Mobile Homes: Vapor Barrier Vs Vapor Barrier

By
Home Inspector with King of the House Home Inspection, Inc

Mobile and manufactured homes have some oddities of construction compared to stick-built homes. One of those, that is often misunderstood, is the issue of the "vapor barrier." Under a conventional home, everybody knows what we are talking about when we discuss the crawl space vapor barrier -- the plastic sheet over the soil.

At a manufactured home, the structure the units rest on can vary from concrete blocks or steel posts on soil with no footings, to blocks on gravel with or without footings, to a concrete slab, to ribbons (concrete strips) that serve as footings for blocks or posts. There should be a bottom board up under the floor of the home. Now, this goes by various names. I have talked to mobile home professionals about this terminology and here are some of the words they use for this barrier: Road barrier, Rodent Barrier, Vapor Barrier, Bottom board. Often, due to past repairs, this undercarriage barrier is cut, not properly repaired, so hanging down.

A misconception with some people is that this bottom board replaces the need for a traditional vapor barrier on the earth. In my experience, usually that is a dangerous assumption for the longterm condition of the home. Now, if the home is up on a neatly poured slab, and that is on a plastic sheet, I think they are okay. But with the other configurations, there is exposed soil. That exposed soil allows moisture to evaporate up. Their thought is "so what" it will be caught by the bottom board and the frame is steel. But think about it, steel rusts and over time rust can put holes in metal or turn it to brown powder. A main cause of high relative humidity in a home is a wet crawl space. Some photos, to illustrate my points, are below.

 

No conventional vapor barrier on the soil at this mobile

 

Condition of bottom board

Moisture on the steel frame and heavy rust

Thanks for looking.

Steven L. Smith

Bellingham WA Home Inspector

 

Posted by

        

        

Check out "This Day In History" -- music and vintage television from the 1950's through the 1980's.  I enjoy writing these articles because they take me back to my days in radio broadcasting. Click on Elvis' gold record, below, to revisit those golden hits of yesteryear.

           

close

This entry hasn't been re-blogged:

Re-Blogged By Re-Blogged At
Spam prevention

Accessibility option: listen to a question and answer it!

To submit the form,
drag the car to the circle on the side.

Type below the answer to what you hear. Numbers or words, lowercase:

Topic:
ActiveRain Community
Tags:
mt vernon home inspection
mobile home
anacortes home inspector
bellingham wa home inspector
bellingham home inspection

Comments 2 New Comment

Rainmaker
267,519
John DL Arendsen
Real Estate Broker, Mfg Home Dealer, General Contr
TAG Real Estate Sales & Investments & ON THE LEVEL GC

I'm way late for this one but it just popped up on my radar so here goes anyway. 

Please feel free to log onto our Truliahttp://www.trulia.com/blog/onthelevelcontractors/ or Active Rain bloghttp://activerain.com/blogs/johnarendsen for more comprehensive information about the MH Industry. 

Or you can check our our website and give us a call or drop us an email. We are RE Brokers, Manufactured Home Dealers and licensed, bonded and insured General Contractors and have been actively engaged in the MH Industry statewide for almost 3 decades. 

We love to Network with other MH Professionals.

February 27, 2011 04:23 PM
Rainmaker
267,519
John DL Arendsen
Real Estate Broker, Mfg Home Dealer, General Contr
TAG Real Estate Sales & Investments & ON THE LEVEL GC

Steven, I'd love for you to join our group. You have a lot of knowledge about the Manufactured Home Industry that could benefit our group and we invite any of your contributions.

http://activerain.com/groups/manufacturedhomes

January 31, 2014 10:54 AM
Rainmaker
1,172,496

Steven L. Smith

Bellingham WA Home Inspector
Ask me a question
*
*
*
Spam prevention

Accessibility option: listen to a question and answer it!

To submit the form,
drag the car to the circle on the side.

Type below the answer to what you hear. Numbers or words, lowercase:

Additional Information

Steven L. Smith, King of the House Home Inspection, provides information for real estate buyers, sellers and real estate industry professionals. Blog posts emphasize issues commonly found in Bellingham, WA and Whatcom County. Smith is Washington State Licensed Home Inspector #207, a state licensed structural pest inspector, ASHI certified inspector #252760 and one of the most experienced inspectors in the northwest corner of the Pacific Northwest. Steven L. Smith is lead instructor of home inspection at Bellingham Technical College and teaches classes for Washington State University and the Washington State Department of Agriculture. Steve was a two-term member of the state licensing board.