Buying A Mold Free House

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Photo of a downspout set up that will cause water damage.

This photo depicts a simple mistake that can ruin the foundation of a house. Downspouts draining near the house, or any other source of water near the foundation can create a moldy situation under the house or in the walls.

Examine all aspects of a perspective new house for any possible signs of current mold, water damage, or set-ups that might instigate water-damage such as this downspout that was not built correctly.

Is There Such A Thing As A Mold Free House

Trying to find a house that is mold free is difficult. Not only are some materials moldy prior to installation, contractors may use building techniques that are more prone to mold growth. I all too often see contractors building in the rain without protecting the house or apartments they are building. These buildings can be sitting in the rain for days on end with the cellulose materials just soaking up the water.

The fact that buildings are also built with  materials that tend to grab moisture from the surrounding area and hold onto it does not help. This means a building built in a high humidity environment may be moist also. Even when the building has been kept dry during the construction process, high humidity in the environment from daily living can be enough to cause damage to some building materials. Then there are tiny pipe leaks that moisten the cavities of walls, roof leaks, window leaks - the list is endless. It is a miracle there are any homes that are not water-damaged.

The current thought among building biologists is that a building should be built to convert moisture into vapor. Cultures around the world have been using building biology and building materials to convert water moisture into vapor and wick it away as long as we have had buildings. There is a building revival  to use these types of building materials and practices in the U.S.A. now, and a move away from non-breathable materials. However, you and I are at the front of this wave, so it will be years before this becomes common practice.

The sad truth is that there is no practical way to eliminate all mold, mold spores and mycotoxins in the indoor environment. We eliminate them as much as possible through proper building materials and methods and in addition, we control indoor mold growth by controlling moisture. However, since our body as well as our activities create moisture, it is important to create buildings that can allow this moisture to be removed by passive or active methods to the outside. (Sometimes this is as simple as opening a window on a dry day.)

So, to answer the question, a totally mold free, spore free, mycotoxin free building does not exist, BUT we want to find a building that will at least not cause us to react to the building. That means one that is not water-damaged and that hopefully is built to convert moisture into vapor (hard to find), and in a manner that will decrease the change for future water damage.

That is about as mold free as we can ask for.

Identifying A Mold Free Home

Your nose is the most helpful tool you have in identifying a mold free home. However, I realize not everyone can sniff one out and you may need other things to indicate that a home may already be moldy or may get moldy easier in the future. Additionally, there may be more smell at certain times of the year or the house may have been partially remediated making it smell and look better for the moment.

I think the easiest and quickest way to tell you what to watch out for in a potentially "moldy" house and what you want to find in a potentially "non-moldy" house is to make you lists. I have a very long list of things you do and don't want in a house, and I realize it is hard to find this perfect house, but it gives you a good idea of what to look for and potential hazards that might induce mold growth. Even if you purchase a house with issues that may lead to later mold if you have water damage, you know this could be an issue down the road and to watch it closely for moisture intrusion. If you do get moisture intrusion, check out "My House Has Water Damage". If you actually have a mold issue, check out "Finding Mold In Your Home" and "Cleaning A Moldy Home" and "Cleaning Mold off Your Stuff".

I have undoubtedly left things out below, but have tried to think of as many things as I can. Hopefully, it will guide you to a safer house than you might have found otherwise.


What You Don't Want In A House

  • Built on a flood plain
  • Built on wetlands
  • Built with springs under it or right next to it
  • A house that is lower than the land around it
  • A house with a basement
  • If house that has one or more of the above attributes but has poor or inadequate drainage around it, it becomes a much worse situation.
  • Lacks or has improper flashing on the roof, walls, door and window openings
  • Mold growing on the poorly painted house
  • Noticeable mold inside the house
  • Musty smell to house - Be suspect if the house has any type of air fresheners in it. They are usually used to hide other smells.
  • Water stains on building materials or other signs of water damage
  • Neighbors with a moldy house or using lots of chemicals
  • Wet or bad smelling crawl space
  • Any leaks anywhere
  • Musty smells under sinks, sniff all of them
  • Shower drain that is not intact or leaking
  • HVAC system that smells bad when it is turned on, or it is not properly sealed, or has growth on or in it.
  • Roof covered by moss - might be okay, but look closely
  • Showers or tubs that have failed caulking or failed grout.
  • Failed caulking anywhere on the outside walls of the house
  • Improper or failed gutters/drains spout may cause water damage to house - check if you see this
  • Things can get into HVAC vents such as mice that die, someones food etc. They then may grow mold on them and smell spreads through house - Check - Not a good sign if there is mouse smell, as their dander is highly allergenic for many people.
  • A house built on a slab - might be ok if built with methods that allow it to breath and magnesium oxide cement rather than calcium (Portland cement) I personally don't trust houses built on slabs as a general rule.
  • House with musty attic or attic ceiling sheathing/walls showing water stains or mold growth
  • If the house has some type of strandboard material on the outside, it better have a great caulking and paint job or that is an issue. I don't like this type of siding as it is very prone to damage and mold, but you see it on many houses.
  • HVAC ducts in attic or crawl space without insulation on the outside of the ducts
  • HVAC ducts are better off in main part of house, or next in attic, but if in attic, or even crawl space they better be completely closed off and well insulated.
  • HVAC ducts are not metal
  • The irrigation is hitting the house or pooling beside the foundation.

