Base Building

The base building is what the landlord owns and maintains: the structure, roof, exterior walls, elevators, main lobbies, and the base utility lines brought to your space. Everything inside your four walls that makes it usable as an office is the build-out, and that is where tenant and landlord responsibilities get negotiated.

The catch is that base building means different things in different deals. One landlord delivers a space with HVAC trunk lines, a finished ceiling grid, and distributed power. Another hands you four concrete walls and a single utility stub. Both can be called shell, so the only thing that protects you is a written delivery condition that spells out exactly what you are getting.

Shell is a slippery word, and landlords use it loosely. Two spaces described the same way can carry very different hidden costs once you start building. Before you compare rents, compare what each landlord actually delivers at the base building level, because that gap often matters more than a dollar or two in rent.

A medical group tours two Oak Brook suites both marketed as shell. The first already has a rooftop HVAC unit, a sprinkler main, and electrical service to the suite. The second has none of it. Same label, but the second will cost 40,000 to 60,000 dollars more to make usable, which changes which deal is actually cheaper.