Considering the urgent call to tackle climate change, reducing greenhouse gas emissions from the built environment becomes a priority. Slabs in multi-family houses are responsible for a high share of building’s life carbon emissions due to their intrinsic multi-functional nature and high quantity of materials. This research evaluates the impact of the different functional layers within a slab component, compares alternative materials with regards to the functional requirements, and assesses promising solutions in the context of element-based carbon budgets. Life cycle assessment, following established standards, is applied to a representative library of slab components. Results reveal that material choices for the structural layer significantly influence the environmental impact, with wood structure exhibiting five times lower carbon emissions compared to a traditional concrete slab and meeting the most stringent carbon budgets for the structural layer. The screed layer is identified as a significant contributor to the overall impact, holding an important relationship between its thickness and mass and the level of acoustic insulation. Only limited options are available to replace the cement-based screed in its functionality and although the acoustic performance and thickness hold a non-linear relationship, further studies are needed to confidently replace this layer with alternative materials.