Cold-formed steel purlins are commonly used in the construction of industrial buildings. The roof sheeting increases the strength of the attached purlin to a considerable extent by providing lateral and rotational restraints. Further, the rotational restraint plays an important role on the buckling behaviour of the attached purlin. There is a need for a design method that accurately predicts the rotational restraint without experimental tests. Addressing this problem, in this research work, a non-linear finite element model is developed to estimate the rotational restraint provided by the first and second generation trapezoidal sheeting to the attached purlin. This model is applicable to trough-fixed and crest-fixed single skin purlin-sheeting systems commonly employed in steel roofs. The performance of the finite element model is validated by conducting experimental tests and found to be in good agreement. The factors influencing the rotational restraint can be investigated by using this validated finite element model. It opens the way to the development of a design method for estimating the rotational restraint provided by the sheeting to cold-formed steel purlins. (C) 2006 Elsevier Ltd. All rights reserved.