Your blanket condemnation of manufactured housing is disturbing. Where in the HUD code is the section that says the homes should be built inexpensively?
I own and maintain 38 manufactured homes. When I installed these homes I know I would be taking care of them for many years and selected most that were built quiet a bit better than to minimum standards. Manufactured homes, like most any product have some very high end producers and some junk builders. Most production homes fall someplace in the middle.
I live in a 1980's vintage Fleetwood doublewide that has a 1440 sq ft fully attached block addition. Most of my rental homes have one or more additions built onto them. The local building department requires sealed engineer drawings, showing how additions are to be added to manufactured homes. When the design is sound they have no problem granting permits.
My insurance company lets me to add value to each home that has an attached addition. We are in Central Florida and my homes along with their additions rode our three back to back hurricanes last season without as much as $500 damage to any one home.
You can visit the MH Parts Store OnLine
Select Exterior Additions from the menu of items on the left and you will see some of the ready made standard additions that most Do-It-Yourself types can add onto a home over a long week-end.
For more instant details about addition attachment, right here on our site, you can read Sealing an Addition
by MARK BOWER. Mark is the chief moderator for this repair forum and the owner of Aberdeen Home Repair. Mark is also recognized for his manufactured home repair lecture and consulting services. Additionally Mark has participated in Federal Government MH projects sponsored by both HUD and FEMA and he has been called as an expert witness in lawsuits that required a full understanding of the complex systems that make up the modern manufactured home.
There is a great article on our sister web site - www.MobileHomeRepair.com - that will explain more of the basics. Get the details By reading Adding on to your manufactured home
Denise - Talk to your local Building Department and a local Engineering firm to find out what the requirements for MH additions are in your area.