We've all been there. One of your flatmates gets a new girlfriend, and before you know it, you're seeing more of her than you do of him. Of course, it happens the other way round too, with boyfriends often hanging out on the sofa, using all the hot water, or making a mess in the kitchen.
When a flatmate's partner is spending more and more time in your flat, things can become a little tetchy. After all, you're paying your fair share for the living space, the kitchen, and the bills, and suddenly you find yourself with a new unofficial flatmate who's taking it all for granted. So what should you do?
It depends how much time they spend in the flat. It's the general consensus that if they spend more than half the week there, your flatmate's girlfriend or boyfriend should start contributing to the bills.
If they don't offer a contribution towards their share, you should think about asking them (or bring it up with your flatmate first). Good flatmates need to be honest with each other about their expectations and, if you feel that this flatmate has broken a rule, unwritten or otherwise, you should be upfront about it. Find a time when all the flatmates are around to talk it through together.
If the boyfriend or girlfriend has more or less moved in, you should consider making a change to the current tenancy agreement, to formalise the arrangement and make sure the rest of you aren't left out of pocket.
Of course it's not just about money either. The extra person is taking up some of your space and affecting your privacy.
The solution always lies in good communication. Address the situation openly and try to find a compromise. The flatmate involved should try to consider your point of view, and, if an agreement can't be reached, you could suggest they move out, find a place of their own, and you could then find a replacement flatmate who fits better with your style of living.