I'm not sure what it would take to make a house blow that that. My guess is there was a home-made bomb in the basement. The cannon was most likely for looks...
I know personally that...
A) IF there was that much black powder in that basement I wouldn't want to be holding the match to light the cannon fuse...
B) Oxy-Acetalyne mixture tied off in a 55 gal. trash bag and shot w/ a roman candle makes a boom accompanied by a concussion that will knock the pictures off the wall of a house... or so i've heard