Office addition to 100 year old house

[Jim Fischer]

Hello,

I am having trouble locating some information on having a modular addition to a two-story 100 year old mid-western house. This house is being used as a convent for a group of nuns. They need to add space for offices. This new space would be a slanted roof from the existing structure - i.e. it would be built along side the existing structure. Nothing would be needed inside except utilities, and walls - perhaps an extra lavatory. Ability to match the exterior siding is important, too (white siding). Certainly cost is an issue. Location is Rockford, Illinois. Any help would be greatly appreciated.

Jim