When Mold And Mildew Attack The Tiny

I’d not given much thought to mold and/or mildew when we first began our tiny house adventure. Truth is I am not sure I even knew the difference between the two. But I know I had certainly not thought about how mold and mildew could attack our tiny house. I did realize the obvious. Leave standing water on a surface long enough and mold spores would take root. Leave food out or hidden in the house and mold would eventually begat freebase penicillin. But what can you do to prevent mold and mildew and what do you do if it has taken root?

My first mold realization came in late 2011 when Logan Smith wrote the following on Mobile Cabin Works:

Much to my surprise, if you lay a futon mattress directly on top of a loft floor it will breed mold. Who’d a thunk it? The science behind this is obvious once you realize what’s going on. The heat generated by your body and the coolness of the floor, especially a non-insulated interior ceiling/loft floor, combine to produce condensation. This moisture is then held in the fabric of the mattress as it has no way to be evaporated due to the lack of ventilation. So I will provide you with this scientific formula. The NW + moisture = green stuff. If you live here, you understand.

Now I don’t live in the Pacific NW so I never thought much about mold in so much as it wasn’t something we had had before or that I had seen in my folks house. Yes, there was the mold that grew around the tub if you didn’t clean regularly. There was mold on bread that had been sitting in the roll top too long. But mold running up a wall or appearing on sheetrock or even over head, just never worked out for me. I realize now though it is possible and is something that needs consideration.

Mold – a large and taxonomically diverse number of fungal species where the growth of hyphae results in discoloration and a fuzzy appearance, especially on food.

Mildew – a thin, superficial, usually whitish growth consisting of minute hyphae (fungal filaments) produced especially on living plants or organic matter such as wood, paper or leather.

What’s wrong with a little mold or mildew though? So long as the pores remain out of sight and stay put behind the laundry tub, under the basement carpet, or only peek around the edge of the bathroom wallpaper, who cares? We all should actually because they are eating us of house and home and are effecting our health, too.


    • When washing machines in a room without a floor drain overflow or hose connections burst, water with no point of exit will soak into adjacent carpet, drywall and insulation. SOLUTION: Provide a floor drain near the washing machine. Install an overflow pan directly under the machine or install a lip at the doorway to contain overflows.
    • Water-resistant drywall used as a tile backer quickly degrades once subjected to moisture. SOLUTION:
      Install cement backer board, which will remain structurally sound even if repeatedly subjected to moisture.
    • Poorly ventilated bathrooms row. SOLUTION: Install a bathroom fan (or at least, open a window) to exhaust moisture. Remove surface mildew by scrubbing the area with a 1/2 percent bleach solution. When the area is dry, prime it with an alcohol-based, white pigmented shellac, such as Zinsser Bullseye, and use a paint containing mildewcide.
    • Humidifiers (especially reservoir-type central units and portable units) provide both a growth medium and a distribution system for mold and mildew. SOLUTION: Clean and treat the reservoir often with an antimicrobial solution which can be bought at most convenient store.
    • Improperly flashed or caulked windows (and those with large amounts of surface condensation) let moisture seep into the surrounding wood, drywall and insulation. SOLUTION: Properly flash and caulk windows during installation; minimize condensation with good ventilation and airflow.

Ceiling Mold


Remember. Some types of molds are toxic so do not attempt to use this post as an EPA-certified guide. Remove and treat mold at your own risk!

You can easily remove minor mold with ordinary household cleaning products. I prefer Mold Armor. Mold and mildew can also cause breathing disturbance if you suffer from allergies or have a weakened immune system so it is important to isolate the spores and remove them as quickly as possible. To do so, you can also create your own anti-mold mix by mixing 1/2 cup bleach, 1 qt. water and a little detergent. The bleach in the cleaning mixture kills the mold, and the detergent helps lift it off the surface so you can rinse it away. You may also want to protect yourself from contact with mold and the bleach solution by wearing a long-sleeve shirt and long pants as well as plastic or rubber gloves and goggles. If the mold doesn’t disappear after a light yet abrasive scrubbing, reapply the cleaning mix and let it sit for a minute or two. Then lightly scrub again. I use either an old toothbrush or a small, palm-sized dish scrubber.Once the mold and mildew spot is treated you will want to change conditions so it is not as easy to set in again. This way you can be sure your tiny house is as healthy as possible.

NOTE: Top hiding spots courtesy of: The Family Handyman 

16 thoughts on “When Mold And Mildew Attack The Tiny”

  1. One solution I thought of a while ago is to built a tiny home as two sections: a living space and a “wet” space (kitchen and bath). A short (removable) connection could be built between them.

