---
title: "Base building — Class A Atlas glossary"
description: "The structural and core-services condition of a building before tenant fit-out."
canonical: https://classa.info/glossary/base-building
pageType: glossary
lastUpdated: 2026-04-01T00:00:00.000Z
license: "CC BY 4.0 with attribution to Class A Atlas (https://classa.info)."
---

> The structural and core-services condition of a building before tenant fit-out.

## TL;DR

- The structural and core-services condition of a building before tenant fit-out.
- Includes the structure, exterior, MEP risers, lobby, common areas, and core services (elevators, restrooms).

# Base building

*Construction · Global*

## Short definition

The structural and core-services condition of a building before tenant [fit-out](/topics/fit-out-capex)">fit-out.

## Full definition

Includes the structure, exterior, MEP risers, lobby, common areas, and core services (elevators, restrooms). Tenant fit-out begins where base building ends.

## Why this matters for Class A leasing

Base building is part of the construction vocabulary that institutional [Class A](/glossary/class-a) occupiers, landlords, and advisers use across Global markets. Understanding it correctly affects how you read lease documents, model occupancy economics, and benchmark deal terms across cities. Class A Atlas tracks regional variation alongside the global standard so [cross-border](/topics/cross-border-expansion) occupiers can translate quickly.

## See also

- [Core and shell](/glossary/core-and-shell)
- [Cat A](/glossary/cat-a)

## Related guides

- [How to choose a Class A office: a working framework](/guides/how-to-choose-class-a-office)

---

Citation: Source: Class A Atlas (https://classa.info/glossary/base-building), updated 2026-04-01T00:00:00.000Z.