Baltimore City Zoning Small Multi-Family

[Eric Masi]

I just went down the the Office of the Zoning Administrator in Baltimore City today and I was told that units can't be added to a building in zoning codes R1 - R6 (e.g. you can't turn a 3 unit into a 4 unit). 

I know that R1 and R3 are SFR only so it makes sense that they don't allow for small multi-family (e.g. a 1 unit turned into a 2 unit). But R2, 4, 5, 6 already allow for small multi-family to be built so it seems a little ridiculous that you can't, for example, convert a basement into a separate unit if you follow all the other building regulations.

Does anyone have experience adding a unit to a small mutli-family? Or experience getting something rezoned or some kind of exclusion or exception to the zoning? What about turning a particularly large garage into a unit like some people do with their "carriage house"?

I'm trying to figure out if it is at all possible to add value in this way. Any help would be appreciated, thanks!