Nature Communications modelling of whether global steel and cement supply can expand at the rates required by standard development scenarios while remaining within a 1.5°C-compatible carbon budget. The paper finds that feasible low-carbon supply trajectories for both materials fall short of projected demand under conventional growth assumptions, creating a physical constraint that neither demand management nor technological optimism can fully close within the relevant timeframe. For CCS infrastructure planning, the implication is direct: the materials needed to build decarbonisation assets face the same supply pressure as everything else, and assuming unconstrained material availability in project cost modelling is a planning error that will surface as construction cost overruns.