Sounds like a room bound issue. If you copied a vanilla cell, and added anything to it that is outside the room bounds, then it will not render correctly in game.
To check if this is the issue, load your mod in the CK. Open your cell in the render window, then on the task bar, click view, click Show/Hide Window, tick portals and rooms. If a large blue box appears around part of your cell that is the room bound and anything outside of that box will not render in game. To solve it you can either delete the room bound or create new ones with portals connecting them. http://www.creationkit.com/Room_Bounds_and_Portal_Basics explains what they do, and http://www.creationkit.com/Bethesda_Tutorial_Optimization explains how to create them.
Hope that answers your question.
i haven't got any markers or portals. only the door that links it to the outside world. theres no big blue box or anything.
i'm not really sure what a vanilla is (i don't have any Vanilla mods if that's what you mean?)
once i try to get inside the house in game there is only the half the house as well. theres nothing to run into so the objects are litterally no longer there and i can fall through the empty spaces and re-spawn
hopefully this link works. here's some pictures http://sta.sh/219w83v1q1ip?edit=1
ahh i've figured it out!
i wasn't setting my plugin as the active file!