YourHomeCanada says a company named Modular Additions is busy adding modular second storeys to many of the pre- and post-WWII bungalows that dot Toronto.  Owner Vadja Jericevic says there are about 13 basic designs among the 70,000 bungalows in Toronto, and he has drawn up plans for each that can be easily adapted.  He typically does 30-40 each year, but this year demand has increased.  The City of Toronto issued 600 permits five years ago, and 993 last year.  Total costs run from $180 a square foot up to $200 and more, depending upon the options and aesthetics desired.  In some cases, homeowners have to upgrade their heating/cooling systems, but foundations are adequate to support the added weight.  As with modular homes, completion time is shorter than site-built, but occupants do have to vacate for several weeks.