Why is it a dangerous mistake to attach a carport, porch, or room addition directly to the roof of a mobile home?

Tuesday, May 14, 2019

When the roof structure of an addition is attached directly to the roof of a mobile home, failure of the addition under the uplift force of high winds will often strip off the roof of the mobile home and cause other major damage to the home. Here’s couple of examples documented by the Federal Emergency Management Agency (FEMA) in a 2007 report on the performance of mobile homes in “high wind events."

    Here’s what the FEMA report says:

"The potential for damage to manufactured homes increases significantly when additions like carports, awnings, or porches arefastened 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."

    Mobile homes are not ordinarily engineered and manufactued to accept any additional loads on their walls, so there are two ways to correctly install an addition to a mobile home:

  1. Have the manufacturer install a “host beam” in the wall framing of the home when it is built and specify piers and tie-downs rated for the added load imposed by an addition, but both by gravity and windstorm uplift, so that is ready to accept an addition. To learn more about this option, see our blog post What is a "host beam" at a mobile/manufactured home? Or, if your home was not pre-engineered for an addition, then...
  2. Build the addition as a freestanding structure, not bearing on the walls or fascia of the roof of the mobile home, and install a flashing to connect the old and new roofs. Here’s an example below.


    And an example of the wrong way to do it.

    Also, see our blog post What do I need to know about building an addition to a mobile home?

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

How do I find out if a manufactured/mobile home has been moved from its original location?

 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? 

 Can you put a zone 1 mobile home in Florida?

 How can I remove water under my mobile home?

 What's the differences between a trailer, a mobile home, a manufactured home, and a modular home? 

 What is a D-sticker mobile home? 

 What are the tie-down requirements for a mobile home?

 How fireproof is a mobile home?  

 Can I install a mobile home myself?

 What is a Park Model mobile home?  

 Does an addition to a mobile home have to comply with the HUD Code? 

 What walls can I remove in a mobile home?

 What can I do to prevent dampness and mold in my mobile home? 

 How can I tell if a mobile home is well constructed?

 How can I tell the difference between a manufactured home and a modular 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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