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Understanding the Differences Between "Manufactured" and "Modular" Homes

Mar. 9, 2009

One of my pet peeves is when I hear someone refer to a manufactured home - one that has a steel chassis and a wheeled truck and was literally towed to the home site - as a modular home. Inspectors, please, STOP referring to manufactured homes as modular homes!

Home inspectors need to use the correct terminology when describing things to their clients - especially when it comes to a type of structure. Imagine what would happen if an inspector, that doesn't know the difference between a modular home and a manufactured home, were to continually refer to a modular home during an inspection as a "manufactured home." In the minds of many, the term "manufactured home" cues up mental images of double-wide trailers; that inspector might actually cause the potential buyer to run away from a home that's built better and stronger than a stick-built home as most modulars are.

Conversely, calling a manufactured home a modular home during an inspection only perpetuates the idea in the mind of listeners - particularly real estate folks - that a manufactured home and a modular home are the same thing. Agents are liable to continue to go around mistakenly calling manufactured homes modular homes after that, because they heard the inspector - who's supposed to be an expert - call a manufactured home a modular home.

As a profession, we really need to ensure that we are clear about the differences and that we don't confuse them in the minds of buyers. A manufactured home has a full-length steel chassis beneath it and its own wheel systems (trucks) as well as it's own draw tongues. It's towed to the home site on its own wheels in sections, just like a pair of trailers, it's set on the supporting foundation - whether it's just block piers or something more elaborate - and then the trucks and tongues are removed.

A modular on the other hand is built in a factory in the form of heavily reinforced boxes known as "modules" and then those modules are individually trucked to the site on flatbed trucks, lifted into place on a permanent foundation by a crane, and then the home is completed.

Are there similarities between the two? Sure, both are built in a factory setting, both have restriction on section size that's dictated by what can be legally carried over the highway system, both are pre-wired and pre-plumbed and might be complete when they leave the factory, but that's where the similarity ends. Manufactured homes are intentionally built lighter to a manufactured building code, not conventional building codes, so that they'll be lighter and easier to tow over the highway. Don't confuse the two and don't perpetuate the myth that a modular home is akin to a manufactured home and is therefore inferior to a stick-built home when the opposite is more often the case.

You might be reading this and thinking to yourself, "Ah, O'Handley is off his nut, nothing bad can happen if I have a slip of the tongue and call a manufactured home a modular home." If you believe that, I've got the deed to the Brooklyn Bridge and will be happy to sell it to you.

Just imagine for a minute a buyer who has heard that a modular home is built stronger and better than a regular stick built home, but knows little more than that. The buyer goes to his/her realtor and says, "I want to buy a modular home because I've heard they're pretty good." If the realtor thinks that manufactured and modular homes are the same thing, the realtor is liable to try and dissuade the buyer and might say something like, "Oh no, modular homes are not as well built; you're misinformed. You really don't want to buy one of those."

Worse, what if the realtor thinks manufactured and modular homes are the same thing and hasn't the least idea how a true modular is built? The realtor might take the buyer around to look at nothing but manufactured homes; and, if those manufactured homes are like some around here, there's liable to be very little outward indication that the home is actually a manufactured home. The buyer, not really knowing the difference, might make an offer on a manufactured home under the misbegotten belief that it is a modular home.

This kind of identify mix-up is not as far-fetched as if sounds; I know that because I personally was involved in such a mix-up. I did a home years ago that from all outward appearances appeared to be a stick-built rambler with a two-story addition. As I commenced the inspection and did the exterior, nothing seemed out of the ordinary; however, when I got onto the roof of the one-story rambler half of the house I could clearly see a slight change in the roof plane near the eaves that looked like the roof overhangs had been extended. This looked like either eaves had been added to a home without the deep overhangs that are typical here in the northwest or repairs had been made where the rafter tails had been rotted out. It was hard to tell because the eaves were completely enclosed behind sheathing. 

However, inside the home I began to notice things in the one-story part that told me that it was probably a manufactured home that had been placed on a permanent foundation and had the eaves extended to look like a normal ranch; things like thin drywall, a thicker than normal center (marriage) wall that ran end-to-end, polybutylene plumbing and smaller-than-normal bathroom fixtures molded from fiberglass.

I mentioned my suspicions to the client, at which point the agent interrupted me and insisted that it was not a manufactured home but a modular home. She explained that the owner had advertised it as a modular with a stick-built addition, and she opined that I must not know the difference. I pointed out to her that I had grown up building houses and that my own father built modular homes the last ten years before he'd retired, so I definitely knew the difference. Nonetheless, she insisted that I was wrong and she clearly was slightly angry with me for suggesting that the home was most likely nothing more than an altered double-wide.

