Son of the architect Modest Fossas, he was an artist who adapted to the trends at any particular time, which meant that his production was extremely diverse.

In 1900 he became the architect of the Ornamentation Section of Barcelona City Council and gradually received various appointments, such as chief architect of the Technical Section of the Property Development Department - during which period he designed residential buildings in various neighbourhoods of Barcelona - and municipal architect of Malgrat de Mar, El Masnou and Arenys de Mar.

His buildings in the first decade of the 20th century, such as Casa Josefa Villanueva (1904-1909; València, 312) and Casa Marià Pau (1907; Roger de Llúria, 129), show a certain influence by A. Gaudí and J. Rubió i Bellver. In 1915 he abandoned the Modernista style and designed buildings in the monumentalist style, such as that of the former Companyia Transmediterrània (1917; Via Laietana, 2; now offices of the Ministry of Justice).