2X6 to suport a live floor? sounds under code to me and I wouldn't put anything up there. you can sister 2X12's to them or install a metal beem to suport the tank, or use jack posts but that eats up carage space.

Steve

Cannot install telepost because it would be in the way of where I open the car door.

What about two teleposts on the sides of the garage so you can still park inside, and a metal I-beam spanning the distance? (Apologies if this was already suggested, I only just saw the last 2-3 posts here..)

Sistering with 2x12s adds strength without eating any groundspace.

A quick question for the experts and a little bit of a thread hijack..

What is the largest tank suggested for this same situation, if the tank is perpendicular to the joists and on an outside wall..without having to do any "renovations"?

210g on second floor
 

I put my 210 gal + other tanks on the second floor on my house. Assuming that you have 2X6 vertical walls, and that the support beam runs perpendicular to to outside wall, and down the middle on the tank -- I wouldn't worry too much. The amount of weight that a 2x6 can take is not a problem, (thousands of pounds per 2x6 depending on length and grade).

The real problem is the span on the joist. I had a span of 8' between support beams in the basement, which is just too much span with 2x8 joists. So I built a closet under the tank in the room.

There is little worry about "falling" through the floor, the problem is the amount of defection in the floor, or permanent "sagging". If there is a laminated support beam -- and you only come out 24" or so from the wall, you have a LARGE saftey factor with the main supports. Realistically you have 3' hanging out onto the joists, rather than in the middle of the room.

So, if you have 2500lbs, 1250 is on each side. if you hit 3 joists going into the room, you have about 420 lbs on each joists. But because you are only 3' out -- of you have a 12' span on the joists, you are comparable to about 1200lbs on a joist in the center of the span.

I have some calculations for the defection that I'll look up if need be. I planned for approx 1/16" deflection (which is over built) on my floor, and then built the stand using 2X10 beams on the upstairs.

I would be an engineer to properly look at it (and sign off on it for insurance purposes). But, at least -- build a good stand that loads most of the weight onto the beam and outside wall, and if you are really paranoid, sister up the joists (went from 3 joists to 11 because I could) under the tank. And remember that a good grade 2x4 48" will take almost 6000lbs by itself if not allowed to bend. Yes, 1 2x4 can hold a good size pickup in the air....

It's just the span and sag that you need to worry about.


deflection is (5wl^4)/384EI

w = weight per inch
l = span length
E = modulus of elasticity = 1x10^6

I = bh^3/12 (beam/joist width*height cubed/12)


so 2x8 joists

(1.5)(7.5)^3/12 = 52.7

5(3.12)(144)^4/(384*10^6*52.7) = .33 inch roughly

So a quarter inch of defection and that is with assuming the weight is further out into the center of the joist.

you should end up with about 1/8" in reality if you calculate the weight out over the span properly. And that is assuming that you don't have most for the weight directly on the outside wall.....

ok aparently I am all screwed up. If the Garage is unfinnished can you see the joists. the studs arn't to much of a factor as they can hold a house up which is way more than your tank.

Steve

wasn't in the OP the 2x6 studs, not joists.