How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

What are the most common problems with older mobile homes?

Saturday, October 6, 2018

Here’s our “Top Ten” list of recurring defects we find in older mobile homes. It may seem more like a rant than a list, but most of these problems are avoidable—and we see them again and again. 

1) Damaged “belly wrap.” The underside of a mobile home is covered with a plastic sheet, called a belly wrap or bottom board in the industry. 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 gets 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.

   Better-constructed 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.

2) Leaking skylights. Better quality skylights have a raised curb around the perimeter and are carefully sealed by down-lapping between roof material and caulked. The type shown below, with virtually no curb, always leak after a few years. 

3) Homeowner-installed wiring. A mobile home leaves the factory with an electric distribution panel already installed and wired to HUD-safety standards. We never find anything wrong with the factory-installed panel, unless the homeowner or a handyman has added circuits to it. The main service panel, typically located on a power pole near the home, is another matter. Amateur electrical work, with unsecured and unprotected cables, open holes in the panel box, and wiring not matched to the rating of the breaker it’s attached to, are all typical defects. 

4) Polybutylene piping, also called “PB” in the trades, was used in residential water supply piping from the early 1980s to 1995. It was billed as “the pipe of the future” at first, and its low cost and easy installation made it an alternative to traditional copper water piping. PB was especially prevalent in mobile homes.

    The pipe is typically gray, with copper-color band connections. While gray is the most common color, polybutylene can also be blue or black in color. It is usually stamped with the marking “PB2110.”

    Throughout the 1980s lawsuits, claiming that defective manufacturing and installation had caused hundreds of millions of dollars of water damage from ruptured pipes, began to mount into the thousands. Although the manufacturers never acknowledged that PB pipe is defective, they eventually agreed to fund a class action settlement for just under a billion dollars to resolve homeowner claims. The period for filing a claim ended in 2007.

    Replacement of the water supply piping costs several thousand dollars. Because of the public awareness of the risks involved with PB piping, its presence may reduce a home’s value in the marketplace. It can also cause higher homeowner insurance premiums or denial of coverage.

5) Washing machine drains onto ground and dryer vents into crawl space. Rerouting the washing machine drain onto the ground is considered a home improvement by some people, based on the false premise that draining wash water into the septic tank overloads the system. Actually, as your local health department will verify, this modification puts human fecal matter and bacteria on the ground due to the inevitable occasional “skid marks” in underwear. It is considered a health hazard.

   Dryer vents are extended to a exterior termination with a flap closure when the home in installed, but an elbow connection can come loose under the home. Then again, sometimes the homeowner relocates the dryer and doesn’t run a new vent out to the exterior. Many manufacturers include a warning label on the laundry room wall, like the one below, about the dangers of terminating the dryer duct under the home.

6) Premature roof deterioration. An asphalt shingle roof over an unvented or poorly vented attic space in a mobile home will age faster than normal due to heat buildup in the attic. The shingles crack and begin to curl at the edges before their time. 

7) Pier settlement and loose tie-downs. Most mobile homes in this area have a foundation that is stacked concrete blocks on a plastic pad. Because the pads are not anchored into the ground below or the steel frame of the home above, any soil movement under them causes the piers to lean and lose contact with the steel frame of the home. Settlement can also cause tie-down straps to loosen. This is one reason why it is especially important to prepare the site so that it slopes away from all sided of the home when installed, or that a small berm be constructed that redirects rainwater flowing downhill so that it runs around the area under the home.

8) Water leaks around exterior doors and windows. Poorly flashed window openings with little or no caulk start leaking at the first rain after installation of the home, but the evidence sometimes takes several years to show up as staining on the interior walls. We use an infrared camera to locate these leaks early.

9) Homeowner-built additions. While site-built additions to a mobile home are acceptable, HUD is specific about one thing: the walls and foundation of the home are only designed to carry their own weight. So any additions, including roofed porches, should not bear on the walls or roof of the home. Tie-down anchors that are damaged or removed as part of a home addition as also a no-no.

10) Damaged or missing skirting. It’s only effective if the skirting completely encloses the home without any openings. While string-line grass trimmers do cosmetic damage around the base of the skirting, it’s a couple of sections of missing panels that open up the underside of the home to multiple other problems. Financial institutions require a mobile home to be fully skirted in order to mortgage the property, because they know skirting is second only to the roof as a way to protect their loan collateral from damage.

    Also, see our blog post Does it make sense to buy an older mobile home and remodel it? 


• • • • • • • • • • • • • • • • • • • • • •

Want to learn more about inspecting
manufactured/mobile homes? 
Get our  Handbook for 
Manufactured Home Inspectors 
at for $19.95

• • • • • • • • • • • • • • • • • • • • • •

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? 

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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