3 rd International Conference on PROTECTION OF HISTORICAL CONSTRUCTIONS Lisbon, Portugal, 12 – 15 July, 2017 THE USE OF A CFRP REINFORCED RENDER IN THE SEISMIC STRENGTHENING OF OLD BUILDINGS João Alexandre Guerreiro*, Filipe Dourado** and José Paulo *** *CERIS, Instituto Superior Técnico - Universidade de Lisboa e-mail: jg@civil.ist.utl.pt ** S&P Clever Reinforcement Iberica e-mail: filipe.dourado@sp-reinforcement.pt *** STAP –Reparação , Consolidação e modificação de Estruturas e-mail: jpcosta@stap.pt Keywords: CFRP reinforced render; seismic strengthening; old building; out-of-plane bending; in- plane bending; Abstract. Testing Pombalina Walls reinforcement with new carbon composite grids. 1 INTRODUCTION Old buildings are commonly composed by loadbearing masonry walls and wooden floors and roofs. Those type of construction has undeniable low seismic reliability that is aroused from a group of inefficient behaviours, extensively studied in a recent past [1-6]. Those studies showed that to improve the old building seismic performance the retrofitting strategy must be guided for the reduction of the effects of specific behaviour malfunctions. The most recognized are the out-of-plane bending and the connection ineffectiveness between structural elements, while in-plane bending and the shear mechanisms are also often a concern. Structural retrofitting of an old building has nowadays the awareness that an efficient seismic response can only be established when the old building structural identity is respected. It can be stated that it is unworthy to develop reinforcing interventions that counteract the natural behaviour of an old building, removing from the scope of possible strengthening techniques the most widely used for steel and concrete structures. Likewise, the development of efficient strengthening techniques can only be achieved when the structural particularities of vertical structural elements composed by masonry and horizontal structural elements composed by wood are a given knowledge. The development of the strengthening technique presented in this paper had the same guideline. The main concern for its development was the respect for the potential intervened structure, rather than the mechanical enhancements that its features could achieve. The basic idea for this technique was the addition of a structural layer to the masonry wall that could enable significant out-of-plane displacements without significant mechanical differences regarding the non-intervened masonry wall. Therefore the added material needed to be compatible with the masonry element, mechanically, physically and chemically. One of the main problems within the reinforcement development was that the needed compatibility was roughly against the masonry basic mechanical needs for out-of-plane