Doesn't DC have large areas of single family residences? Could you work in a garage?
Around here there are a number of small shops that cross the line between storage facilities and small space workshops. I'm not quite sure what they are called.
I had a friend that had an art studio with electric welding in a second floor studio apartment in Brooklyn. But the last time I saw him was in the mid 1990's. I think there was a lot of wood in the loft, but a thin covering in the welding area.