I live in a carriage house that was built in 1926. It has a flat roof and I'd love to add a conservatory and deck similar to this. It would require adding another set of internal stairs to go up to the roof and possibly moving a gas heater (because I think that might be the best/only location that would work - see picture). I'm not sure if it's possible or how much it would cost, so I'm currently looking for an architect in San Francisco and would love to hear suggestions or opinions on my plan or on your experiences with any architects.