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site-built, mobile/manufactured and modular homes

What do I need to know about building an addition to a mobile home?

Friday, August 10, 2018

Here’s our list of ten things to consider before starting an addition to a manufactured home:

1) There are two types of additions to a manufactured home. Decks, covered decks, screen porches and carports are examples of the first category, that do not create an enclosed and conditioned (heated and cooled) living space. These additions are less expensive to build and easier for a homeowner to tackle as a weekend-warrior project.

   Bedrooms, bathroom, family room, or any other enclosed and conditioned space are the second type. They are more complicated and expensive, and need the services of an electrician and possibly a plumber and air conditioning contractor. 

2) Also, while any addition—even a deck—seems to require a building permit nowadays, adding conditioned space will require building plans and compliance with multiple life/safety building code requirements. Adding conditioned living space is a serious project, and usually ends up costing more and taking longer to complete than you initially expected. A poorly done addition may actually decrease the curb appeal and add little to the resale value of the home, like the first photo below, or leave a passerby saying “what-in-the-world-were-they-thinking,” like the second one.

3) Are you considering moving your mobile home sometime in the future? While less than 10% of manufactured homes are ever moved from their original site, if you think you might be relocating it you should know that any addition must be demolished as part of the move and makes the process more complicated and expensive. 

4) Although an addition can meet the walls of a mobile home, it cannot bear on it and should not be fastened to it. The State of Florida Admistrative Code (5C-2.0081 Mobile/Manufactured Home Repair and Remodeling Code) specifically prohibits it. Most manufactured homes and foundations are designed only to support itself, and any additional load imposed on the walls or roof structure will exceed the engineering parameters. An addition, even a deck next to the home, must be self-supporting.

    The series of photos below, of an addition in progress, shows where they got it partially right—and part wrong. Photo #1 shows that the wall framing meets the mobile home walls, but does not bear on them. That’s good.

    But the roof panels of the addition in photo #2 bear on a channel bolted to the wall of the home, which transfers part of the roof load to the mobile home, and is a no-no. Installing a beam that is separate from the mobile home wall, like in photo #3, is the correct solution.

    The only exception to this rule is when the manufacturer installs a “host beam” inside the wall specifically for an addition at the homesite, such as a carport. See our blog post What is a "host beam" at a mobile/manufactured home? to learn about them. Also, click on the image below to download a bulletin that Collier county (located at sothern tip of Florida) issued after hurricane Irma hit in 2017, which explains repair and remodeling requirements for mobile homes along with quoting the state code.

5) Here’s what a 2007 study by the Federal Emergency Management Agency (FEMA) of the performance of a mobile homes with an addition in a hurricane or tornado determined:
    “The potential for damage to manufactured homes increases significantly when additions like carports, awnings, or porches are fastened to the home. These additions concentrate wind forces where they are fastened to the home. The increased forces can overload connections used to hold the home together and cause failure of the members or connections in the home.    Most home manufacturers prohibit attachments to their homes unless special provisions to support attachments were incorporated into the home when it was manufactured. The attachments themselves, unless engineered, also violate local code requirements in many jurisdictions.”

6) Bedrooms are required to have a means of egress—a way directly out of the home in the event of an emergency such as a fire. This can be a window, door, or sliding glass door, and all bedrooms in a manufactured home comply with this code requirement. If your home addition eliminates the only window in a bedroom, then it is no longer allowed to be used as a bedroom. While you might choose to do so anyway, when you sell the home it may not be counted as a bedroom by the realtor or appraiser.

7) Mobile homes are required to have two exit doors to the exterior, with no lockable doors between the bedrooms and each of the exit doors. If you decide to use the secondary exit door as the entry to your home addition, then the door must be removed and converted to a cased opening, or  have a latch set (doorknob that cannot be locked) installed, to create a route that leads directly to a new exit door to the outside. 

8) Some mobile home parks do not allow additions, and the rest have restrictions as to where an addition can be placed on the lot and how it is constructed. Also, the local building department will have jurisdiction over any additions on private property or in a park. Check for requirements first, before you make any plans.

9) A mobile home is built on a one-piece steel I-beam frame and reacts to any heaving or settlement stresses from the ground under it as one unified structure. Most manufactured homes are installed on a temporary foundation of stacked blocks over a plastic or concrete pads which, when combined with adequate tie-downs, are an acceptable foundation system. But any addition is essentially a detached structure, and will react differently to foundation movement. Problems at the marriage line of an enclosed home addition can occur over time, and one of the advantages of doing a deck or porch addition is that it does not have to be attached to the manufactured home.

1) The addition should fit in with the look of the mobile home, and connect visually in a appropriate style. Any addition that does not resemble the main home will not add value to your property and annoy the neighbors.

   So, after everything is considered, you might reach the conclusion that an addition of conditioned space to a mobile home in not such a good idea. Unless you desperately need more interior room, we suggest tackling a deck, porch, or interior remodeling instead. But, if you still really want to build an enclosed addition, get a copy of the manual “Manufactured Home Additions & Roofed Decks,” by L.J. Wright (Birch Lane Books, 2004).
It’s available from Aberdeen Parts Store, (605) 229-2627, or online at It has step-by-step instructions, diagrams and photos to help you understand the right way to build an addition.

    Also, see our blog post Does it make sense to buy an older mobile home and remodel it?

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Want to learn more about inspecting
manufactured/mobile homes? 
Get our  Handbook for 
Manufactured Home Inspectors 
at for $19.95

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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED HOMES:

Where can I file a complaint if I have problems with my new or used manufactured/mobile home in Florida?

 What are the most common defects in mobile/manufactured home foundation piers?

How do I determine the age of a very old mobile home?

What is a "HUD label verification letter" for a mobile/manufactured home?  

When did a ground cover vapor barrier (plastic sheet) become required under a mobile/manufactured home? 

Is it safe to go under a mobile home? 

Are older mobile homes unsafe? 

What do I need to know about buying a foreclosed mobile home? 

Does it make sense to buy an older mobile home and remodel it? 

Where do I find the vehicle identification number (VIN) on a mobile home? 

How do I find out how old a mobile home is and who manufactured it?

What is the right price for a used mobile home?

How energy efficient is a mobile home?

When were the first double-wide mobile homes manufactured?

How do I upgrade my old (pre-1976) mobile home to meet HUD standards?

What size air conditioner is right for my mobile home? 

Can you move an older mobile home in Florida? 

What does the HUD tag look like and where do I find it on a mobile home? 

       Visit our MOBILE/MANUFACTURED HOMES  page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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