I am a professional custom home builder, and finish carpenter. it is cantileevered to 2x lumber specs and has several (5)dobled up joists in the upper and lower sections running from back to front and is supported in the center section by corner posts and a header going between all corners which are carried by jack studs , in a nutshell it's built like a house it has been usd for 2 years no cracked tank and has to weigh 75-100 lbs.