Expert: Roger Zona - 6/3/2009

Question
QUESTION: I wish to put a 600 pound safe in my first floor residential office. The footprint is 720 sq ins or 5 sq ft. This is 120 lbs/sq ft. I have 2 by 10 joists on 16 in centers and the span is 14.5 ins. I plan to set the safe on the outside wall where the joits sit on top of the concrete basement wall (where it is strongest). I think this will be OK. Agree?

ANSWER: Hello Dave,

Don't forget, you will probably put papers and such in the safe so the total weight will exceed 600lbs.  

But, that aside, typically a residence is designed with a 30# live load and approx. 60# dead load.  That doesn't make the grade but it probably would be OK since, as you said, putting the load above the exterior wall would be a better position.

To provide a safety factor, I suggest you reinforce the floor where you intend installing the safe.  The joist span is typical and I assume the 14.5 is lineal feet.  Again - very typical.  You could add two more joists - installed either side by side with the existing joists or split the spacing with joists to 8" o.c.  Either method would be acceptable and would redistribute the load.

Question - why not put the safe in the basement or perhaps your garage.  I suspect you wouldn't be in the safe everyday.  Of course getting the safe down stairs would be a task for four men and a boy!

I hope this has been helpful.

Roger

---------- FOLLOW-UP ----------

QUESTION: Thank you so much Roger. What are the units for 30# and 60# ? 30 lbs per what ?  Also, I have seen it stated somewhere that the dead load was around 10#. Please confirm your 60#. Did you mean 6#  If I put it in the garage, it will be too easy to steal with a pickup and if I take it to the basement and my sump-pump fails and I have a foot of water on the floor that's no good either. Here is yet another example of "the more you have, the more problems you have". Thanks again Roger.

Answer
Hi Dave,

My mistake - a typo error.  You are correct, the dead load I meant is about 6#.  All weights are calculated as per square foot.  

If you add two joists the load numbers will change to the approx. load weight you have - 120#/sf.  The dead load will increase to about 10# but that isn't a factor in this instance.

Hope this wasn't an inconvenience.

Roger