Rationale for Zoning

Dear Management Doctor:

I have been going back and forth with our building official about various zoning ordinances. For example, (we argue about this one all the time) he does not understand why we regulate the height and size of accessory structures. He wonders why we do not allow them to be any bigger than 1,200 square feet and no taller than the primary structure. Any suppport to put this argument to bed would be helpful.

The Back and Forth Planner

Dear Back and Forth,

The building code primarily addresses health and safety issues, often related to structural issues. The zoning ordinances generally relate more to design and aesthetic issues including topics of light and air, traffic, and circulation.

However, you need to be able to answer the specific question the building official is asking. Many planners simply do not know the rational for some of the zoning regulations they are enforcing. They are similar to the regulations being used in other parts of the country or in other ordinances. If you can’t come up with a good answer, then I suggest you remove these provisions from your ordinance. I could give you my own speculation as to why your code reads the way it does but you should see if you can come up with your own reason.

The Management Doctor

Reader Responses

I thought it was 120 square feet. That's 20% of the typical rear-yard width. It has to do with lot coverage, minimum lot width, building code maximum for separate utility building in the rear yard, and has been in code books and zoning ordinances for ages. Go look at some and measure them to get a better feeling for what that really looks like, especially when the lots rear onto a public street! Two-foot increments have to do with spacing of studs. Anyway, those are some of my off-hand thoughts. It's a good question to throw at your planning commission. Regardless of minimum or maximum size allowed, it should be coordinated with the building code.

King Leonard

I agree that if the zoning regulation is not supported by a strong purpose statement in the document, a state law requirement, a provision of the comprehensive plan, or some other documented source, it probably should not be in the ordinance. There are good reasons for accessory building height and size limitations under certain circumstances, but these issues should be determined at the local level.

Rodney C. Nanney, AICP
Ypsilanti, MI

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