We cannot say for sure what the most expensive thing is when renovating a house. However, the cost of a renovation will vary depending on the size and scope of the project, as well as the materials and finishes that are chosen. Running Renos offers free in-home consultations, so you can contact them to get an estimate for your specific renovation project. Here are some of the factors that can affect the cost of a renovation: The size of the project: Larger renovations will cost more than smaller ones. The scope of the project: A complete kitchen renovation will cost more than simply replacing the backsplash. The materials and finishes chosen: High-end materials and finishes will cost more than lower-end options. If you are considering a renovation, it is important to get estimates from a qualified contractor before making a decision.