This report is a publication of the European Network COST FP1402 Basis of Structural Timber Design - from research to standards. The aim of the Action was to overcome the gap between broadly available scientific results and the specific information needed by designers, industry, authorities and code committees, providing transfer for practical application in timber design and innovation. This report represents the results of the activities performed in Working Group 1, Basis of Design. The most important task of Working Group 1 was the defragmentation and harmonization of techniques and methods that are necessary to prove the reliable, safe and economic application of timber materials or products in the construction industry. This report is structured into five parts. At first general principles regarding the design formats are addressed (Part I). Afterwards timber specific aspects regarding code calibration (Part II) and serviceability (Part III) are summarized. In Part IV other demanding issues for the implementation into Eurocode 5 are addressed. Here also summaries of joint activities with other working groups on cross laminated timber and timber connections are presented. The report concludes with a guideline for data analysis (Part V).