A bulky couch. A narrow stairwell. A sprinkler head. Put them together and what do you get? Millions of dollars in property damage. And an insurance company that refuses to pay because the incident -- couch vs. sprinkler head -- happened inside a luxury downtown condominium, and not on the street.

This sorry, soggy tale is playing out at the Textile Building -- at 66 Leonard St. in Tribeca -- according to a current lawsuit.

The case hinges on the definition of ‘loading and unloading’ -- and whether the moving truck was being loaded while the errant couch was inside, still upstairs.

The stately, 14-story edifice -- an office building converted to condos in 2001 -- holds apartments that sell in the $3 million to $5 million range.

The headache began a year and a half ago, when someone on the sixth floor was selling a couch through Furnishare, also known as Kaiyo — an online marketplace for high-quality used furniture.