Modular home four sections (C) Daniel FriedmanMold Contamination in New Modular Homes
Case report: finding hidden mold in modular construction

  • MODULAR HOME MOLD CONTAMINATION - CONTENTS: how to suspect and then find hidden mold in building walls, ceilings, floors, under carpets; special hidden mold risks in improperly-transported modular home sections. Mold related illness traced to hidden mold that contaminated clothing.
  • POST a QUESTION or READ FAQs about hidden mold contamination in modular-constructed buildings

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Mold contamination in modular constructed homes:

This article describes instances of problematic or harmful mold contamination found hidden in walls, flooring, and even cabinets of a modular home that traveled in rain without adequate seal-protection against water entry. Other cases of mold concerns or mold contamination in modular homes are included.

A look at why we suspected that there was hidden mold contamination in the home and how the extent of mold contamination was determined can assist in investigating any building for hidden mold problems.

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Mold in Modular Homes

Mold may be found in surprising locations in modular homes depending on the home's delivery conditions and construction history.

Leaks & mold growth in wall cavity, modular home exposed to rain during delivery (C) D Friedman Photo of mold on modular home wall cavity surfaces (C) Daniel Friedman

Residential modular home structures include cavities between floors and some walls that an inexperienced inspector may fail to consider. Knowing that water had entered this modular structure we obtained permission for some destructive inspecting that helped track how water had moved through the building.

Field Report of Extensive Hidden Mold in a Modular Home: Mrs . X (Sick of mold)

Modular home main girder (C) Daniel FriedmanMrs. X (Sick of mold) , living for a year in a modular home constructed new for herself and her husband in Newburgh, New York, developed severe mold-related illness. Ultimately she had to travel in her pajamas and by ambulance to a local hospital where she was admitted and treated for more than a month.

Feeling better and about to be discharged, Mrs. X (Sick of mold) asked Mr. X (Worried) to bring her a clean outfit from home so that she could return home in something nicer than her pajamas X (Worried) stopped by their home that to him looked and smelled clean, if a bit lonely. He selected a full outfit from a closet used by Mrs. X (Sick of mold) .

When in the hospital Mrs. X (Sick of mold) opened the suitcase of clean clothes she went immediately into anaphylactic shock, scaring everyone, especially Mr. X (Worried) and extending her hospital stay by another week.

A suspicion reared its moldy head: maybe there was something moldy about the clothing that mold-sensitive Mrs. X (Sick of mold) had taken out of the suitcase. The owners asked me [DF] to investigate.

I [DF] was engaged to inspect the home and was given permission to perform invasive inspection as needed to find possible mold contamination in the building.

Modular home four sections (C) Daniel FriedmanThe house looked new and clean. But in the basement it was curious to see mud splashed up against the under-side of the home. Curious but not unusual. But then I saw what looked like water marks on the mating beams and at the sill plates.

Notice that there is no housewrap and no siding on the gable ends of the four sections making up this modular home.

[Click to enlarge any image]

Moving back upstairs I lifted back the wall to wall carpets at their corners. Water stains and a bit of mold were plain to see.

Based on what I saw there, made some test cuts along the bottom of walls around all sides of the main floor of the home.

In wall cavities at all of the exterior walls near floor level and even in the marriage wall cavities I found very extensive mold contamination.

I also found extensive mold contamination in the building's fiberglass insulation in all of its exterior walls. Attic insulation was mold-free and did not appear to have ever been wet.

On reviewing the construction history I learned that the home had been delivered and set in rainy weather. The owners also told me that they had observed wet carpets and water in kitchen cabinets at the time the home was delivered and set but as no one saw any mold no one thought further about that wetting event.

Modular home during highway transport (C) Daniel Friedman The modular home section shown at left was being transported with adequate weather protection.

But a review of the owner's photographs of the modular home sections arriving at the site we could see that the front ends of the modular home segments had been shipped from the factory without the usual careful plastic wrap to protect the un-finished side of the home from the weather.

Driving a modular home up New York's I84 in rain at 65 mph or more forced water into the building's wall and floor cavities and into portions of the interior, as well as forcing water into the party or marry walls of the structure from whence it had entered kitchen cabinets.

The home would have required a gut-renovation to remove all of the moldy drywall and insulation. The manufacturer elected to replace the unit with a clean, dry one.

Reader Question: mold in 2005 modular home

(Sept 12, 2014) Dan said:

We bought a used 1995 modular home in 2005 that consists of one middle pod (10 ft ceilings) and two side pods (8 foot ceilings). The roof line is 4/12 pitch. When you enter the attic space up to the middle pod (which is overlaid with metal sheeting) you can see all the way to the other end.

However, in order to get from the middle pod to the side pods, you have to crawl through a small opening that was cut out by one of the workers. Everywhere else there is a wall of plywood that separates the lower section (side pods) from the upper (middle pod). I did not think much of it until we found out that the lower sections now have mold growing on the underside of the plywood for the roof.

A mold inspector told us that this plywood was preventing air from circulating. In short, he said that the eave vents have no way of circulating air with the middle pod's roof vents. My question: What is the purpose of the plywood? Should it have been removed?

During this discovery, we found out that a sewer vent, and two other air vents were never vented out through the roof. In other words, the vents were exhausting warm air into the attic. The mold inspector commented that the combination of these two failures brought on the mold which is now making my family sick. 2nd question: What can I do about this huge problem we now face?

This question appeared originally at MODULAR HOME CONSTRUCTION



What a mess. Under a 4/12 roof the accessible area under the lower slopes is very limited - too limited to think about adequate cleaning & insulation replacement from inside the attic space.

That leaves two approaches: tear off all of the roof, remove all insulation, clean and seal all surfaces, re-insulate, re-roof,
Tear down ceilings indoors and do the same job from inside.

The second approach is more disruptive to the occupied interior and increases the risk of cross contamination and thus the need for still more indoor HEPA vacuum cleaning and wiping.

Normally I oppose heroic, expensive roof tear offs to address attic mold as not being justified. But I would not want to leave a large problematic mold reservoir in a building: indeed air movement can move "backwards" down into a structure in some conditions.

I would first do some careful sampling of the molds present: on plywood, in insulation (by vacuum testing) and on the attic side of ceiling drywall. If none of the molds found are highly mobile - highly harmful (e.g. if it's just some simple Cladosporium) I might do nothing except fix the venting. Otherwise, I'd consider the remediation I outlined above.

The plywood was doubtless in place to enclose and protect the structure during transport.

Leaving it in place indeed blocks the proper roof ventilation.

Failure to vent plumbing vents to outdoors is a site set-crew SNAFU which is another example of why modular companies often want their own crews to set the house. Modulars encourage construction by builders who don't know enough about building.

Tell me the state where you are located and the brand and model of your home and I can research this further.

Kudos to your home inspector.

Also see MOLD GROWTH on SURFACES, TABLE OF our table of mold growth locations in buildings where we include other comments on MOBILE & MODULAR HOME MOLD


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