Urban planning community | #theplannerlife

1. ## Building height

How do you calculate height on a residential home with several different roof heights on a sloping lot? Do you take an average of all the individual roof heights, an average of the grade, a midpoint on the roof between the eave and peak?

Our ordinance says
Building height: The vertical distance measured from the established grade to the highest point of the roof surface for flat roofs, to the deck line of mansard roofs and to the average height between eaves and ridge for gable, hip and gambrel roofs. Where a building is located on sloping terrain, the height may be measured from the average grade.
And then for Average Grade it says
Average grade: The ground elevation established for the purpose of regulating the height of the building. The building grade shall be the level of the ground adjacent to the walls of the building if the finished grade is level. If the ground is not entirely level, the average grade shall be determined by averaging the elevation of the ground for each face of the building. ("Average grade" shall also include "grade.")
I have one architect that wants to use a combination of average grade and average height.

2. don't you use average grade to determine the ground level that you measure the height from? That is how I read the ordinance, so you would use both. The average grade being the low point and the average height being the high point. To determine the average height, I would just take the highest point of the roof and the lowest point and find the mid grade, no need to worry about the rest of the roof line. One easy way to do it is to trace an envelope around the perimeter based on the average grade and the average height. if parts exceed it, you have a height that is not consistent with the code.

This is why building height is better measured from grade to the peak. It eliminates the need to interpret the ordinance. You dont need to worry about grade because if the property is on a slope the design of the home should be such that the roof line follows the grade. It requires the architect to think about the site a little bit more and you get a situation where the impact on the downhill neighbor is reduced. You could also throw in a regulation about max height of exterior wall so that you end up creating more of a building envelope type of regulation.

3. Originally posted by michaelskis
How do you calculate height on a residential home with several different roof heights on a sloping lot? Do you take an average of all the individual roof heights, an average of the grade, a midpoint on the roof between the eave and peak?

Our ordinance says

And then for Average Grade it says

I have one architect that wants to use a combination of average grade and average height.
We measure from the highest roof gable of a multi gabled roof. We measure an average typically between the peak and the eave. However, we do have diagrams for sloping lots and how height is measured from that. Here is the LINK which should help as it is hard to explain, but easy to figure out from the drawing.

Click on "Building Height Defined" on the meft margin as the link does not take you directly to it.

PM me with any questions.

4. If the averages were used, a person could have a Garage that is 8 ft in height and a house that is 40 feet in height, and only have an averaged height of 24 ft. I think that it is time to amend the code.