Where is the "ground"?

[nealderidder]

When it comes to determining whether or not a story is "above grade" it's pretty straightforward at first... Determine your average ground level adjoining the exterior building walls (go out 6' looking for the lowest point) and you've got your grade plane. So that makes sense to me. On the attached I calculated a grade plane of 100'. It's obvious from the sketch that levels 1,2,3 are all above grade plane.

Level B1's determination is by the following criteria:

• Is the next floor above B1 (1FL) more than 6' above grade plane? No
• Is the next floor above B1 (1FL) more than 12' above the finished ground level at any point? That's my question.

On the attached you see a section showing a lightwell on the left and a driveway on the right. B1 is an enclosed parking garage. Where would you locate finished ground level on the left hand side (or right for that matter)? Should it be measured at point "A" or point "B"? "B" is a paved area and "A" is the existing grade elevation. We're excavating for that lightwell. So where is the "ground"?

Would love to hear your thoughts.

Neal

 

[Mech]

I say it is the level immediately adjacent to the building, which is point B for the left side of the building. That's my 2 cents.

 

[Mr. Inspector]

I would say B

2015 IBC
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 (1829 mm) from
the building, between the building and a point 6 feet (1829
mm) from the building.