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Anyone ever had to reinfoce their floor?

Living in a condo. Just finished plumbing my sump on a 75 gallon and leak tested my tank. No leaks, but unfortunately i noticed that as i walked by the tank it shook. I put a level on the tank and jumped up and down a few times and the level was all over the place. I live on the bottom floor and underneath is a 4 foot tall "crawlspace." Im guessing that i'm going to have to put some braces or something down there. Has anyone done this before? Ideas? Thoughts?
 

redfishbluefish

Officer Emeritus
Officer Emeritus
Phoobar Science

A conventional 75 gallon tank has a footprint of 18 x 48 inches. If we say a gallon of water weighs 8.4 pounds, then a 75 gallon tank weighs (75x8.4), 630 pounds. This calculates out to 105 pounds per square foot.

If we assume an average person standing occupies a 10x11 inch patch of ground, then divide your weight by 0.76 square feet. I’d suggest you stop jumping while using a level…that’s showing that something other than the tank is too heavy!

FYI, 75 gallons is no problem as far as load on modern construction.


DISCLAIMER: Load force is not as simply as determining weight per square foot. It is a very complex formula that needs to be determined by a structural engineer.
 

redfishbluefish

Officer Emeritus
Officer Emeritus
Well having never met you, I can’t say if you are good ;D. Again, I’ll repeat, it’s not the tank making the floor flex, it some other large mass. Your refrigerator is probably more pounds per square than the tank…put your level on that and walk by it. Or for that fact, put the level on any light object and walk past that.

You’re just fine with a 75 gallon.
 
redfishbluefish said:
Well having never met you, I can’t say if you are good ;D. Again, I’ll repeat, it’s not the tank making the floor flex, it some other large mass. Your refrigerator is probably more pounds per square than the tank…put your level on that and walk by it. Or for that fact, put the level on any light object and walk past that.

You’re just fine with a 75 gallon.


Are you trying to imply something???? It seems to me that you are saying that maybe, just maybe, he should feed the fish from the next room? ;D
 
Too funny...but I agree with Paul, I have a 125 with a 55 sump and didnt do a thing to my flooring.Not that Im saying yr senerio is the same,but for weight you should be fine. We all have heavier items in our homes ie- refrig,waterbeds,several people standing in the same area..best thing would be to check out the crawlspace to see whats up.Pics would help
 
LOL it is funny.

I had a 125 and had to reinforce my floor to be on the safe side. But I also live in a mobile home built in the early 70's and it is not on a slab foundation.

My solution was a platform of 2x10's supported by 6 30k lb floor jacks (not called lolly jacks but something else and I cant remember the name) mounted on a cinder block base.

A bit overkill but if a nasty storm comes through we know which part of the place would be left standing.
 

redfishbluefish

Officer Emeritus
Officer Emeritus
With this thread still active, I decided to try jumping in front of my 75 gallon tank. It is situated in the living room and happens to be positioned so that it is parallel to the beams below (worst case scenario). I weigh 220 pounds…all muscle in my dreams. I was shocked to see the amount of water movement in my tank. But again, it’s the mass of the a$$ and not the tank that is now causing the floor to flex that much. The solution is to either loose weight or to stop jumping next to your tank.

I will repeat, a 75 gallon tank is no problem on the load force of modern construction homes (past 70 or so years).

I will also tell you that when we put up the 90 gallon tank with a 40 gallon sump (130 gallons total), that was running parallel to the beams below, I did sister the two beams directly below the tank. I don’t know if it was necessary, but did it just to be on the safe side. You can see it in the tale of the tank here:

http://www.njreefers.org/joomla/index.php?option=com_smf&Itemid=26&topic=15806.15
 
justchad said:
a lot of us had to do it. home depot sells lolly colums in all lengths. I used 2 and a 4x6.

Same for me.


Note that I did it before I had the NJRC meeting at my house...I was worried that the extra 60 people in the house might be a problem...not exactly a small bunch of people either.
 
Thanks to everyone for their insight and input. It's just that it's the girlfriends condo and if something happened to the floor (like it breaks), i don't think i'd be able to fix it by the time she got home from work and there would be hell to pay...Hell Hath No Fury...
 
Sounds like the floor joists are under sized which makes a bouncy floor. My kitchen floor is like that, my 27 pound jack russel make it vibrate a little. Either you sister the joists or support them in the middle like someone noted.
 
redfishbluefish said:
I will repeat, a 75 gallon tank is no problem on the load force of modern construction homes (past 70 or so years).

This is not always true for a couple of reasons. The strength of your floor is dependent on 3 things:
1. The size of the joists
2. The span of the joist from one bearing point to the other.
3. The floor load, which is divided into 2 sub catafgories
a. Dead Load (permenant or semi permanant objects like walls or fish tanks.
b. Live load (a variable weight that comes and goes i.e. the typical "fat guy" scenario)

A typical floor structure can support significantly more live load than dead load because it only puts force on the floor for short periods of time (hours or days). A fish tank is a dead load and applies it's weight to the floor structure continually for the course of it's life.
Let's use the "fat guy" scenario that seems so popular on internet forums.
Lets say a fat guy comes along and sits on your chest. Painful yes discon=mforting absolutely but you can stiffen up and hold him for a few seconds or a minute. When he gets up you're able to relax and recover. The only lasting damage is to your dignity. But say that fat guy sits on your chest for a week or maybe a month. You won't be able to stay stiffened up for the whole time and eventually your chest will sink a little then a little more until your flattened.

Floor joist act similarly, they usually don't fail in sudden catastrophic events but slowly sag over time. Your tank should not shake as you walk past it and your floor shouldn't flex when you walk over to look at it. For a 4' high crawl space just put some extra support beneath the existing floor joists and support them with 4x4 columns. Peace of mind is a good thing to have.
 
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