The easiest way to enlarge your mobile home is to purchase a modular room addition. The setup includes marrying it to your current foundation and roof.
Check zoning codes before you begin the project. If you live in a rural setting, zoning may not be an issue. Owner-built mobile home room additions are not HUD compliant and, therefore, not legal. Your room addition could void the warranty. Also, if you ever decide to sell the home, it will not pass the specs.
How to Add an Extra Room to a Mobile Home. You may discover that your mobile home that is just too small, and you might consider trading up. If you think, however, that a completely new home is too expensive, you can add an extra room to your existing mobile home.
Decide what you want in the room. Basic considerations include matching colors and materials, installation of heat and air extenders, electrical outlets and window additions.
Search for companies that build modular rooms to attach to your mobile home. See Resources below for a good website at which to being your search. Remember to discuss delivery and setup charges before going too far into the conversation.
Take pictures of your current home and discuss with the building company the changes you want to make. You will probably have several phone and email conversations, including sending the pictures to the building site.
If you are handy with tools, you can consider building the room addition yourself. Ask mobile home manufacturers where to get your materials. Home renovations retail sites should have information you can use. You can use outside help for systems work like the heat and air conditioning venting.
Build the room walls starting with the framing. Dry them in, adding your Sheetrock.
Put on the roof. Take pictures of the existing roof so when the time comes to seal the roof at the attachment, you know what you're getting into. Expect to use flashing.
Go back in and finish the interior walls with paint or wallpaper.