Re: More Floor Loading for large tanks

["S. Hieber" <shieber at yahoo_com>]

Diana hit some nails right on the head, point the way to
relatively simple methods for support your large tanks:


> I have been taking some drafting courses here in
> NY.  Some of the rule of thumb I was given was that
> the average home built to code uses a system of floor
> joists to allow for 35 pounds/square foot of floor
> loading in an average residence.  So if your joists
> are 2 by 6 on 16 inch centers you are probably in this
> ballpark.  

Well and good except that aquaria, life refrigerators, are
concentrated loads, so the 35 psf doesn't really presetn a
maximum aquarium weight.  What matters also?  Diana went on
to say:

> The unsupported span of the joist is a
> critical factor that needs to be assessed.  Commercial
> structures (like office buildings) generally allow for
> 150 to 200 lbs/square foot of loading to accomodate
> the loads of filing cabinets.  I believe floor joists
> in this case would average about 2 by 12 on 16inch or
> 12 inch centers.  


I belive the factor here is called "Stress in Bending." 
There are different values for different woods and
dimensions of joists.  Not that the longer the joist is,
the less stres in bending it can handle -- jsut ry to bend
a 6" long 2x10 joist ;-)  

> Unsupported spans then become the
> issue.  If you are doing this in your home, I would
> suggest putting some colums/beams under the immediate
> joists that will support the joists to bear the tank
> load, just to be on the safe side. Remember that along
> one wall where all the joists come in at 90 degrees to
> the wall, they (joists) rest on another equally sized
> wood member called the sole plate.  This sole plate is
> often wood and could begin to crush slowly under
> concentrated load points. I don't want to make it
> sound impossible, but with carefull consideration you
> can succeed and know that you have not sacrificed the
> integrity of your home and the new tank. Best of luck
> and keep us posted on your progress and findings.
> Thanks, Diana

A couple of 2x8s sandwiched together make an excellent beam
that you and easily support with 2x4, using 3 in the
fashion normally used to make a corner is wood frame
construction housing.  Sandwich two together with a little
bit of plywood inbetween and the sandwich will be the same
width as a 2x4, which you can slap onto the top of the
sandwich boards.  A pair of those posts will support a pair
of sandwiched 2x8s.  Assuming you tank is near the wall,
half the tank weight is being shed to the wall suporting
the joists - the other half is going onto the 2x8 beam and
from there to the posts.  Now the rest of your floor can be
treated pretty much as if no addded load had been put on it
- roughly speaking.  This also assumes you have the tank
placed perpendicular to the joists.

Without reinforcement, you can expect a large tank to
defelct the joists, not enough to cuse failure in most
floors, but surely enough to make leveling the tank a real
pain in the neck.

I went to the trouble of speaking to a structural engineer
to get this info.  Goodness knows I wouldn't count on this
info if *I* had dreamed it up.

Scott H.

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