<a href=showthread.php?s=&postid=7826030#post7826030 target=_blank>Originally posted</a> by kalare
Not everyone has a basement or crawlspace, many houses are built on concrete slab. Even if he does have a basement or crawlspace, this doesn't mean the floor joists run the same way, this is in fact a bad assumption as I have designed many houses, and many have opposing joists.
And to all the people saying it'll be fine setting the tank perpendicular to the joists, this is quite possibly true, but all situations differ. Depending on the size, spacing, grade of wood, and length of joist, there is a GOOD possibility of problems. If you own this house, you should have blueprints or plans for it. If not, all building records are public by law, so you should be able to find something.
How about you draw and layout of the floor, and where you want to put your tank with some measurements (wall to wall length, room dimensions) and then we may have a better idea of what will and won't work. Also, if you have any areas on the first floor with unfinished ceiling (closet, under a light fixture, etc) try to figure out how deep your joists are, then we'll be in business. Give some more info, maybe I can help.