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Re: Floor Suport and Tank Weight

This is late but, floor loads is a complex business and little useful
info is available.  I condulted a buidling engineer but most folks
don't have that option -- at least not affordably.

James wrote:
> "A 90gal is about as heavy as most folks can safely go
> on a wooden joisted main floor(of course there are
> always exceptions,depending on era,local code,etc)...I
> would have loved to have gone for the 48"x24"
> 125gal,as opposed to the 48"x18"90 gallon I "settled"
> for....but I was too scared of my tank ending up in
> the suite below mine :)"

Failure probably wouldn't happen, but you wouldn't want to put  a lot
of other load on the floor plus the tank.

Tom Wood wrote:
> Most modern structures are designed for a live load of 150 pounds per
> square
> foot. A 90 gallon weighing 900 pounds with a footprint of 48" x 18"
> imparts
> a concentrated load of 150 pounds per square foot. A 125 gallon
> weighing
> 1200 pounds with a footprint of 48" by 24" imparts a concentrated
> load of
> 150 pounds per square foot. But most of the floor area doesn't carry
> a full
> load of 150 pounds per square foot over every square foot of area,
> although
> theoretically, it could.

A large refrigerator can easily exceed 120-150 pounds per square foot
and no one worries about floor failure from these, not even the
building inspectors.  The 120-150 pounds per square foot, live load,
figure is for total floor loading, and assumes loads will be
distributed around the room.  It is not a factor or limit for
concentrated loads.  The important factor for concentrated loads is the
"Stress in Bending" factor.  the formulas for figuring the Stress in
bending values are complex -- consult an engineer.

But super-simplified:  different lumber has different strength when you
load it.  Some starts to bend before others; some starts to crack and
fail before others.  It depends also on the thickness and depth of the
joists and how many are directly supporting the load.  A tank placed
parrallel to joists will probably sit over only one or two joists.  And
it all depends on how long the joists are!  The longer the joist, the
more it will bend -- there is more give or bounce in a long board than
a short one -- try standing on a long and then a short plank and you'll

In most homes built to modern building codes, a 150 gallon tank can be
supported by the floor if the tank is placed perpendicular to the
joists and the joists are 2 x 10 inch fir or better, spaced 16" apart
center-to-center.  But not much more concentrated weight should be
added to those joists -- don't put a half dozen 150 gal tanks in the
same room on those same joists.  And bracing from below would be good
but not necessary.  With adequate bracing from below, you could
essentially forget about the weight of the tank -- so to speak -- and
fill the room with 150 gal tanks.

Scott H.

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