Grade Plane, Areaways, and Window Wells

[Harrison Staab]

When calculating Grade Plane (as defined by IBC 2015 Chapter 2), should one take into account things like areaways, light wells, window wells, or exterior stairwells?

Grade Plane. A reference plane representing the average of finished ground level adjoining the building at exterior walls. Where the finished ground level slopes away from the exterior walls, the reference plane shall be established by the lowest points within the area between the building and the lot line or, where the lot line is more than 6 feet from the building, between the building and a point 6 feet from the building.
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I've been unable to find any commentary addressing this. The definition of Areaway is "a subsurface space adjacent to a building open at the top or protected by a grating or guard." This suggests to me that the retaining wall of an areaway (or perhaps a window well, which is not a defined term) is not considered part of the building's exterior walls. If that is the case, then it seems one should take the finished level inside the areaway, not the grade adjacent to the retaining wall of the areaway, when calculating grade plane.

One recent jurisdiction I designed in provided commentary in which they disregard depressions like light wells, depressed driveways, exterior stairwells for purposes of calculating grade plane - at least for zoning building height purposes.

It's perhaps a bit of an odd or nitpicky question, but when one's building is nearing the building height limits, it seems an important one to be sure of in case it comes up.

See attached sketch.

 

[Mr. Inspector]

Interesting question. I think the important thing is where the fireman and their equipment will be when fighting a fire. I don't think they would be standing in any window wells or stairway wells but they can be in a lowered driveway.

 

[RLGA]

I agree that window wells and other areaways should not be considered when determining the grade plane.

 

[Yikes]

Side topic: years ago the Los Angeles zoning code said height was determined by the elevations at the 4 corners of the building. Then some smart*ss developer built a project that had built-in 6' tall built-in planters at each building corner, effectively giving himself an extra story of height. The city has since issued a very detailed explanation of how to calculate height. The limit the size of window wells as part of this calculation.

 

[Harrison Staab]

@Yikes I've seen that LADBS bulletin while working through another project and was the "other jurisdiction" to which I was referring.

 

[sergoodo]

Exiting at the "grade" diagrammed...not sure

 

[Builder Bob]

I beleive the window wells would be a mute point since they are required to have guards installed over them (fall protection)