What To Look For

  • A roof that hangs way out over the house and protects the walls and window openings from rain
  • A house that has land sloping away from it.
  • Good drainage around the house
  • Good flashing on the roof, walls, windows and door openings.
  • An unprotected outside door facing to the West. Needs a storm door on it or a roof over it.
  • Well protected by some sort of paint or other protective coating
  • Proper venting in the bathroom, laundry room, kitchen and any other room that might produce extra moisture.
  • The crawl space is enclosed properly and has no bad odors
  • Clean looking and good smelling HVAC
  • No sign of water damage such as stains on walls, flooring, ceilings
  • House inner walls  built with covering of magnesium oxide board is best, or wood, but next is plywood and last is sheet rock/gypsum/drywall
  • House sheathing is magnesium oxide or wood or plywood (least on list, but better than strand board)
  • A roof that is really well built to protect the entire house. Has proper flashing if needed (most roofs need it).
  • Vents around the foundation
  • Vents under the roof overhang that go into the attic
  • An attic - houses with no attic stops you from getting up there to see roof damage until it is coming through your ceiling. If there is an HVAC system enclosed in this space, you can't get to it either.
  • HVAC looks clean, ducts are metal and insulated if in attic or in crawl space.
  • The house has no odd or bad smells.
  • The doorways have a roof going out over them.



The Terrain We Build Upon

It is really important for the ground under the house to be dry. This means the house needs to be above the ground around it or at minimum not have any ground around it sloping towards the house. You don't want any source of underground water such as a spring or high water table to end up releasing moisture into your crawl space.


The Constuction Practices

Trying to buy or build a home with materials and construction techniques that will be less likely to grow mold is also not an easy task. Remember, the current thought among building biologists is that a building should be built to convert moisture into vapor and move it out of the building.

In yesteryear we built buildings with regional building practices that were based on the needs of the local climate and environment. Building practices have become standardized from one locale to another and no longer tend to take regional needs into account.

Additionally buildings have become tighter and lack ventilation. This leads to increased moisture in the home unless methods are used to release this moisture from daily living to the outside.


The Building Materials

Keep in mind that we want mold resistant materials that wick moisture to the outside and don't bring it inside.

There is a sad and contentious discussion among the building biologists and those who want to hold onto the old way of construction in the U.S.A. Changing over to less moisture prone building materials that are  safer, and healthier are a huge social cost. To admit that many government and private buildings are made with mold prone materials and mold prone building practices and that these buildings are making people sick opens a big can of financial worms that almost everyone would be affected by in one manner or another. This would induce massive amounts of law suits and over night people would become dissatisfied with the current housing and work environments. This is why what will probably happen is a slow change in construction practices and if you want a healthy home, you have to educate yourself, find an educated builder or if able, build your own.

I would suggest if you want to look into other choices of building to find a building biologist in your area.  Check out this website that is owned by a building biologist. I will admit he is not updating his site well, and he does have some types of buildings listed that I would not use as I find they have mold issues, such as straw bale homes. Although, if the straw bale home is protected well, it may be fine, but any leaks and the mold in the straw will grow like crazy. I have heard him speak and he does seem to have a good grasp on the needs of mold sensitive indivudals and he would be a good person to consult with for non-toxic, breathable construction. He also has many websites for alternative construction materials such as magnesium oxide materials on his web page.

I have a friend working on a website that will have data on building materials that are safer for mold illness prone people to live in. I will post it here when she is done with it. In the mean time, I have listed a few thoughts below.

Sticks And Paper Currently Used

Wood is often used in building but you have to assume it is contaminated from the get-go. Often it already has mold on it, even if you do not see signs of it. Some builders suggest to use a mold-resistant mineral coating on wood used in buildings. A friend of mine suggests Lime paint (whitewash) and borax as two options. Also stay away from or limit the following mold-growing materials - paper backings, resin-containing boards (like particle board, melamine, etc.), fiberglass, foams - including "eco-foam".


External Sheathing and Internal Wall/Ceiling Covering

Magnesium Oxide boards seem like the best option around as far as something that converts moisture to vapor, is more moisture proof and is still fire proof. There are forms of it to be used as outer sheeting on a building as well as inner walls. Magnesium oxide can be built into concrete forms also to be used as foundation. It has many uses. Some people are mixing it with clay and spraying it onto wood or all over water-damaged cavities after remediation to contain them. Many, many uses for this product.

Here are a few magnesium oxide board and loose magnesium oxide product websites

Magnesium oxide board products:

Magnesium oxide,

Magnesium oxide, orthophosphates and silicates:


Standard fiber glass dehydrates slowly and has fire retardants added as well as biocides. The pink insulation is banned in the U.S now but the new ones are still highly flammable so they still have fire retardants and biocides as they hold moisture still. The newest ones have plant based binders rather than formaldehyde at least.

What some people are using as insulation is rockwool and it is being sold under a variety of names at your local hardware store.



The old Portland style concrete is not really as old as we think. The calcium used in it is a new way of making concrete. In reality, the magnesium oxide use to be used in concrete and builders tell me it did not absorb moisture the way Portland cement does. It seems like we need to rethink what we are making our concrete foundations and slabs out of.

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