Expert: Bruce E. Johnson - 10/8/2011

Question
QUESTION: I was presented with a opportunity to receive a 125 gallon reef aquarium for free, but I had to get it quickly. I had owned one before at that size in a different location so I wasn't to concerned with the weight. I looked under the house and picked a place that seemed to be the must supported. Moving a fully stocked tank was a big undertaking and to keep everything alive in a small window of time things got a little rushed. In hindsite I would have placed it a little differently. So everything was very level and no unbalanced movement. Then three weeks later I started to see the tank move a little when some one would walk by it. I was concerned so went back under the house everything looks normal no bending or cracking. A few more weeks have past and the tank is moving more now when you walk by it only on the one side. I have been researching like crazy, and from what I have gathered the floor is deflecting. I am not to concerned with the floor as much as the tanks seals under that kind of movement. We are planning to move in a year so I don't want to invest to much in reconstruction. Would I be able to use some solid cinder blocks and metal shims to help support the floor in a few spots to help balance the weight. Do you have any other ideas that are not to costly. I appreciate your response.

ANSWER: Hi Lance, yes the cinder block idea would probably be the cheapest and easiest but instead of metal shims, tapered cedar shims and pieces of pressure treated wood can be used to make up the difference in height between the stacked block and the floor joist(s).  I say cedar shims or some other type of tapered wood or composite shim because as you drive the final shims into place the tapered part will exert more pressure on the joist and hold your support more securely in place and possibly reverse any deflection.  For a more permanent support and if you have tools available you can get precast concrete deck support blocks at Home Depot or Lowes.  These blocks have a hollowed out section in their middle that a vertical 4x4 fits nicely into.  You can slide the support block into place and then measure up to the joist and cut a 4x4 to length.  Then you will need a small 2pound sledge to drive the 4x4 up into it's vertical position, or if movement is limited cut the 4x4 slightly shorter to allow it to be set under the joist and then do the shimming technique to solidify the final support.  If the floor joists have settled to the point that they need to be jacked up a small hydraulic Jack set on stacked pieces of wood can be used to Jack up the joist prior to the installation of the support system you select.I hope this info helps please feel free to write again regarding this or other matters, sincerely Bruce Johnson..bejohnsonconsulting.com      

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QUESTION: Thank you Bruce for responding its very helpful. I have another question regarding as to how many supports I should use and should they be directly under the area of the tank or farther out.

Answer
Hi again Lance, if your tank is supported on four legs and each pair of legs is near a floor joist.i would  do those two joists first.  If the tank sits solidly on the floor with no legs or concentrated points of contact then I would find a couple of joists in the center and try them first.  If your tank sits parallel to the floor joists then I would  find the joists most directly under the tank and put the supports as close to the center of the tank as I could get. Since I don't really know how your tank is supported, if it sits on a stand or on a counter Or if it is near a wall or in the center of a room I really can't be much more specific.  But by looking at the floor system from underneath and determining where the tank's most concentrated load is you can best figure out where to begin your supports.  Obviously the closer the tank is to the mid span of a joist the weaker the joist will be so look for those spots to support first and see if shoring them up helps alleviate your problem and take it from there.  I hope this info helps p,ease feel free to write again regarding this or ore matters, sincerely Bruce Johnson ..bejohnsonconsulting .com