A series of flexural tests were conducted on 18 structural insulated header panels with timber flanges and Oriented Strand Board (OSB) webs to predict their behavior when subject to gravity loading when used in residential and low rise non-residential buildings. The experiments were designed and performed to test full-scale Structural Insulated Panels (SIPs) headers for exterior or interior wall residential construction. The structural adequacy of the header panels of various sizes is investigated in order to meet both strength and serviceability limit-state design requirements per Canadian Standards for timber design. Strength requirements included flexure and shear, while serviceability check included limiting deflection under operating conditions. Results from experimental testing were used to draw conclusions with respect to the structural qualifications for these SIP headers to be "as good as" the structural capacity of conventional wood-frame buildings.