my contractor is installing a new bathroom window for us as part of a whole house remodel. the window is a little larger than the last, so he cut a little bit bigger hole in the wall (didn't reframe) and slid the window in. he has put some form of flashing on the outside but there doesn't appear to be any flashing or waterproofing inside. we are in an extremely rainy climate.

every time I've seen a window installed, and when I installed one in a shed I built, there has been a black waterproofing tape that wraps around the inside of the window frame before the actual window goes in.

can it be put in after? does it need to go in at all? you can see a small gap to the outside, which I assume can be caulked shut, but I'm still nervous that a step has been missed.