The Plan Commission on Wednesday night, September 12, voted its approval of changes in the zoning ordinance regulating what homeowners can build above the second floor of houses in most R zoning districts. Ostensibly designed to limit a tendency toward de facto third stories, the proposed changes, detailed at pp. 30-36 of the Sept. 12 Plan Commission packet, will, overall, permit more construction at upper heights in residential districts.
Under current zoning, houses theoretically can't be more than 2-1/2 stories, and new construction and additions are limited to 35' tall. That maximum height is measured using the mean between the roof's high and low point, so a roof can actually peak at 40' or higher. The "half story" is so-called because "liveable" square footage (space with a 7-1/2' or taller ceiling) above a second story is limited to 60% of that of the second story. So a house with 1000 s.f. on the second floor can have 600 s.f. of attic "liveable space" above that.
As a practical matter, only half of the space under a typical peaked gable or hip roof is "liveable" height, so owners and developers of peaked-roof houses to achieve 60% or more use dormers, currently limited to half the length of a roof, to push out portions of sloped roofs.
The overall result has been, as City staff put it, new construction or additions that "dwarf" neighboring houses because of actual height and bulk; top stories often don't resemble an attic but feel, to a neighbor, like a full third story next door.
The new ordinance, which has gone through several iterations over the summer, changes maximum height measure to absolute peak, not mean height, of a roof, and would reduce the percentage of dormers allowed along a roof's length. These two changes will modestly curtail some top-story bulk strategies. However, they are more than offset by the new ordinance's three dramatic amendments: (1) elimination of the 60% cap on a half-story space, (2) the allowance of a three-foot-high "knee wall" for gable and hip roofs, and (3) the elimination of limitations on building on substandard lots.
The "knee-wall" permission would allow a roof to start three feet above the top of the second story, meaning that inside the attic, the far corner of the room could be three feet tall rather than zero. This change alone will allow hip- and gable-roof attic spaces to achieve at least 70% "liveable space," nearly 80% if dormers are added to the maximum allowed. Meanwhile, mansard and gambrel roofs, no longer constrained by the 50% cap, can ascend at steeper angles. Thus, for all houses, unless the first two floors already are more than 22' or so above grade, significantly more construction will be allowed of houses that are essentially three stories, although that top story will be primarily covered by roof.
These changes apply only to new construction or to houses built within the last 50 years. Older houses, and those in historic districts, will be governed by the old limitations, at least as to height.
An additional significant change likely to affect the teardown market is the proposed elimination of limits on "substandard lots." Currently, each residential district has minimum lot size standards so that houses do not overfill lots, creating a sense of crowding and depriving neighbors of light and air. For example, in R1 districts, lots are supposed to be 7200 s.f. Lots smaller than that district standard have their permissible height limited by 15% to 25%, depending how small the lot is, so that the bulk of a house stays in proportion to the lot. Under the new ordinance, however, this limitation will be eliminated, letting most owners build as high as any other regardless of lot size.
The principal exception to the new relaxed limits may be for newer flat-roofed houses. Or not. Because the half-story and knee-wall definitions are inconsistent and confusing, it at first seems, as staff explained, that flat-roof houses can't have that, even if their half-story volume is no greater than sloped-roof houses' attics. However, until the language is fixed, a legal argument could be made to the contrary.
Because most "substandard" lots are in subdivided portions of Evanston where the majority of homes are smaller, relaxing this limit, assuming past patterns and normal market forces operate, will result in more development on blocks with smaller cottages and bungalows.
A less-debated change to the ordnance will eliminate mean height as the measurement for accessory buildings (usually garages), raise permissible height to 20' for most, and lower it to 14' for flat and mansard-roof structures.
Plan Commission approval of the ordinance is not the final step. Any text amendment to the zoning ordinance must be passed by the City Council after notice and hearing.