One example is allowing the construction of ADUs. Throwing a small apartment on top of a garage is an extremely common addition these days that requires minimal waste.

Similarly even without ADUs, many homes in my neighborhood just outside of Boston have been remodeled from single family 5 beds to 2/3 family condos without being completely demolished. This was largely made possible by eliminating rules and regulations like the parking requirements for houses near public transit and loosening restrictions on conversions themselves by reducing restrictions for setbacks and similar rules. My own home is a condo conversion and it’s the only reason we could afford to own here.