The existing masonry and reinforced concrete built heritage is generally aged and inadequate to the seismic and energetic performances required nowadays due to natural hazards and climate change. Innovative techniques deserve strong interest, especially if include multi-task approaches. Eco-friendly and eco-sustainable materials and systems are preferred. Therefore, timber-based elements represent an optimal option able to satisfy seismic and climatic requirements contemporarily, thanks to the intrinsic physical and mechanical properties of wood, among them lightness, high strength-to-weight ratios and natural sustainability, as well as easiness of production and realization along with favourable energetic performances. For these prerogatives, in recent years, timber has become a trend worldwide in the construction sector. New techniques based on the use of timber-to-steel or all-timber solutions are gaining popularity for restoring existing structures belonging to the historical, artistic and also productive built heritage.

In this framework, the paper presents a state of the art on the main researches and applications concerning timber-based elements for the retrofitting of existing buildings. Then a structural typological classification is proposed. In particular, two macro-categories of interventions, global and local, are defined: the first includes additional timber eso- and endo-skeletons applied to the existing structures, while the second concerns the strengthening of the single structural or non-structural elements. Finally, the proposed classification emphasizes pros and cons of each intervention in the framework on seismic and energetic integrated design.