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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
By floorjacks, I am thinking you are talking about adjustable steel columns? These are put in to carry the load of the beam above. They are based on the size of the beam, and the load placed on that beam. So there is no set number of columns. If you really want to find out, hire a structural engineer to come over and take a look.