What is the most expensive part of renovating a house?
Structural and mechanical changes burn budget fastest.
Quick answer: Structural changes, utility relocations, and HVAC/electrical/plumbing overhauls are the priciest parts of most renovations.
In renovations, the priciest work happens before you see pretty finishes. Moving or removing walls triggers engineering, permits, and new beams. Replacing HVAC, wiring, or plumbing stacks labor hours and inspection fees, especially in older homes that need full upgrades to meet current code.
Hidden issues push costs fastest: rot, termites, asbestos, lead paint, or failed foundations must be corrected before continuing. Shifting kitchens or bathrooms multiplies expense because plumbing and electrical need rerouting through finished spaces.
Budget-heavy items
- Structural changes: beams, posts, headers, and new footings.
- Utility relocations: moving drains, vents, gas, or panels.
- HVAC redesign: resizing ducts, relocating equipment, adding returns.
- Remediation: asbestos/lead abatement and mold or moisture repairs.
Finishes still matter, but they rarely exceed the combined cost of structure and systems. Keep scope tight: leave kitchens and baths in place when possible, reuse existing chases, and hold 10-20% contingency for surprises.