<p>Recycling post-consumer cellulose waste for use in construction materials has largely been limited to board-type composite materials. While the wood-panel market is dominated by OSB and MDF, there is limited research concerning structural boards produced directly from recycled paper waste through simple processing methods. This work examines the potential to produce rigid polyurethane–cellulose composite boards using ground waste newspapers as a filler material without a catalyst. Composite boards containing 10–50 wt.% cellulose were manufactured by hot pressing and evaluated for tensile and compressive strengths, Charpy impact testing, thermogravimetric analysis, dynamic mechanical analysis, and water vapour permeability. The modulus of elasticity increased nearly three times from 10% cellulose content to 50% cellulose content due to the increased cellulose content. The maximum compressive strength was achieved at 30% cellulose content. Impact strength was not significantly impacted by filler content, resulting in consistent values for all compositions. Thermogravimetric analysis indicated that, with increasing cellulose fraction, thermal stability improved (e.g., the peak decomposition temperature (PDT) increased). Dynamic mechanical analysis results confirmed that, for boards with high cellulose content, stiffness and energy dissipation increased with each incremental increase in cellulose content. The results of the study indicate that paper recycling waste can be processed into a mechanically stable material, Polyurethane-Cellulose Boards, for use in many non-load-bearing applications within the construction sector. Using these boards represents a viable and scalable means of converting cellulose waste into a usable product in the construction industry.</p>