Since it was obvious to me that the realtor actually believed what she was saying, I decided to deviate from my normal inspection routine and inspect the crawlspace before I inspected the interior or the electro-mechanicals. I figured that there was no point in going on with the rest of the inspection if the client really wanted a modular or stick built home and didn't want to purchase a manufactured home. As soon as I crawled under the home I found the trucks, the steel chassis and both draw tongues beneath the one-story part of the structure. When I came out of the crawlspace and told the client, who'd flown in from the mid-west to see the home had made an offer and then flown back home, only to return for the inspection, that it really was a manufactured home, the client went ballistic. He verbally lit into the real estate agent like Mike Tyson into a speed bag. I started packing my gear - it was obvious that the client didn't want me to go any further. What was sad was that the agent looked genuinely surprised; I really think she'd been deceived by the seller.

Sure, I did my job and got paid, but the whole unpleasant mess could probably have been avoided if the homeowner hadn't called the manufactured home portion of the building a "modular" home, thus giving the agent the wrong information, or if the agent had know enough about the differences between the two to detect a manufactured home.

So, what if I hadn't known the difference between a modular home and a manufactured home and had told the client that I thought that the one-story portion of the home was a modular home? The agent would have stepped in to confirm that, based on what she'd been told, and I would have come out of that crawlspace and said, "Yep, it's a modular just like she said?" The client might have bought that home. Can you imagine the fix I would have been in if later if the client, now the homeowner, discovered that the home wasn't a modular at all, and that he'd spent easily twice what the home was actually worth because I'd used the wrong terminology? I probably would have been sued out of business by now.

Here are some important things to remember:

  • Modular homes are built to the existing model building codes. They have full-depth walls and kitchen and bathroom fixtures are full-size types like you'd see in any regular home.
  • Look underneath - modular homes have a wood frame beneath and are placed on full perimeter foundations; they don't have a steel backbone chassis or any leaf springs, trucks, or draw tongues and lights beneath them. When you look at the underside of a manufactured home you'll see a large steel backbone chassis that's painted back and you won't be able to see the framing on the underside of the house because it will be concealed behind a woven black nylon dust cover.
  • Both modular homes and manufactured homes have a marriage wall but the marriage wall in a modular is typically at least 9 inches thick whereas the marriage wall in a manufactured home is often about 6 inches thick.
  • Modular homes usually have conventionally sized hinged roof trusses with access into the roof plane; manufactured homes typically have very light weight roof trusses without any access into the roof plane.
  • The exterior shell wall of manufactured homes is often (not always) thinner and framed with 2 by 3 lumber while the exterior walls of modular homes are conventionally framed.
  • The interior wall and ceiling surfaces of modular homes are covered with 1/2-inch gypsum board but the interior walls and ceilings of manufactured homes are typically covered with a lot of thin wood-grained or vinyl-covered paneling or 1/4-inch gypsum board. 
  • Talk to the neighbors and ask whether the house was rolled in on it's own wheels or arrived as a bunch of large boxes that were sling-loaded off the truck onto the foundation with a crane.
  • Look for the manufacturing plate - it's usually in a cabinet in the pantry or sometimes it's nailed to the side of one of the boxes. Google the manufacturer's name to confirm whether they build manufactured or modular homes.

So, the bottom line here and the message that I'm trying to convey with this long ramble is THINK before you open your mouth to describe something or put a pen to paper to report something; and fer cryin' out loud, use the correct terminology.


Mike O'Handley, Editor - The Inspector's Journal (TIJ) - - Your Inspector Inc., Kenmore, WA 425-298-8413

User Comments

1. RE: Understanding the Differences Between "Manufactured" and "Modular" Homes

Written by: Jason Jelonek
Jul. 24, 2015

Thanks for helping distinguish between manufactured and modular homes.   

The manfactured homes are similar to what was once called mobile homes.

Alas, here's a link to a page showing more about modular homes with very popular videos show an actual modular home build.  It's a bit rough, but you'll get the gist of how modulars are different. 

Thanks again,


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frag der Hausdok (Ask the House Doctor)

Kenmore, Washington

Got questions about a home's structure or systems in a home or about home inspections? This is the place to ask them. I grew up in construction and then spent most of my military career as an investigator. When I retired 13 years ago, I combined what I know - house and investigations - to become a professional home inspector. Since then, I've established a webzine that's sort of like RealTown for home inspectors - The Inspector's Journal (TIJ) and I'm the Journal of LIght Construction Online's building science subject matter expert. I'm your go-to guy for information about the home inspection profession; ask me whatever you want about the home inspection profession. You'll get the unvarnished truth and when I don't know the answer I'll get it for you.


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RE: Understanding the Differences Between "Manufactured" and "Modular" Homes
Thanks for helping distinguish between manufacture...