That does not sound like a good idea. The belly wrap (also called belly board) that covers the entire bottom of a mobile home is typically polyethylene sheeting, which woven from black tapes of high density polyethylene and extrusion coated with a solid layer of low densityblack polyethylene coating. The coating makes it a VAPOR BARRIER. It is installed to keep the moisture in the soil under a manufactured home from rising up as water vapor into the floor framing and potentially causing wood rot and mold. Tyvek™, on the other hand, is a WATER AND AIR BARRIER, but is specifically designed to let WATER VAPOR PASS THROUGH. 

   When used as a housewrap on the exterior walls of a home, Tyvek™ (and any similar brand of flashspun high-density polyethylene fiber sheet) allows the moisture in the air that is generated by showering, cooking, breathing and other household activities to pass through the wall—rather than be trapped and build up inside the wall framing.   But you do not want water vapor rising up through the floor, so we recommend sticking with regular polyethylene sheeting as belly board replacement. The best quality belly board is woven from black tapes of high-density polyethylene that is coated with a continuous layer of low-density polyethylene that seals it.

   Tyvek™ is an amazing product, but this does not appear to be the right use for it. You might want to check with your mobile home manufacturer if you want a second opinion.  

    Also, see our blog post What is the plastic sheet called that covers the underside of a mobile home?

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

       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.