Night time accidents

Question
Hello, I have an 8 month lab who had grasped the idea of no toilet in the house at night for months until I gave her access to the whole of the hall. Originally I had shut off the corridor at one end which stopped her from getting to the main square hall. She seems to think it is ok to do her business by the front door and now does it just about every night. This is not a door we use so she has never gone out this door but it is badly fitting with a draft underneith. How can I stop her doing this ? Please help I am desperate.

Answer
If confining her to a small area was working, go back to it.  Activity stimulates elimination.  Giving her more space may lead to more activity and having to eliminate.  More space may also give her a chance to chew things that she shouldn't.  

If she isn't spayed, it could be part of the flaky behavior preceding coming into season.