The architectural heritage of the city of Barcelona in its older neighbourhoods of historic importance consists largely of buildings whose roof is formed by the Catalan vault. This roof type consists of vaults built in ceramic blocks, supported by unidirectional beams, wherein the space between the vaults and the upper floor is filled with ceramic material and/or construction waste. Over time, these structures presented problems of thermal and acoustic insulation, as well as of load distribution, causing the detachment of the upper floor tiles in buildings with multiple floors. In order to solve this problem, a lightweight self-compacting concrete reinforced with plastic fibres was developed to replace the existing lightweight material. The objective of this paper is to present the experimental results obtained during the pumping of the lightweight aggregate concrete produced. Expanded clay in the dry condition was used. A density close to 1,600 kg/m3 was achieved, as well as a compressive strength higher than 17 MPa at 28 days. Details of the application of this material in the rehabilitation of the historic building dating from 1905, the Gaudí House Museum in Barcelona, which was the residence of the architect Antoni Gaudí during 1906-1925, is also given.