English to Italian Tech/Engineering Construction / Civil Engineering

buongiorno, in un testo che sto traducendo compare l'espressione

1st fix building works

che da quanto dice wikipedia significa:

First fix comprises all the work needed to take a building from foundation to putting plaster on the internal walls. This includes constructing walls, floors and ceilings, and inserting cables for electrical supply and pipes for water supply.

qualcuno mi sa dire come posso tradurla? Opere primarie??? e, in caso di 2nd fix building works, opere secondarie???

Grazie