# Dwelling Units Defined by Unit Size

#### hcplanner

##### Member
I have a developer that has asked about changing the definition of a "dwelling unit" in our land use code. He would like to make the unit based off the size of an apartment. His argument is that one of the primary goals for zoning is to control density and there is a difference between density when you compare a studio apartment to a 2 or 3 bedroom apartment. He is suggesting that we define the units based off the number of bedrooms in that apartment. For example a Studio or 1 bedroom may be considered .33 unit, a 2 bedroom .66 units, a 3 bedroom 1 unit, etc. Right now our ordinances for a multifamily property just states how many units per acre are allowed but there is nothing in the definition for a "dwelling unit" that says how big a unit is. This would allow the developer to have more apartments if they were smaller apartments as opposed to larger apartments. Is there anyone out there that has seen it done this way? or are there any thoughts on advantages or disadvantages to doing it this way?

#### Faust_Motel

##### Cyburbian
Yes. We use a DU-equivalent. One bedroom or studio = 1/2 DU. Anything more = 1 DU.

#### DVD

##### Cyburbian
Nope. When your fair city created the density numbers they expected all of these mixes. It's worked for years with no problems. Why would you change it for this guy? Think about the math at 10 units/acre (using 1 acre of land):
Studio: 33 units
2 Bed: 16 units
3 Bed: 10 units
Make sure I did my math on the fly okay, but the answer is hell no.
The developer is just trying to maximize their rental income or create a mix that's more favorable to the current market. It all sounds like some slumlord thing in the end.

#### Faust_Motel

##### Cyburbian
I'll clarify that this change as made in our zoning by the electeds some years ago, not for any particular project. I'd never make a DU definition interpretation on the fly like that, if that's what your developer is suggesting.

In our experience, most of the apartments being build are still 2BR, but some of the larger buildings (55-65 units) might get a few studios sprinkled in there. Nothing too earth-shattering.

#### DVD

##### Cyburbian
I could see it working on a larger property like Faust said. Sprinkle in a couple and no big deal. Sadly my city would have too much of the wrong people trying to create nothing but 1 bedroom or studios just to cram them into small lots. Maybe there is a breaking point you can write into the code. After 50 units we'll allow a reduction in density for studios?

#### mendelman

##### Unfrozen Caveman Planner
Staff member
Moderator
This is an interesting way to look at density theory that I haven't experienced yet.

My long time understanding of why dwelling unit density exists is due to the external impacts of a new dwelling unit. So, a dwelling unit has definable capacity impacts on roads and water/sanitary sewer/storm sewer provision. And more indirect impact on schools and emergency services (fire/police/ambulance).

So, you're a planner for a community with greenfield residential development (or, if built out, redevelopment) capacity and need to figure out how to ease into servicing anticipated development.

You, ideally, run build-out capacity analyzes and determine a maximum DU density from there. Understanding the presumption, likely, that the base for a DU is at least one kitchen, one bath, one resident&car.

Starting to look at a DU base being one kitchen, one bath, two bedrooms probably has some sort of objectively greater impact to counts as 1 DU, but I'd really like to see the math on that.

I guess it's a matter of then getting into the subjective political decision making about where to draw 'The Line'.

It's analogous to deciding on a maximum sign area standard. It's effectively arbitrary, but, for enforcement purposes, you just need to set a number.

hcplanner - Run the political calculus on this from your employer's perspective and make sure to greatly manage the requestor's expectations regarding your potential support and certainly make the requestor do all the heavy lifting on this request for as long as necessary.

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#### Faust_Motel

##### Cyburbian
This is an interesting way to look at density theory that I haven't experienced yet.

My long time understanding of why dwelling unit density exists is due to the external impacts of a new dwelling unit. So, a dwelling unit has definable capacity impacts on roads and water/sanitary sewer/storm sewer provision. And more indirect impact on schools and emergency services (fire/police/ambulance).
Right- we have a separate sewer capacity purchasing program and "budget," which is informed by our density rules and vice-versa. That adds a comfort level to treating density the way we do. For sewer capacity, it's the first bedroom that generates most of the capacity demand.

Also, although we use an equivalent for density purposes, for impact fee purposes a DU is a DU. (there's a different dividing line in our impact fee rules, with attached units paying slightly less than detached.