Sally
When you say condensation do you mean in the bathroom or throughout the house? No it is not normal for the GIB to act like that if it has been properly sealed when it was painted. You should ask the builder to look at it. If you mean in the bathroom then I would suggest they have used the wrong type of paint – again builder should have a look. If it is their subbies who have not sealed/painted properly then they should go back to them and get them to sort. Good luck 🙂