ISO 4355:2013 specifies methods for the determination of snow load on roofs.It can serve as a basis for the development of national codes for the determination of snow load on roofs.National codes should supply statistical data of the snow load on ground in the form of zone maps, tables, or formulae.The shape coefficients presented in ISO 4355:2013 are prepared for design application, and can thus be directly adopted for use in national codes, unless justification for other values is available.For determining the snow loads on roofs of unusual shapes or shapes not covered by ISO 4355:2013 or in national standards, it is advised that special studies be undertaken. These can include testing of scale models in a wind tunnel or water flume, especially equipped for reproducing accumulation phenomena, and should include methods of accounting for the local meteorological statistics. Examples of numerical methods, scale model studies, and accompanying statistical analysis methods are described in ISO 4355:2013 (Annex G).The annexes of ISO 4355:2013 describing methods for determining the characteristic snow load on the ground, exposure coefficient, thermal coefficient, and loads on snow fences are for information only as a consequence of the limited amount of documentation and available scientific results.In some regions, single winters with unusual weather conditions can cause severe load conditions not taken into account by ISO 4355:2013.Specification of standard procedures and instrumentation for measurements is not dealt with in ISo 4355:2013.