Recently unclassified boards with varying composition and more notably with ambiguous thermal properties are being used in buildings. The fire performance of Light gauge Steel Frame (LSF) wall systems mainly depends on the protective plasterboard linings used and thus fire safety concerns are being raised. Therefore this study was aimed at setting minimum standards for fire-resistant grade plasterboards used in LSF wall applications based on material characterization, thermo-physical properties and finite element heat transfer modelling. The most commonly used fire protective board, gypsum plasterboard was used to address this critical issue. Thermo-physical properties of three gypsum plasterboards manufactured in Australia were measured and compared in relation to their chemical composition in the first phase of the study. Fire resistance levels (FRLs) of LSF wall systems lined with these three plasterboards were determined using 3-D FE heat transfer models of LSF wall systems developed and validated in this study. The paper proposes a “k-factor” based on thermo-physical properties and thickness of plasterboard, capable of giving an overall measure of the fire performance of plasterboard lined LSF walls. Standard k-factor profiles were established for non-load bearing LSF wall systems with FRLs of 60, 120, 180 and 240 min by considering the correlation between the time-temperature profiles from numerical analyses and calculated k-factors. These proposed standard k-factor profiles give an overall measure of the fire performance of plasterboards. This paper presents the details of this study and the results.