NoneA basic rule of thumb for modular homes is if it can be built on site, it can be built in a factory and one story modular homes are no longer the only ones available. Two story modular homes and even some three story homes are on the market and as more home buyers demand more space, the chances are modular homes will continue to grow to meet the demand.As pre-fab housing, as they initially were called, hit the market they usually consisted on one story buildings with similar cookie cutter style appearance. It was fairly common that one wall from one house would fit another house by the same manufacturer. Times changed and demands changed and the builders changed to meet the demands.Many two story modular homes are being lived in today, along with mansion style three story modular homes. When people finally caught on that modular homes were usually of a better quality then sit built homes, they clamored for more choices in styles and size. Executives did not want to give up their lifestyle and spacious homes in trade for the modular home quality.When banks and traditional home mortgage lenders finally realized that modular homes were not the same as manufactured homes, also referred to as mobile homes or trailers, mortgages for modular homes became easier to obtain and the boom was on for modular housing.With the stigma of pre-fab replaced by the known quality of modular housing, more interest was shown and more people wanted the additional space a two story modular home provides. Architects got in on the act, designing large spacious homes and to maintain their edge in the home building business, modular home builders adapted and began to build two and three story modular homes.Larger and more technology-dependent factories began to go up to meet the demands of the larger housing units and more efficient, quality-conscious inspection methods were developed. Some factories, now over 200,000 square feet can build a modular home in under two months where it could take up to six months to build the same house on site.Getting a stronger more durable two story house in about half the time it would take for a site built house has generated a lot of interest in the modular home business. Being able to buy it for less money is a bonus for the homeowner. Additionally, since they are built in a controlled factory environment, they are generally more energy efficient than site built homes adding to the savings realized in buying a modular homeAdditionally, for the price to approach the cost of a site built two story home, additional options and amenities can be added to the basic cost and possibly still be cheaper. Options like stone countertops and better quality carpets can be purchased without pushing your budget to the limit.With the growing interest and acceptance of modular home, especially in the two and three story designs now available, there are few limitations placed on home designs by the modular home building industry.