We recently decided to remodel our upstairs bathroom (5 x 11 ft) and I have a lot of concerns about the amount of weight that will be added. I have had a contractor check it out and he says it should be fine, but I am still a little worried. I realize it is hard to give a definite answer based on the information I can provide, but I am more curious if I need to seek a second opinion.
Basically we will be adding around 1,100 lbs of stone tile to the back, sides, and top of the area around the bathtub. My rough estimates of the total weight when the tub is full of water and an adult is in it comes to around 900 lbs. Combined, that is approximately 2,000 lbs in the small area around the bathtub. Based on some research, the typical home is constructed (US) to support 40 lbs/ft. Using this value brings the total weight limit of the entire bathroom to around 2,200 lbs. So unless I am missing something, I feel as though this too close for comfort.
The bathtub is against an outside wall, as shown in the photo below. Also attached is a photo of the joists directly below the tub - note the black pipe where the drain comes down.