Micro-apartments will be convertible. In the U.S., tiny housing units haven't yet achieved widespread acceptance, and the legislation allowing them in many cities has only recently been passed. Just in case the trend is a passing fad, developers are hedging their bets on micro-housing, the report found. Many buildings are designed so that micro-housing units can be easily combined into one- or two- bedroom apartments if demand decreases. Load-bearing walls, utilities, and other systems within the building are designed so that side-by-side units can be cheaply converted into bigger apartments.