Yes. In the modular manufacturing industry, I've worked on designs and engineering for a number of builders that have done this. One builder on Long Island, NY had made quite a business doing just this.

Of course, first the internal structural support needs addressing, then the roof gets removed and plates or framing added as required to provide a level base for the modules. Usually the day after demolition of the existing roof, the modules are set and buttoned up.

The beauty of this method is the minimal amount of time the homeowner is displaced or inconvenienced while construction goes on above. Also the risk of weather damage to the lower floor is minimized by shortening the time span. It also puts on quite a show for the neighbors. (Plan a neighborhood BBQ for the day of the set. The neighbors will all be there anyway.)

Your biggest problem may be finding an authorized modular dealer in your area willing to tackle this project. It is not a very complicated process but requires quite a bit more time to carefully measure and document the existing conditions and engineer the structure.

Wayne

I did this to my regular house and it was a nightmare including water damage while the original roof was off the house. And we had problems finding a contractor to do it for us. Although it turned out great in the end.
Like the above person said - you may have a difficult finding someone who is qualified to tackle this job.
Good luck - let us know what happens!

Hi Wayne,
Could you possibly give me the name of the builder on Long Island that does this?

I am on Long Island and looking into doing an addition and would like some info.

Any ballpark idea as to the cost of doing something like this?

thanks,
Chris

We built UNDER our home. Added a full basement and doubled the s.f. At the same time, we turned it into a "regular" house as far as bank loans are concerned and it now qualifies for a normal lending agreement with lower interest. Had we done any other kind of addition it would still be considered a manufactured home.
The only thing left to do is to retire the title, which we will wait to do until we sell because according to the county assessors office, as long as there is a title to it somewhere they consider it a manufactured home and our taxes will be 1/4 of what our neighbors with homes not close to as nice as ours are. :~)

Chris,

Thought I sent this a couple of days ago. Must have forgotten to hit the "submit message" button.

I did some CAD work for this company some time ago. They did some nice work on the projects I was involved with.
If you contact them, tell them Wayne Morris sent you. (Never hurts to re-establish old ties.)

Wayne

Here is a link that might be useful: Builder Link

how long did it take to get the basement completed? and how much did something like that cost?