The House Chamber was obviously fitted with bathrooms at a time when only men were representatives. I am actually shocked to find that while the men's restroom is very close to the chamber, a restroom for women is a long walk away. I don't think we have to gut the building to fix this.
From what I saw there, it is very difficult to move anything without major historic significance. I understand they redid the senate bathrooms recently.
Even if they trade bathroom space for hallway space, they impact upon the tile and the frescos in the ceiling. or even the view of a long hallway.
http://clerk.house.gov/histHigh/Virtual_Tours/index.html