Clear house rules are important. But it’s naive to think that your rules, no matter how detailed, will cover every possible scenario. (I never ever would have thought to create a rule about no plaster heads in the oven!)

Eventually, issues are going to come up. 

That’s more or less inevitable. The key thing is how you handle them.

Most people don’t like conflict. Thus, when issues arise that they aren’t happy with, often their default behavior is to avoid the issue until it becomes unavoidable. By that point, they’re completely fed up and the other person has gotten comfortable doing the offending behavior. It’s a lose-lose situation for everyone involved. 

A far better approach is to address issues as they arrive. 

Sure, it will probably make you uncomfortable. But a little bit of discomfort now is much better than a lot of it later, wouldn’t you say?