floor reinforcement?


New member
really at what point should someone consider reinforcing the floor of their house when putting in a tank? im planning to put in about a total of 130gallons(display/sump) all the rock/tank/sand/tanks etc probably be pushing 1500-1800lbs or so...

fairly new house, built in 94 raised floor blah blah blah who else has reinforced their floor for a large tank?


New member
It really depends on how the house is built,where the tank is, and whats the foot print of the tank.

I'd say a good rule of thumb is 100 gallons or 1000 lbs. which ever is 1st.


New member
I'm with TAB. You hit 1000lbs and you bess be considering the floor.

Yes most all floors will hold up a half ton but not without eventually deforming in some way.

If you are on a slab, fine.

On a foundation first floor, consider crawling under with some piers, chunks of 4x4, and sheetmetal tie plates to head off the eventual deformation.

Second floor? Gets tougher.


Premium Member
Most US city building codes require the floor to carry a "live load" of 40 pounds per square foot. If your tank covers 8 square feet (2" x 4") that is 320 lbs (~45 gal) even if it is in the center of the room. Like MeuserReef said, if you place the aquarium close to a bearing wall with the aquarium on as many floor joists as possible the load can go up significantly (I think easily 1000 lbs).


New member
hummmm thats good information.....im about 95% sure the wall is load bearing its going up against considering its a common wall through both floors of the house and right in the center lol.....i think im going to reinforce it my uncle said he would help me do it (he's a contractor built my moms house to)

that leads me to think honestly who else has reinforced the floor of their crib?


New member
Think about something here folks. All the load from your second floor is transfered thru walls to the same support structure as the first floor (so is the roof for that matter). Now its is possible that your first floor has joists of 10" height and the second my have 8" joist height, so if the wood (pine 2"x8"X8") has the ability to hold the weight (or if spanned across multiple joists) you should not have any problems. Also, I learned a long time ago that the strongest part of a floor is the center, not the edges. You may keep your floor from bending if you keep things close to a wall, but you also introduce shearing between the wall and the joist that only sits about 6" on top of that wall. Now you have traded a possible general bend in your floor(tank in the center of the room), for the possiblity that you could shear a joist and have the entire tank go thru the floor (not likely I think either, but thats the trade).

My fat A$$ is about 300lbs, my oak desk was at least 500lbs (yeah its big) , add my computer, everything in the drawers, my chair, hundred of pounds of books, not to mention the 110 gallon aquarium I have on the same wall in a loft over the living room, and I have zero distortion in my living room ceiling.

Does you floor have a TV, a shelf to put it on, couch, chair, end table ........ piano!!!!, add up the weight with you A$$ on the couch and you my find yourself not worring too much about 1000lbs.

For those of you who have the occassional weekend party, then you know what it is to have maybe 20 people in one or two rooms, I can almost guarantee you have exceeded 2000lbs.

Sry about the rant, but I've seen this question asked soo often that we could use and engineer to give us some explainations that we can make a sticky out of.


New member
One more thing, if you ever owned a water bed, you may find that a rough calculation will give you about 1700lbs of water spread over about 36sqft. Thats well over 40lbs/sqft.


New member
There is little doubt that any floor will hold almost anything we'd put there. That is not the question. It's about the deformation...

Aquariums are long term devices. They aren't a party. They don't move around. They aren't a dynamic load. I put a safe in one bed room. It has a completely smooth bottom 3ft x 4 feet. It's not light. I'd say it's about 1200lbs as it's lined with Sheetrock. It sat there for 4 years. It left a rectangular depression in the hardwood oak flooring!

I moved it to another room. After three years that room has a crack running across one wall and the door which is parallel to the tank and 4 feet away is now visibly askew in the door frame and doesn't open easily.

You can talk all day about how the structure will hold up heavy dead weight and I will agree that it will. But we are talking about large heavy loads that will effect the structure eventually - subtly. If you were going to put a 1/2ton or more load somewhere in a house the architect would certainly take note and probably do something extra for it.

Take your uncle's offer up and reinforce your floor. Feed him a nice burger afterwords. You won't regret it.

My 165gallon 12 foot tank was put directly against the central support wall I added a horizontal pressure treated 4x4 under the front edge. It's supported by three vertical supports on pier blocks. I have never seen any deformation I could logically attribute to it in 14 years of celebrated dead-weight.


