How old is too old for a roof, furnace or water heater?
Asphalt shingles last fifteen to twenty-five years, a furnace fifteen to twenty, an air conditioner twelve to fifteen, a water heater eight to twelve, and windows twenty to thirty. Anything within five years of the end of that range is a cost you are buying.
These are the numbers to price, not to worry about. Get a written quote for anything near the end of its life and treat it as part of the purchase price.
Roof: fifteen to twenty-five years for asphalt, longer for metal or slate. Look for curling, missing granules, and patching around vents.
Furnace: fifteen to twenty years. Past that, efficiency is poor and a heat exchanger failure is a safety issue as well as a bill.
Air conditioner: twelve to fifteen. Older refrigerants have been phased out, which makes repairs expensive.
Water heater: eight to twelve if owned. Check whether it is rented, because a rental contract is an obligation you assume, with a buyout in the thousands.
Windows: twenty to thirty. Failed seals show as fogging between the panes.
Add up everything inside five years of its end date. That total is a real adjustment to what the house costs you.
Next questions
What home maintenance do I actually need to do?
Seasonally: furnace filters and service, gutters twice a year, grading away from the foundation, dryer vent, alarms, and winterizing outdoor plumbing. Everything on that list is cheap and prevents something expensive.
Ontario
How much should I budget for maintenance every year?
Reserve against what the building costs to rebuild rather than against what you paid, which is how the ownership statement in this app sizes the line. Whatever figure you use, it arrives lumpy: nothing for three years, then a roof.
Market practice