For years we have had factory built homes where the entire home was built in a factory and then trucked to a site and put on a foundation, much like a mobile home. When people wanted larger factory built homes, they started making them in two halves, to fit on the trucks, and stuck them together on site.
Other manufactures have manufactured wall sections to speed construction, arriving on the site with a truck full of walls that go up quickly and then the roof, windows, doors and siding go on afterward.
In this show we found someone who has combined these two ideas. A company, in Toronto, called Modular Home Additions, makes factory manufactured custom second floors. The idea is actually simple. They measure your house and work with you on a second floor plan, including where to put the stairway. Then they go away and build it all in a nice warm building where people can get everything right without either the products or the workers freezing or getting rained on. In fact, the factory is right in a heavy residential area of Toronto so they don't have to truck the final products very far. The walls have the windows and doors, as well as, the siding installed before leaving the factory. The roof is mostly shingled. The inside is totally unfinished, just bare studs.
Then they show up at your house. Day 1, they cut the roof off and install a full span floor right over the old ceiling joists. That means the floor is not resting on first story inside walls, leaving you lots of future options with your new house. Day 2, they install the walls and finish off the siding. Day 3, they install the roof and finish off the shingles. OK, the project on the TV show took 5 days, because they ran into an unusual supporting outside wall, but even 5 days is pretty good. This couple had decided to put a temporary stairway up to the second story patio door and not cut out the indoor stairway until, over the winter, they had slowly finished all the second story themselves.
They had total access to their old house throughout the 5 days, apparently even taking showers while the roof was disappearing. The idea is to get the structure up and closed in, as quickly as possible. You can do or have done the rest, at your own pace. This company has really found itself an interesting niche market, dropping second story niches down on houses so quickly that the homeowners tend to drive past their old house because they don't recognize it.