I've been a Chicago Realtor for over 15 years and a coach house owner for the past 20 years. Several years ago, I renovated my coach house, however I did not add any square footage. In the current Chicago building code, you cannot expand a coach house. The reason is coach houses may not be built any longer in Chicago. Existing coach houses are grandfathered in the law.
If you have a building in the front of the property, and a second residential building in the back of the property, then the second building is a coach house.
Consider raising the home with re-claimed Chicago brick. But do the exterior work quickly. Very quickly. If anybody complains simply state that your home was always that height. Make them prove otherwise!
Or find out where the zoning department head eats lunch. Be there first and pay for him. Do that for a week. Might help.
17-15-0303-C Detached houses that are a nonconforming use in a B, C or M district may be expanded by up to 30% of the structure's existing floor area, provided that such expansion may not exceed the maximum allowable floor area ratio of the district in which the structure is located.
17-15-0303-D Nonconforming coach houses on properties designated as official Chicago Landmarks or located within the boundaries of a Chicago Landmark District may be used as a dwelling unit for a single household if the Zoning Administrator determines that competent evidence exists that the coach house was previously used as a legal dwelling unit. Incidental repairs and normal maintenance necessary to keep nonconforming coach house in sound condition are permitted, but no expansions are allowed.
17-15-0303-E Nonconforming coach houses on properties outside the boundaries of a Chicago Landmark District may continue to be occupied as dwelling units provided that they have not been continuously vacant for more than one year. Incidental repairs and normal maintenance necessary to keep nonconforming coach house in sound condition are permitted, but no expansions are allowed.
17-15-0304 Loss of Nonconforming Use Status.
1. If a nonconforming use is discontinued for 18 continuous months or more, all nonconforming use rights are lost and re-establishment of the nonconforming use is prohibited.
From experience, I would tell you that your time, effort and money is probably better spent on other housing options given our current real estate market. If you are dead-set on the renovation project I have one more idea that might help your "this is not a coach house" argument.
I spoke to the Alderman's office this morning and they said that I should have an architect do drawings (expensive if I'm not sure I can build) then come back to the Alderman's office and then go back to zoning. Seems like a big roundabout.
However, being familiar with the building code (I practically have it memorized at this point) I called zoning back today and asked someone to tell me the City's definition of a coach house. Apparently there isn't a written definition. That gives me hope. The gentleman I spoke to said I can write up my situation and for a mere $50 I can request an advisory opinion letter from the zoning supervisor before hiring an architect. Does anyone have experience with this?
When I went to zoning the first time, we confirmed that we still have nearly 1000 sq ft to play with based on FAR and we acknowledged that based on our hand drawings that we would need a variance on the rear setback. I'm hoping that since there seems to be at least a little ambiguity on the definition of a coach house and that we still have sq footage left to play with that, if I write my argument well enough that we might be able to pull this off.
I am renovating a coach house right now and dealing with the city is challenging to say the least. A coach house is an existing non-conforming use, so you can usually permit limited work to the structure; however, the city will not let you expand from the existing footprint of a coach house (I recently tried this and got denied by zoning). You may also run into problems depending upon the zoning and set back requirements of your lot. If the existing liveable space above grade exceeds your allowable FAR (floor area ratio) calculation the zoning department may find yet another reason to not permit your project. Rather than reaching out to the alderman, I would consult an architect at this point of the project.
I can answer more of your questions once I have a better idea of your situation. Call/email me if you would like to talk.
RpV Realty and Development