underlag

Underlag is a term used in several Nordic languages, including Swedish, Norwegian, and Danish, to refer to the material, document, or layer that serves as a basis or foundation for something else. Depending on context, it can denote a physical base such as a substrate or underlayment, or an informational base such as data, sources, or evidence that supports a decision, analysis, or presentation. The English equivalents include substrate, base, foundation, or underlay.

In construction and flooring, underlag describes the base layer placed between the structural floor and the surface finish. Common types include concrete slabs, plywood or OSB subfloors, or moisture barriers. The quality and flatness of the underlag affect the durability and appearance of the finished floor, and building codes often specify tolerances for levelness and moisture content. In civil engineering, a proper underlag is crucial for load distribution and long-term performance.

In planning, research, and cartography, underlag denotes the set of materials that form the basis for a study or map. This can include source documents, measurements, or base maps and datasets. In decision-making contexts, underlag refers to the compiled information used to justify a conclusion or proposal. The term is also common in legal or administrative settings to describe evidence or documentation that supports a claim or recommendation.

Outside technical contexts, underlag is used more generally to mean the groundwork for an argument or decision and may refer to evidence and supporting materials. Etymologically, it combines under- and lag (layer) and has cognates in related Scandinavian languages. See also substrate, base layer, and datum.