Floor joists- how many?

  • We are currently upgrading MFK. thanks! -neo

Iwannabreedit

Feeder Fish
MFK Member
Jul 17, 2012
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Canada
Hey guys! I have a 72 x30x30 280gal tank and I was wondering how many joists should it sit on to call it safe my house is1 1/2 years old and the tank will be above the garage close to the wall and that wall is all cinder blocks. The floor joists are every 24" for some reason and they are the I beam joist not regular 2x8 or 2x10s, apparently these newer Ones are stronger but I'm not 100% sure. Someone please help :) oh and those I beam joist are roughly like 2x10ish
 
Hello; I have not used them yet myself but it is also my understanding that the engineered joists are supposed to be stronger than dimensional lumber. My guess is that being at 24 inchs on center will likely result in a floor loading capacity similar to the more traditional floor joists. Stronger but spread thinner? You may also have roof trusses at 24 inches on center as several newer houses I considered buying had this as well. Perhaps someone with current experience can add to this?
I will include in this post some information that I have posted in the past about floor capacities. I do not recall if any of these web sites deal with the newer trusses.
A 280 gallon tank might weigh around 2800 pounds to over 3300 pounds with stand and other equipment.

Hello; here is the web address of an article that talks about the issue.

http://badmanstropicalfish.com/articles/article28.html


Hello; Tanks can weigh from 10 to 12 pounds per gallon depending on the amount of gravel and equipment used. Water is around 8-1/2 pounds per gallon and to this the weight of the tank itself, the stand and all other things must be added.
(OLD RECYCLEDPOST some words will run together, this happens when I copy and paste to the forum)) Here are some web addresses about floor capacity. The first address is a new one from a post by another Monster Fish forum member a while back. Here are the addresses again with the first being new to the list. Floor capacity depends on a lot of criteria, there is not a simple answer to the question.
This web address is added to the list http://www.cichlid-forum.com/articles/aquarium_weight.php It is perhaps the easiest to follow.
http://www.ehow.com/how_7485788_calculate-floor-load-capacity.html
The web address above is a site about calculating load capacities of floor joists. They use a formula for the strength of a beam: maximum load in pounds = FBd^2 / 9L.
The width of the wood joist in inches is B (1.5 inches for standard 2 by dimensional lumber.)
The depth in inches is d (7.25 in for a standard 2x8.)(9.25 in for a 2x10)
The distance (span) in feet is L (Unsupported distance)
F is something called the fiber stress when wood bends. It varies with the type of wood but graded lumber will be at least a 1,000 number, some are higher.
They use an example of 2x10 floor joists with a span of 14 feet on 16 inch centers and come up with 1,019 pd for each joist. They figure the area supported by each joist as 18.7 sq ft. They get 54.5 pd per square foot of floor area. I think this includes the weight of the flooring and anything else that is supported by the joists.
I looked at some other sites (Addresses listed below) and found a discussion of static loads and live loads. Two sites describe how to measure the deflection of flooring due to weight loads.
http://www.johnbridge.com/vbulletin/deflecto.pl

http://www.awc.org/calculators/span...d=10&submit=Calculate+Maximum+Horizontal+Span
I found these sites interesting but hard to pin down for a general rule of thumb. Too many variables involved; Type of wood, condition of wood, dimensional lumber or engineered truss, age of wood and on and on.
http://www.eng-tips.com/viewthread.cfm?qid=62845&page=10
 
The plywood subfloor is probably tongue and groove, glued and screwed which will transfer load to the other joists the tank is not sitting on. If it is on an outside wall and the joists are run perpendicular you should be fine, given the I joists have not been compromised. Fill it slow and look for deflection and listen for movement. My 180 gallon is on 100 year old framing and has not moved.
 
GOod info guys. There are some areas where the joists are every 16" like under the washroom and areas like that but im pretty sure as well that I won't have a problem because from wall out my aquarium will be 35 inches(from wall to front of aquarium) . So the aquarium will be sitting on 3 joists and the majority of the weight will be resting on the cinder blocks. Iam sure those joists won't bend at 35" off the blocks... Well I think so
 
GOod info guys. There are some areas where the joists are every 16" like under the washroom and areas like that but im pretty sure as well that I won't have a problem because from wall out my aquarium will be 35 inches(from wall to front of aquarium) . So the aquarium will be sitting on 3 joists and the majority of the weight will be resting on the cinder blocks. Iam sure those joists won't bend at 35" off the blocks... Well I think so

Hello; Builders will make bathroom/washroom floors a bit stronger as they can carry a lot of weight with heavy stuff like toilets and full bathtubs.
Good luck.
 
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