joist loading

We are installing a new whirlpool bath in an older home, upstairs. The joists are probably fir (ca. 1900), a real 2x11, 16" oc, spanning 15 feet. Being conservative, I give the tub, loaded with people and water, 1700 lbs / 16.5 sq feet. (103 lbs / sq. ft) Location is adjacent to outside bearing wall, which is 16" granite.
Will we end up in the kitchen below? How might we reinforce the floor to prevent this?
Paul
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I have a two story garage, the second floor garages two heavy vehicles (Mercedes MLs) and is supported on 2x10s on 16" centers spanning 9 feet between steel beams. Your true 2x11 members have a little over 2x the load carrying capacity of a 2x10 (1.5x9.5). Even though your span is longer I don't think you'll have any problem if the members are in good condition.
RB
E. Paul Wileyto wrote:

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It is a common misconception that cars represent a significant load in a structure.
My little car weighs 2200lb and is about 13x6 feet or about 78 sq. ft. While it is approximately four point loads of 550lb, the average load is only 2200/78 = 28.2 psf. This is far less than the 103 psf that the water-filled tub represents.
If we assume a 6000lb vehicle that's 15x7, then the average load is 6000/105 = 57 psf. Don't forget that one foot of water depth represents a 64 psf load.
Best advise - if you're worried, contact an engineer; if you're not worried, make sure your insurance is paid up.
Mike
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