The paper addresses two significant and growing trends: knowledge work and population ageing. The population pyramid inversion brings important changes for society as a whole. These changes are associated with the inclusion of older persons in the workforce for knowledge work, which represents a challenge for adapting the work environment to meet all workers' needs. In order to approach a more universal design of the work environment system, industrial designers need support from user-sensitive inclusive design studies. Moreover, there are plenty of guidelines and tools containing relevant information. However, there is the need to develop more appropriate tools oriented to industrial designers and that cover the initial phase of the design process. A study about and with users and designers have driven the research outcomes and direction. Through an iterative process, various prototypes versions have been developed through research and designers' feedback. A range of contents and a theoretical framework, namely UCAP, have been developed in order to implement them in this inclusive workstation design guidance tool. This study provides an overview of how knowledge work is affected by the ageing of the population, the role of designers in helping to create inclusive workstations, and the need for developing a new tool to aid designers in this endeavour. A theoretical framework intended for use in the development of the inclusive workstation design guidance tool is proposed and developed. As a result, this study provides one step towards the universal design of the products and environments found in knowledge work for the benefit of not only designers but consumers, makers and buyers of such products, all of whom can benefit from these outcomes.