Until the late 1960s, Teixeira Duarte's activity was exclusively focused on the fields of Geotechnics and Foundation Engineering. However, it was gradually extended to other fields of Construction, which, in the remodelling of the Company's by-laws in 1961, materialised in the alteration of its corporate object: "execution of studies and engineering works, especially geological surveys, groundwater abstraction, soil consolidation and waterproofing, foundations and constructions of all kinds.".

Throughout the 1960s the company grew, highlighting works such as the foundations and structures of the Aviz Building and the Sheraton Hotel in Lisbon, which were carried out by Teixeira Duarte, with design by the engineer Edgar Cardoso, proving the Company's execution capacity and reinforcing its image in the market.

In 1966, Teixeira Duarte moved its headquarters to Avenida da República, no. 42, in Lisbon - where it would remain until 1993 - and created, in 1967, a new construction yard, larger and with better conditions, in Santa Iria.