Bathroom renovations cost more and take longer than expected because bathrooms contain more mechanical systems per square foot than any other room in the house.
Scope Definition
A cosmetic refresh might cost $5,000 to $15,000 and take 2-4 weeks. A full gut renovation can run $40,000 to $100,000+ and take 3-6 months. The difference is almost entirely whether plumbing and electrical systems need to be moved.
Ventilation
An exhaust fan that moves at least 1 CFM per square foot of bathroom area is the minimum standard. The fan should run for at least 20 minutes after a shower to fully clear moisture. A humidity-sensing switch eliminates the forgetting factor.