How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
Can I use Tyvek as a belly wrap replacement for a mobile home?
Tuesday, September 11, 2018
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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