The 30 percent rule is a general real estate guideline suggesting that a homeowner should not spend more than 30 percent of their home’s current market value on renovations. The rule is a rough benchmark, not a law, and it is most relevant for owners planning to resell within a few years. For clients renovating to stay long-term, Custom-tier features often justify going above the 30 percent line because the value is in daily use, not resale.