Concrete is the world’s most used construction material. There are significant challenges with the decarbonisation of concrete, particularly cement, due to the release of carbon dioxide emissions during clinker production. Therefore, strategies to reduce embodied carbon in concrete buildings should aim to focus on material efficiency efforts first. Existing relationships between concrete and embodied carbon, such as increased concrete strength, increasing global warming potential (GWP), increased span length increasing GWP, and taller buildings generally having higher carbon have been investigated. However, some relationships are yet to be explored. These include the relationship of form and associated structural layouts to embodied carbon. One of the challenges of conducting embodied carbon assessments is the selection of material embodied carbon coefficients (ECCs). This is particularly true during early-stage design when the specific material selection is still unknown. A common early-stage technique for identifying embodied carbon reduction strategies is identifying carbon hotspots. However, these hotspots can be heavily influenced by the large variation in environmental product declarations (EPD) across manufacturers and differing product specifications. Without quantifying this uncertainty due to material ECC uncertainty, selecting the most likely lowest-impact design option is challenging. The most common approach for uncertainty propagation is to use Monte Carlo (MC) simulations. This propagation provides results as a distribution instead of a single, deterministic result. It is simple to compare single-value results to demonstrate the difference between design options and select the lowest-impact alternative. However, using uncertainty statistical methods to compare structural frame designs against each other and also against industry benchmarks is yet to be investigated. Therefore, comparative statistical methods are evaluated for their suitability in early-stage decision-making and, specifically, structural frame design comparisons. This thesis introduces a newly-proposed methodology that propagates uncertainties in material quantities and ECCs during early-design comparisons. The methodology incorporates a novel ranking step to identify key contributing materials, streamlining assessments by reducing time and focusing on material hotspots. A new uncertainty characterisation of construction materials is introduced, utilising statistical parameters from an industry material ECC database. The thesis later integrates quantity uncertainty by design stage with material ECC uncertainty for early-stage structural EC assessments, capturing incompleteness and variation due to quantity take-off methods and early-stage estimations. Additionally, the thesis introduces a new parametric tool for early-stage concrete frame designs. This tool incorporates form definition (for seven-shaped buildings), followed by a layout derivation for all possible solutions within a span range. Next, a C# script within the tool conducts structural RC design for multiple slab types, and finally, product-stage embodied carbon calculations with uncertainty are presented. An investigation into the influence of architectural form on structural frame layouts and resulting embodied carbon was conducted, considering seven equally-sized shaped forms for two plot sizes. In combining the uncertainty procedure and parametric form design tool, comparative statistical methods for evaluating uncertain results are tested for the first time in a building EC context. Lastly, the thesis concludes by proposing a novel application for comparing structural EC results against the SCORS rating system. By including uncertainty in early-stage building EC assessments, this thesis enables engineers to conduct more reliable and fair comparative EC studies. Relying on average material ECCs (with uncertainty) through early design stages also benefits practitioners by prioritising EC savings through demand reduction and material efficiency without relying on low-carbon products.