Offsetting a shower drain trap?
A friend is having a shower installed in a second floor bathroom, directly over a stairway landing. The floor joists are only 4" deep, such that a trap under the shower would protrude into the head space in the stairwell. The plumber gave two options: raise the shower floor four inches, such that people using the shower would have to step up roughly 8 inches into a high shower floor, or to offset the trap for the shower drain about 18 inches away, in an area where the floor joists run 10 inches deep. He said that a building inspector told him he would okay the offset trap, but I've never seen it & my friend is afraid the plumbing won't pass inspection. So the question: is a trap ever okay set away from the drain opening of a fixture?