Justin Bieber -- Dad Trashes Home ... And I'm Getting the Bill!

Justin Bieber has become a dad to his dad ... not only paying the elder Bieber's rent ... but he may have to bail his father out for TRASHING the home he was renting.

Jeremy Bieber leased a house in Kitchener, Ontario from October 2011 to September 2012. The landlord claims he left the place in shambles ... pet urine and feces stains all the over place, a toilet that busted after someone flushed a hairbrush down it and lots of other stuff.

A judge saw it the landlord's way, and according to legal docs -- obtained by TMZ -- ordered Jeremy to pay $12,852.93.

But Jeremy's sugar baby Justin will probably foot the bill, because it seems he's paid for everything else. The landlord attached a wire receipt showing Justin covered the $1,650 monthly rent.