definition
strict definition
shell construction
A contractor that builds a building's structural framework, whether of concrete, steel, or another material.
A shell construction company is the contractor which builds the framework of a building. Depending on the primary material of a building, it may be called the concrete contractor, steel contractor, etc.
The constructed product is the building's framework. Concrete and steel contractor are material-based descriptions of this work, rather than different requirements for the overall shell-construction activity.
Interior fit-out constructs rooms, ceilings, and partitions inside the building. The shell contractor's work concerns the framework, while a steel fabricator manufactures structural members that a contractor may use.