Rules on legal Apartments or Rooming houses in Canada?

K I've gone to the rentalsmen 3 times, useless, took a 2nd tennant (same landlord different house) house are falling in on themselves, plumbing nightmares, mold etc, who do you contact to report this to, also the rooming house is registered as an apt to fool the city, how do I approach that one. I'd let it go since I'm moved to a new place but the other tennant was a friend of mine that just got picked on cuz we were the last tennants to put up with this garbage in the apt building (empty building now, sending the worlds largest pimp in the to show off the place and hes to famous so no ones renting) I know the basement apt i was renting is totally illegal (doesnt meet height req. illegal building supplies, mold, sewer is failing, illegal wiring, illegal roof and worse) Just enough is enough ya know, if i dont stop the circle of this someones gonna end up dead at these places if nothings done.