All Dwelling Units Are NOT Created Equal

Almost fifty years ago I wrote a publication entitled “All Land Is Not Created Equal”. This was the age of Ian McHarg and the beginnings of what we might call environmental land use planning. The publication was primarily designed to expose lay planners (but also professionals like surveyors) to the concept that everything on the face of the earth is not the same – there are wetlands, floodplains, steep slopes, areas unsuitable for septic systems, etc. – and should not be treated the same as we plan for the future of our communities and regulate land use and development.

Now almost a half century later, I ask if we need to think about dwellings or dwelling units in the same way and recognize that they are not all the same. A one-bedroom or studio apartment is different than a four bedroom single-family home. And they each have different impacts or externalities which are what we are supposed to be regulating. The Census tells us that the occupancy of different size units is on average different although this isn’t always true at the local level. In general, the more bedrooms in a unit, the more people in a unit. Smaller units typically use less water, generate less sewage, have fewer school children, generate fewer peak hour trips, etc. Look it up! Ask your school department how many kids per dwelling unit come from that apartment building versus that new single-family subdivision. In Maine, we require a septic system that serves a three bedroom single-family home to be larger than a system for a one bedroom apartment – why? You know the answer; more bedrooms equal more sewage to be treated.

Now think about how local land use regulations (or zoning) regulate the density or intensity of residential development. While the proponents of form-based code and similar approaches argue that density or lot size/area requirements should not be used, in fact they commonly are. Most zoning ordinances establish minimum lot sizes or minimum lot area requirements -- something like 20,000 square feet per dwelling unit or three dwelling units per net residential acre. They regulate density based on dwelling units. But if you read the preceding paragraph, you know that all dwelling units are NOT equal, that they have different impacts and when you think about it, you might start to question if regulating residential density based on dwelling units makes sense.

Let’s say your ordinance says that you have to have 20,000 square feet of lot area per dwelling unit. So you can build a four or five bedroom home on a 20,000 square foot lot. But if you want to build a small apartment building with say four one-bedroom apartments you need to have four times 20,000 square feet or almost two acres. Think about what that does to the creation of rental housing or affordable housing – it is a killer! So rather than deal with the real problem (using dwelling units to regulate density) we create all sorts of crazy work-arounds like density bonuses (based on dwelling units) or special districts, or contract zoning (let’s make a deal zoning) to allow what the ordinance should allow by right. These types of things deter even experienced developers.

So what is the alternative? I have been working with using bedrooms or bedroom density as the regulatory standard and have incorporated it into a number of ordinances in different ways. But I’d be the first to admit that it is a work in progress and is not perfect. Here are a couple of approaches. One is what we might call the fractional unit approach – a small, one-bedroom unit only counts as say 40% or half of a dwelling unit for lot size or density requirements. So you can double or more the number of one-bedroom units allowed on a lot. And it is an easy ordinance amendment since it can be a simple universal change. This also works for two-bedroom units. A handy approach for allowing duplexes with two bedroom units at a higher density without changing the underlying density standard for single-family homes. A second approach is to use bedrooms rather than dwellings in the density standard – a minimum lot size of say 7,500 square feet per bedroom. This has to be done carefully and may only be applicable in certain situations especially when dealing with single-family homes.

Thinking about bedroom density and how it can be used to allow smaller and more affordable units should be on the top of your to-do-list. Dwelling unit density provisions have contributed to the current housing crises. Bedroom density provisions can contribute to the solution if used wisely.