I spoke with a local AIA architect in order to get a better grasp of last night's amendments to the McMansion and duplex ordinances.
Some good news and some bad news (or some bad news and some good news, depending on your perspective.)
The duplex ordinance amendment was not as dire as I had feared because of changes to the ordinance originally proposed by the Task Force. As I discussed here, the Task Force had recommended that the common wall between two duplexes be perpendicular to the front lot line. This essentially would have mandated that all duplexes sit side by side or on top of one another (the latter, an unpopular choice), thereby banning duplexes on long, narrow lots.
The ordinance language as enacted, however, omits the perpendicular-to-the-front requirement and permits the common wall to be articulated in 4-foot segments. A skilled architect can use this provision to fit a longer common wall (two times as long) within the same amount of space. This will allow duplexes to be placed front-to-back on a long, narrow lot. While the lot might not have enough space from one side to the other for a straight common wall, it might be wide enough for this articulated common wall.
The neighborhood types wanted to eliminate this "zipper" provision because, I assume, they don't want duplexes aligned from front to rear. City staff pushed for the zipper provision, which made it into the version adopted by Council.
The "bad" relates to basements. Basements that meet certain requirements do not count against the maximum floor-to-area ratio. One of the requirements is that the basement be below a certain "grade." The Task Force recommended (and Council approved) a requirement that the basement be below both "natural grade" and "finished grade." Others (including the AIA) wanted to stop at "natural grade."
Here's the issue, as explained to me: Requring a basement to be below natural grade provides sufficient protection. Natural grade is the land's undisturbed state; a developer can't build a "pedestal" by pushing dirt around to sneak in an above-ground third story.
But requiring that the basement also be below "finished grade" precludes a "walk-out" basement. Even if the basement is below natural grade, if you make a cut in the natural grade to create a separate entrance to the basement, you are now below the "finished" grade. This means that "walk-out" basements will not be eligible for the FAR exemption.
I don't think basements are very common today because of their expense, so I'm not sure how big a deal this is. However, they may become more common in the future as developers and homeowners turn to them for otherwise verboten floor space. This amendment will preclude their use as separate apartments.