I wonder about the weight added to walls or floors supported by RSJs etc, when for example someone covers their bathroom in heavy stone or marble. I know the stucture is specified with lots of margin, but as things are added the margin gets whittled away. I added load to the existing RSJs at the back of the house when the extension roof was build. I had a struct eng to check out the extra loading and he was a bit iffy until I explained that the RSJs were not supporting the floor upstairs. He was happy when I showed the floorboard direction under the bath. I detected a couple of millimetres bend in the one that had a point load from one of the roof purlins. I guess thats OK ! Simon.