FAQ · 4 min read

Does a Sunken Living Room Count as GLA?

Yes — in virtually all cases, a sunken living room counts as GLA. The step down is an interior design feature, not a below-grade condition. Here is the reasoning and what to watch for.

What "above grade" actually means

Under ANSI Z765, a space qualifies as GLA only if it is above grade — meaning the floor level is above the exterior ground level on all sides. The critical measurement is between the floor of the space and the ground outside the building, not between that floor and other interior floors.

A sunken living room steps down 12 to 24 inches from the main floor level. But the main floor of most homes is itself 12 to 36 inches above exterior grade. The sunken portion is still above the outside ground — it just sits lower than the rest of the interior.

This is fundamentally different from a basement, which sits below the exterior ground level. A sunken living room is not a basement — it is a stylistic variation in floor level within the above-grade portion of the home.

The ANSI Z765 grade test

ANSI Z765 defines below-grade area as space where any portion of the floor is below the exterior grade on any side. To determine whether a sunken living room crosses this line:

• Walk outside and observe the ground level around the exterior of the sunken area
• If the sunken floor is still above the outside ground on all sides, it is above grade and counts as GLA
• If the sunken floor drops to or below the exterior ground line on any exterior wall, that portion must be excluded from GLA

In most residential construction, this test is easy to pass. Standard floor-to-grade clearance and typical step-down depths of 12 to 24 inches leave the sunken floor well above exterior grade.

When it gets complicated

The edge case is a home built into a hillside or slope. If the sunken living room is on the downhill side of a sloped lot, it is possible for the sunken floor to be at or below grade on the lower side of the house — even if it is clearly above grade on the uphill side.

ANSI Z765 applies the below-grade test to any exterior wall. If the sunken floor is below grade on even one side, that area is excluded from GLA and reported separately as below-grade finished area.

This is uncommon for sunken living rooms specifically — they tend to appear in ranch-style and contemporary homes on relatively flat lots — but it is worth checking on hillside properties.

How to measure it

From a floor plan perspective, a sunken living room is measured the same as any other room. You trace the perimeter of the space, including the sunken area, at the exterior wall footprint. The step down in floor height does not change the horizontal area.

When using a floor plan image, the sunken living room will appear at the same scale as the rest of the main level. Include it in your GLA perimeter trace normally.

One thing that does not affect GLA: ceiling height over the sunken area. Even if the sunken living room has a double-height ceiling (which it often does in open-plan homes), that space is counted by its floor area footprint, not by the volume of space above it. The ceiling height qualifies the space for GLA (must meet the 7-foot minimum) but does not add to it.

Summary

• A sunken living room almost always counts as GLA
• The interior step-down does not make it below grade — only the relationship to exterior ground matters
• On sloped lots, verify the sunken floor is above the exterior grade on all sides
• Measure it the same as any other above-grade room: by exterior footprint area
• What counts as square footage in a house

Related: Above grade vs below grade · What counts as GLA · Walk-out basement GLA · Open-to-below GLA

Compare: GLA vs Total Square Footage: What Is the Difference? · ANSI Z765 vs BOMA: Square Footage Standards Compared