New member
<a href=showthread.php?s=&postid=14799501#post14799501 target=_blank>Originally posted</a> by ConsultantERP
One more thing, if you ever owned a water bed, you may find that a rough calculation will give you about 1700lbs of water spread over about 36sqft. Thats well over 40lbs/sqft.

The 40 lbs/ft2 thing is what structure wieghts, not what it can hold.


Welcome to the next level
40 lbs/ft² is the "live load" rating. The actual weight of the structure itself is considered "dead load"

From the article linked above:
Let's begin with a few definitions:

Dead Load: This is the weight of everything that is permanent such as the floor joists, walls, piping, ductwork, floor tile, etc.

Live Load: This is the weight of everything that you add to the house or apartment when you move in. Furniture, bookshelves, people, appliances, and of course, your computer and your aquarium(s).


New member
consultant: i think the point here is not if the floor could support X pounds but but in reality can it support that same weight in a smaller area IE like a fish tank thats 60 long * 18 wide....think about it this way, take a 15lbs piece of iron and you smash that into a 6"x6"x6" cube put that on a sheet thats attached to 4 poles at each corner put that weight directly in center its going to BOW down ALOT!...take that same piece of iron, smash it down to 12"x23"x .25" it spreads the load out immensely which would result in far less bowing...

the argument about a house party that 2000lbs or so is spread out evenly much like the flat piece of iron in example above. as well as the water bed falls in this same example your spreading that water over a much broader area (in the case of a queen size water bed your spreading it over about 4x the same area IE most likely 4x the amount of braces.

im just thinking this is a enormous amount weight to be in one central location, that doesnt move and will not EVER move

after seeing the safe thing i think i will look at reinforcing the floor soon.

maybe we should make something like this a sticky because i have never seen this topic come up...

in case of search feature many things to think about here in determining the weight of the tank setup

on average
100gallon glass aquarium weights 182pounds
sand 100pounds
rock 100-150pounds
salt water is 1gallon = 8.5pounds (850pounds)
light fixture 10-20 pounds
stand 70 pounds roughly

say 50gallon sump 100pounds for the tank
you only put say 30-40gallons of water so 255-340
rock optional
RDSB 20 pounds
autotop off 10gallons (freshwater is 8pounds/gal) so 80 pounds
misc odds and ends (pumps, skimmer, powerheads) 20lbs ( my mag is heavy)

roughly a 100gallon setup would be 1837 pounds in a 60x18 area which if im right each brace supposed be 18" apart from each other i think is code so, it would span over 2-4 braces


New member
The joists will be no more then 16" apart on center, depending on what was used, they could also be 12" on center, but thats rare.


New member
I went THRU my floor down to the dirt with some wide concrete pads that the legs land on. Wife was REEEEAL happy too


New member
It's possible if you position the tank parallel to the floor joists that it could straddle a single joist. In that case a large tank is doomed to destroy the floor. However, if the tank will be perpendicular to the joists then you could get it over 3 or 4 joists so the chance of success without additional bracing is much better.

The other variables to consider are wood type and unsupported span. If you put your sample tank over 4 floor joists with only a 5ft span then I think it would be fine. If that span were 10ft or so then the story changes. Also, take into consideration the size of the joists. Generally this is determined by the span but in a situation where the spans are of a variety of lengths (such as in my house) the joists are designed to support the largest span but I also have some areas with minimal spans, such as the 5ft I mentioned earlier.

Bottom line - if you don't feel comfortable then take the effort and time to support it further. You'll sleep a whole lot better at night whether you really need it or not.


New member
GET a PROFESSIONAL!!!! to come look at at i paid 90$-for a structural engineer to come out look at the joists and other variable b4 i went ahead with my build. also if it doesnt fail right away dont think that means it wont. peace of mind is worth allot in this hobby.


Elite Member
Another thing to think about is the tank itself. Without bracing under the floor, it will wiggle, bounce, wobble, twist, shake and so on as people walk by. The more the floor gives the more undo stress is put on the tank and could eventually lead to issues with the seams of your tank or even stress fractures in the glass or acrylic.

Here's a good example of what a floor that gives can do to a tank.

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