Forced appreciation is the value you manufacture yourself, as opposed to market appreciation you passively wait for. In small multifamily and commercial property, value is tied to net operating income (NOI), so any durable increase in NOI raises what the property is worth: bringing below-market rents up, cutting operating costs, adding laundry or parking income, or reducing vacancy. Renovations that let you charge more rent do the same.
The lever is powerful because of capitalization. At a 6% cap rate, every extra $1,000 of annual NOI can add roughly $16,000 to value ($1,000 / 0.06), which is why value-add investors obsess over operations. The catch is that it only works where value follows income. A single-family home is priced mostly on comparable sales, so forced appreciation there comes through renovation rather than an NOI bump.