A contractor for "Tiny House Nation" has a big problem -- the couple who hired him is talking so much smack, they're crushing his bottom line ... according to the lawsuit he just filed.
Charles Brzezinski built a compact pad for Jared Logan and Vanessa Wesley on season 3 of the FYI reality show, but says they've since accused him of being a fraud and doing a shoddy job.
According to the docs ... Brzezinski says the couple posted a lengthy negative review on a consumers website accusing him of being an unlicensed contractor and crappy builder.
The contractor also says the couple posted pics that show the home falling apart -- but he says the images are of lousy work Jared and Vanessa did by themselves ... after construction was complete.
He also points out Jared and Vanessa happily signed a certificate of completion when the house was done ... and even has this video showing the place was immaculate when they got the keys.