I can help. What jurisdiction are you located in?
There are generally two height limits for a residential building. one is for the Building Code and one is for Local Zoning Requirements.
Is your limit related to a Building Department requirement or a Planning/Zoning Department requirement?
Yes they do.
The California Building Code is a mandate that all jurisdictions in the State have to follow.
Planning Codes are different in every City and every County area.
What City are you located in?
I have found the section in the San Francisco Planning Code that explains how to measure the height of your structure.
Take a look at the following link in Section 260: Height Limit Measurement
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Yes, can I get with you tomorrow?
So on the front elevation of your house, grade will be considered the top of curb level, since I assume the front of your house is within 10' of the property line. The C/L of your house will be established by splitting your house in 1/2 with a line that extends out perpendicular to the curb. Follow that line till it intersects your front elevation and take the height from the top of curb to the top of your roof at the C/L.
Here is a link to a standard method used in the Building code to measure the average grade plane along a house on a variable slope.
I hope this helps.