Glossary Term Defined

A line that constitutes the perimeter of the Interior Gross Area (IGA) of a floor level. It determines the value of the interior gross area of a floor level and is located at the innermost occurrence of any of the following IGA boundary conditions:

• Vertical exterior enclosure utilizes the concept of dominant portion to establish the IGA boundary for this condition.
• Public pedestrian thoroughfare replaces the concept of ground level street frontage in the previous standard. The IGA boundary is determined by applying the concepts of exterior enclosure and enclosure limit.
• External circulation is a common condition in temperate climates where the primary circulation for the building occurs outside the exterior enclosure. When this condition exists the IGA boundary is determined as follows:

 At above-grade level, the edge of the walking surface, limited to the width required for access to and egress from occupant suites, typically five to six feet.

At grade level, a vertical projection of the edge floor level or roof above, and/or limited to the width required for access to and egress from occupant suites, typically five to six feet.

• Non-vertical exterior enclosures is a condition that occurs for either the entire exterior enclosures or a segment of the exterior enclosures between floors. When encountered, the IGA boundary is located at the intersection where the finished surface of the floor meets the inside finished surface of the exterior enclosure.
• No dominant portion occurs when the exterior enclosures have three or more finished surfaces, none of which constitute 50% or more of the finished floor-to-ceiling dimension. The IGA boundary is located at the intersection where the finished surface of the floor meets the inside finished surface of the exterior enclosure.
• Unprotected exterior opening most frequently occurs at a vehicle entry point like a loading dock. The IGA boundary is located as the outermost horizontal line of (a) a line connecting the outermost surfaces of the exterior faces of the exterior building columns or (b) a line across the opening that connects the outside face of the adjacent exterior enclosure.
• IGA adjacent to a void with a full or partial wall. Since a void is not part of the interior gross area and occurs inside the exterior enclosures the separation might not require a full enclosure. However, the IGA boundary should be determined using the similar conditions used for exterior enclosures, namely condition ID #1, #4, and #5.
• IGA adjacent to a void without a wall or enclosure creates an IGA boundary at the edge of the floor surface between the void and the interior gross area.
• Ownership change inside the building or connector (except at vault space) forms its IGA boundary at the property line that establishes the change in ownership. Vault space is excluded from this condition, since utility and similar vaults typically occur on public property and are an essential part of the building. Ownership changes where a lease or license combines rights of use for the benefit of the building are also excluded.