What if the non custodial parent moves to a house ...

In terms of whether the child can visit the unfit house, yes.

This is another topic that make me sick.NON custodial parents are not the kids real parents and they are there to fill in and help the child but if they are not doing something that is right the primary custodial parents have to deal with the courts.They can't just say what should be done cause they have basically lost there rights as parents.The court can be the only ones to decides what is what.If the custodial parents have moved in a house that is unfit or living conditons are unfit then neither the custodial parents or the primary parents should have the kids.This is a topic that a lot of people deal with everyday.They have not done what they should have when they was sopost to be parenting now they got a lot to say about someone else parenting.In this case I think that both sets of parents should be given parneting classes and to know what is right for children living and wrong ways to live.

I disagree about Monica's reply, the non-custodial parent is still their parent and though the parent that the child resides with disapproves of the lifestyle of the noncustodial parent they must first reason with themselves by asking themselves:

Is this enviornment physically dangerous or unsafe? 

Is the non custodial parent capable and caring enough to ensure their child's safety? 

If you think the enviornment is unfit for some other reason than ask yourself does it pertain to your beliefs as to why you have deemed it to be unfit? Because if it is your values that are at the root of your concern and cause you to view the enviornment unfit, your concern may be more self serving than actual concern.  Remember that your child needs and deserves both of their parents, and if custody is split between two homes, then it is going to be likely that those homes will differ dramatically from each other, seeing that most people seperate due to irreconciable differences in the first place.