deformation capacity when analysed against a suite of earthquake records compatible with NZS 4203:1992.