Sharing Spaces

The rules that arise from a "communal" living space, a living situation where two or more people share a space are contingent on those living in the space and the restrictions that are outside of their control.  In my current living situation, there are two layers of rules, the explicit rules that are set in place by our landlord, and the rules that my housemate and I tacitly agree upon. 
The explict rules are usually uncontested and fair.  They are those that were initially outlined on our lease agreement and include things like not having pets, being responsible for paying the rent on time, and taking care of general maintenance duties. 
The implict rules fall under courteous conduct for the most part.  Since my housemate and I are good friends we usually split the chores and expenses, go in our rooms to have telephone conversations, and host guests after asking or notifying the other person.  What makes our implicit rule system function so smoothly is that we know each other rather well and are similar in our preferances for a comfortable and enjoyable living situation.  In a case where we had different ideas about what made a good living space, this implicit rule system would be much less likely to function well.  Because we agree on the implied rules, they seem fair. 
The criteria by which we evaluate these rules are comfort, safety, openness, respect, and fairness.  Most of the rules set in place by our landlord and those that we tacitly enforce are subjected to this kind of catagorical analysis.  If a rule seems like it infringes on of those expectations we begin to question its functionality and necessity.