Evanston's complex downtown zoning rules may get a fresh look in coming months -- though it's not clear whether whether aldermen have the appetite to actually open up that can of worms.
The City Council's inclusionary housing ordinance subcommittee has received a staff report suggesting a variety of changes to the code that would reward developers for providing on-site subsidized units by letting them build larger projects.
And aldermen from the city's three lakefront wards -- who often have the most reservations about high-density development -- have asked staff to explore a range of possible revisions -- from some minor tweaks to a wholesale rewrite.
The inclusionary housing ordinance subcommittee is expected to refine its proposals at a meeting after Labor Day. Both sets of issues are scheduled to be addressed at a special City Council meeting on Oct. 29.
The zoning code constrains development by setting limits for height, floor area ratio, setbacks, lot area per unit and parking. But it then offers a variety of incentives by relaxing those limits for developers who meet certain conditions.
The limits interact to create different restrictions for different parcels of land, depending on their size and dimensions and the zone they're located in.
Here's a rundown of the rules for the D3 zone, which offers the highest density in the city.
The base height limit is 85 feet. But up to 40 feet of height from floors that are primarily used for parking are excluded from the height calculation.
The current Inclusionary Housing Ordinance offers a 10 percent height bonus for including any subsidized units on a site near transit. That raises the base height limit to 94 feet.
The city offers extra development allowances to projects that go through the city's planned development process in which developers agree to provide public benefits as part of their project.
Essentially all sizable developments in the downtown area end up being reviewed as planned developments
In the D3 zone any planned development can get an additional 85 feet of height and ones that meet certain lot size and setback rules can get 220 additional feet instead.
Add it all up, and the hypothetical maximum height for a planned development in the D3 zone is 354 feet.
Floor area ratio
This is the relationship between the total square footage of the building and the square footage of the lot. A two-story building that covered the entire surface of its lot would have a floor area ratio of 2.0.
In the D3 district the base floor area ratio limit is 4.5.
The current Inclusionary Housing Ordinance offers a 10 percent floor area ratio bonus for including any subsidized units on a site near transit. That raises the FAR to 4.95.
A planned development can get an FAR increase of 3.5.
Proposed amendments to the Inclusionary Housing Ordinance would give a developer who placed all required subsidized units on site an additional FAR increase of 4.0.
Add it all up and the hypothetical maximum floor area ratio for a planned development in the D3 zone is 12.45 if the proposed IHO zoning change is adopted.
Lot area per unit
The zoning code also impose a further limit on density that sets a minimum square footage of the building lot required for each dwelling unit in the buiding.
In the D3 zone the base limit is 300 square feet.
The current Inclusionary Housing Ordinance gives a 20 percent bonus to that number for developments near transit.
The proposed amendments to the Inclusionary Housing Ordinance would give a developer who placed all required subsidized units on site an additional bonus of twice the number of subsidized units.
To illustrate how this works, imagine a planned development on a lot of 37,000 square feet -- about average for recent PDs downtown.
The base 300 foot limit would allow 123 units. The existing IHO bonus would increase that to 148 and require 15 subsidized units. The proposed IHO amendments would let the developer build 30 more unsubsidized units for a total unit count of 178.
It's worth noting that the lot-area-per-unit rule tends, in effect, to be much more restrictive than the height and floor area ratio limits and would require developers to build extremely large, and likely hard to market, units to stay within it and still maximize height and floor area ratio.
That's frequently led the the City Council approving projects that included more units than the lot area rule dictates.
Under most conditions encountered in the D3 district, setting the building base back from the front, side or rear lot lines is not required, although there are exceptions.
On some, but not all, downtown streets a ziggurat setback is required -- requiring that the building be built to the front yard lot line at the base, but that a 40 foot setback start no more than 42 feet above the base.
Under the Inclusionary Housing Ordinance, in areas near transit a development must provide half a parking space for each studio and one bedroom apartment, one parking space for each two-bedroom apartment and 1.25 parking spaces for each three bedroom apartment.
About the model
Now, returning at long last to the model at the top of the page.
Applying the existing rules to a 37,000 square foot hypothetical lot with dimensions of 200x185 feet, we concluded that -- assuming an average unit size of around 1,000 square feet and a unit mix of roughly 20 percent studios, 40 percent one bedrooms, 30 percent two bedrooms and 10 percent three bedrooms -- the development would hit the existing floor area ratio cap of 8.45 at a height of roughly 245 feet with a total of about 228 units.
With the proposed amendments to the Inclusionary Housing Ordinance in place, a building with a similar footprint could rise to the zoning code maximum height of 354 feet while staying within the increased floor area ratio of 12.45 and have a total of about 348 units.
Details of the calculations here.