Good english translation for construction term "Obra Negra"

I think that rough construction is the expression you are looking for:

• The rough construction means the building of the load-bearing structure of the building – its frame. The process includes foundation (formwork, rebar and pouring of the foundations), the construction of the walls above the ground, slabs, reinforced concrete floors and load bearing walls (anti-earthquake washers), columns, beams, brickwork, stairs, staircase landings, chimneys, shafts, lift shafts, etc. (including formwork, rebar and pouring of concrete for each of the enumerated elements) and roofing.

(www.chobanovstoyanov.com)

Note also "Rough In":

• As applied to home building and remodeling, to rough in means to lay out the basic lines without making the final connections. Walls are still open and the drywall is not yet installed.

• The absence of wall and floor coverings allows for easier modification if the rough in does not pass inspection or if the homeowner makes a change order to alter the project.

(www.thespruce.com)