Yes, I too ran into this exact same situation, building out a delco. We had an existing restroom in the back of the store when I leased my space. I planned to blow out the walls and make it ADA compliant, but when I went to review the plans with the city I was told I had to have a ADA compliant, publicly accessible restroom. The inspector actually wadded the plans up and threw them at me, but that is a different story for a different day…
I had to dig up a brand new ceramic tile (the landlord had it there) job run sewer underground an extra 30-40 feet and of course fill it back in and re-tile. On the tile I never expected to match pattern exactly but figured I could come close and just re-tile the portion we dug up. Come to find out I could not even match the size of the 16 inch tile, they seem to have fallen out of vogue and are rarely made these days. Then I tried to match on a multiples of 16 such as three rows of 16 inch so 48" and replace with 4 rows of 12" or 2 24" or something like that and I am now up to 3-400 square feet of tile to replace and it still doesn’t match the original. One of the tile places came up with a really attractive tile for about $1 per sq foot so we just re-tiled the whole store (1000 square feet). Total additional cost is probably in same ballpark of 10,000 for adding this public restroom.
For the final kick in the pants, I am thinking hey as long as I have a public restroom I can add a few tables so ok, I will play along because I like that option. When we went through the inspection process, the city tells me that if I add a single table to my lobby (which probably has room for two or three, four person booths) I need to have separate mens and womens restrooms! I am not open yet, but once everything is finalized and some of the grand opening attention is away from us, we may test this rule or god forbid go through a variance process because I think this is a little over the top.
Historically speaking though I have been around delco’s for twenty years and only very recently do I see this being enforced.
I am in Metro Detroit for reference. Sorry you are facing this additional expense!