    The sections could be made from different materials, the living space from wood, and water-resistant materials (e.g. metal, ceramic, plastic) for the other. Towing two sections in series is more difficult (and heavier) than towing one, but still feasible. The living space could be towed alone for travelling, and the wet space alone easier cleaning.

    As for mattresses, some youth hostels I have stayed in use vinyl covered foam which is impervious to sweat, bedbugs and other problems. A watertight or easily washable mattress system might be the answer.

    • Having a waterproof cover didn’t help my trailer foam mattress. It just made it take longer to dry out the condensation that formed. Good airflow is key.

  2. To stop mold under your mattress in the loft, I’m assuming it is it to surface structure, cut breathing holes under the mattress and inconspicuously on the other section at the bottom as well. We had the same problem in a built-in bed in our guestroom we cut strips with holes on each and going down the links of the boards it did not compromise the strength of the structure when little bit and mold problem in the mattress was solved . It just needs to breathe and have airflow

  3. Is it all about condensation between the walls if you are getting mold between the sheet-rock and the outside wall? When the tiny house is built are weep spots in the allowance? What if anything is done in the tiny house to ventilate?

  4. I had a huge problem with moisture and mold on the bottom of a foam mattress laid directly on the fully enclosed fibreglass built-in bed in my Boler trailer. There was also a moisture problem inside the space resulting in mouldy shoes and other items stored below the bed. I replaced that setup with an open fronted wood frame with slatted bed base and haven’t had a problem since. I also use calcium chloride crystals to absorb moisture in the closet (modified to a pantry) which helped a lot there. Next I’ll be replacing the enclosed fibreglass dinette seat to ensure better air flow.

  5. When I was a child on my grandparent’s farm, I can remember my grandmother taking the mattresses out to air at least once a week. She’d line them up on the south-facing veranda to let the sun hit them, turning them once to treat the other side. Hospitals used to do this with mattresses as well, a very long time ago. Sunlight can kill a great many things, and the air circulating around the mattresses helps prevent the growth of mold and mildew. It also allows the area where the mattress is located to have a bit of breathing space. This is more difficult to achieve in the winter, and I’m sure some neighbour would complain that a town by-law was being violated. Still, it has taken only one or two generations for people to utterly forget the cleaning habits of old and why they were done. Unless we can all afford maid service to do it for us, it would be in our best interests to relearn those old cleaning techniques.

  6. I guess they are not familiar with futon care, you have to air them out and beat them in the sunshine. Airing and sun helps kill the mold and bacteria & beating it (much like you would a rug) gets some of the debris from your skin off (and out) of it. . . Futons are much easier to keep mold out of then traditional matresses you just have to know how to care for them. The reason for that is Japan is a humid place & mold / mildew are issues. If you want to know how to manage mold/mildew I suggest looking at Japanese blogs. . . They also have these products that absorb moisture around the house. Heck, they even have special hangers with a hollow space to put moisture absorbers (reminds me of a blogger that started living in japan and opened his closet to all his stuff being covered in green slime & ruined).

  7. You should never use bleach to treat mold. It loves that stuff. The best product I have used is at the Dollar Tree. It is one dollar and is called Mold and Mildew remover.
    If your clothes have a mildest smell, as the commenter stated about mattresses, place those clothes in the sunlight for a few hours. The odor will be gone.
    Living in the very humid South, the problem of mold and mildew is common. Try a dehumidifier. Also, propane heat dumps up to a quart of moisture into the air per hour. Try electric heat or a tiny ceramic wood stove.
    My Pinterest site has a lot of good guides for off grid and Tiny Home living.
    Kill is a great primer to paint over mold. It won’t reappear in that area.
    One of the best remedies for mold is just plain fresh air flow and sunlight. Install an opening skylight on your lift ceiling. It can also serve as an escape hatch.

  8. In my closet I hang a couple of bags of damp-rid (Home Depot or Amazon). There are crystals on the top and as they collect moisture that drops to the bottom bag. When the crystals are gone, toss them and hang new ones. Damp-rid also comes in tub forms.

    I also have a small heating unit that sits on the floor, plugged in, which gives enough heat to collect moisture. I can’t remember what it is called but it does a good job in my small bathroom.

  9. This is the first year I have experienced mildew in my tiny house. I have paint grade pine walls, and where ever there is a dresser or a shelf, from a foot up from the floor there is mold or mildew on the wall. I do not have electricity and can’t run a fan. Will just opening a window help this? I wonder if my windows were all open more last year. I have a high window that I usually leave open but it has been colder this year in Oregon. Also, I’ve been told a solar fan could help, but they only run when the sun is shining on them. So that’s in the daytime when it’s sunnier and warmer. Do you think that would help? Thank you


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