The law here doesn't require every house be up to code every time the code changes. 90% of houses in NYC are not up to code actually. The law just says if you are doing an alteration, change the CO of the building, or doing a major renovation, then you have to bring those areas of the renovation up to code.
All I did was remove the old tile off the walls and tile over the old sheetrock to clean it up a bit. On the floor I went right over the old tile. Not necessary for me to bring things up to code.
Besides, I already have had tons of violations on that building that I worked out little by little with some left. Believe me, that 4" deficiency on one side of the toilet is the least of my worries.