INTRODUCTION Timber, frequently associated with masonry and stone, is the material most uninterruptedly used by mankind. Thus, the heritage of timber structures is immense and several and wideranging structural typologies and functions are assigned to these structures. Timber is also one of the most used materials in specific typologies of roofs and floors (churches, bridge building, pools, etc.) in Portugal. In construction Glulam is used for its strength and character building versatility. It can be produced in individual shapes – straight or curved – large or small, providing to the building a light and gentle touch. Modern Glulam technique combined with the durability of wood makes Glulam a highly versatile construction material with unique qualities. Complex timber structures, such as those belonging to the roofs of large Glulam structures, are often not easy to understand in a expedite way. This complexity makes the field of Glulam structures not only a challenge but a field much in need of modern research. This paper presents some of the Portuguese experience in this field, showing how architectural solutions can be supported by an extensive knowledge about the constituent material from which the structure was made, both from the mechanical point of view and from the physical ABSTRACT: Timber is one of the most used materials in specific typologies of roofs and floors (churches, play grounds, bridge building, pools, etc.) in Portugal. The geometry is defined by elements that occupy a limited and well defined part of the tri-dimensional space, with a clear evidence of the hierarchy of the components. Timber elements are often visible, which allows easier conservation, identification of the wood species, characterization of details and evaluation of deterioration. In construction Glulam is used for its strength and character building versatility. It can be produced in individual shapes – straight or curved – large or small, providing to the building a light and gentle touch. Modern Glulam technique combined with the durability of wood makes Glulam a highly versatile construction material with unique qualities. Complex timber structures, such as those belonging to the roofs of large Glulam structures, are often not easy to understand in a expedite way. This complexity makes the field of Glulam structures not only a challenge but a field much in need of modern research. The objective of this paper is to present some of the Portuguese experience in this field, showing how architectural solutions can be supported by an extensive knowledge about the constituent material from which the structure was made, both from the mechanical point of view and from the physical point of view. A number of case studies will be presented to illustrate common design problems and solutions, as well as the possibilities and limitations of this material.