This European Standard constitutes a frame standard for the design of timber stairs as well as wood and wood-based components used in stairs by calculation methods. Some calculation methods can be derived from testing results, for example CEN/TS 15680. This document specifies the design and the requirements for materials and components to be used in these calculation methods. It may be complemented by national application documents based on this European Standard. This European Standard applies to coated and uncoated components. This document covers load-bearing components such as strings, treads, risers, posts and guardrails. Requirements for a timber stair are defined in the product standard, EN 15644. This document does not cover stairs that contribute to the overall stability of the works or the strength of the structure. This European Standard is valid for the verification of mechanical performance characteristics, usability and load-bearing capacity and their related durability. Other requirements, e. g. requirements for acoustic properties, are not covered by this European Standard. For the design, calculation and determination of not solely resting actions, additional requirements need to be taken into account (to be checked). For the dimensioning with special reference to resistance to fire and earthquake/seismic action, additional requirements may be taken into account. Without further verification, the methods in this European Standard are valid for different types of stair structures and their components, as illustrated in Figure 1: a) Stair with closed string and riser b) Stair with closed string without riser c) Stair with cut strings and riser d) Stair with cut strings without riser e) Combination of stairs with closed string and cut string with or without riser Figure 1 - Types of stair structures and their components.