Life-cycle assessment (LCA) is an established methodology that can provide decision-makers with comprehensive data on the environmental impacts of products and processes during the entire life cycle. However, the literature on building LCAs consists of highly varying results between the studies, even when the assessed buildings are very similar. This makes it doubtful if LCA can actually produce reliable data for supporting policy-making in the building sector. However, no prior reviews looking into this issue in the building sector exist. This study includes an extensive literature review of LCA studies on the pre-use phase of buildings. The purpose of this study is to analyze the variation between the results of different studies and find out whether the differences can be explained by the contextual differences or if it is actually the methodological choices that cause the extremely high variation. We present 116 cases from 47 scientific articles and reports that used process LCA, input–output (IO) LCA or hybrid LCA to study the construction-phase GHG emissions of buildings. The results of the reviewed studies vary between 0.03 and 2.00 tons of GHG emissions per gross area. The lowest was assessed with process LCA and highest with IO LCA, and in general the lower end was found to be dominated by process LCA studies and the higher end by IO LCA studies, hybrid LCAs being placed in between. In general, it is the methodological issues and subjective choices of the LCA practitioner that cause the vast majority of the huge variance in the results. It thus seems that currently the published building LCAs do not offer solid background information for policy-making without deep understanding of the premises of a certain study and good methodological knowledge.