What is the plastic sheet called that covers the underside of a mobile home?
Thursday, October 4, 2018
It’s called a belly wrap, belly board, or bottom board, depending on who you ask. We most often hear it called belly wrap, but HUD and manufactured home industry associations refer to it as a bottom board. It’s a moisture barrier and also helps to prevent the entry of insects and rodents into the home—as long as the belly wrap remains intact. But when plumbing repairs require cutting open the wrap, sometimes the area doesn’t get resealed afterwards; or it get taped-up with some hardware-store type duct tape that comes loose after a few days.
Once an opening in the wrap is combined with a section of missing skirting, mobile home owners in rural locations have found that local small wildlife likes to pull down the insulation for nesting material, or just for fun, and drag it around, loose under the home. So a small opening in the belly wrap can become a big mess of shredded insulation and torn plastic sheeting strips in the crawl space.
Premium mobile homes have a netting stretched across underneath the belly wrap as a reinforcement, which prevents the gradual sagging between fastener rows that can occur over time. Large bulges in a belly wrap that is otherwise intact can indicate a plumbing leak under the floor. Cutting a pinhole in the bulge tells all.
We recommend patching any access hole cut in the belly wrap to make a repair under the floor of the home immediately after completion of the repair. A neat trick to simplify closing up the opening after your repair is to begin by cutting an X-shape centered under where you want to work. You will have four flaps hanging down during your repair that can taped back up when work is completed. Both mechanical fastening and a flexible sealant or tape should be used to secure the repair area.
The best repair technique is to install a sheet of lightweight sheathing within the belly opening above the hole, mechanically fasten (staple or nail) the torn area to the sheathing, apply a sealant to the edges (mastic, caulk or adhesive tape), then cover the whole area of the tear with a scrap piece of belly wrap that is also mechanically secured and sealed.
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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED HOMES:
Illlustration above - from Moisture Problems in Mobile Homes, by the Manufactured Housing Research Alliance
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