Introduction
Mold, mildew, and fungus refer to the same thing. If something gets wet and stays wet, mold will grow. The average time a material must be wet for mold to grow varies. A minimum of two to three days can be sufficient.
Molds secrete enzymes that break a material down into sugar. Mold’s roots absorb the sugars. It’s a stinky process. Metabolites are produced that saturate the building materials and make them smell moldy. The compounds responsible for the odors are called microbial volatile organic compounds (mVOCs). This is not to be confused with mycotoxins. MVOCs are not from mycotoxins.
Once mold has enough food to support its basic life functions, it may produce mycotoxins. Toxins are solids, not gases, substances a mold secretes and slathers itself with to protect it from other organisms. Every mold is capable of producing mycotoxins. It requires energy to produce them. A mold won’t produce toxins unless it is required for survival.
Some believe dry mold is dead. A gardener knows it as over-wintering. Mold goes dormant, waiting to get wet again. Dry spores remain intact and can be dispersed when disturbed by air currents or vibrations. Dry (dormant) mold can be a hazard.
What Can It Do to Me?
All molds are allergenic and potentially toxigenic. Response depends on a person’s immune system, dose, and the duration of exposure. Chronic exposure may lead to allergies or asthma in otherwise healthy people. Dead (non-viable is the correct term) spores are still of concern. Allergens and toxins are not neutralized with chemicals. Symptoms of exposure to mold and moisture include:
- allergies
- cold and flu symptoms
- burning eyes and itchy skin
- difficulty breathing
- dry, hacking cough, sore throat
- headache
- nosebleeds
- fatigue
The BIG 10
This ebook contains excerpts from What Your Builder Should Know: Best Practices for Building a Healthy Home. You can order it on Amazon and wherever you order books. It contains additional resources and covers the important things to consider when building a healthy house - not just ones that prevent mold.
The ebook you are reading contains updates, changes, and additions not found in that paper back. The paper back version is recommend to learn more about other, non-mold, elements to consider when building a healthy home. Each step of construction will be covered in this ebook, with explanations and suggestions and mold proof - construction tips.
Before we dive in, here a summary of the Big Top 10.
Top 10 Things to Prevent Mold
1. Wear big boots. Do not have a basement or crawlspace. Build on a concrete slab. Design and build so that there is four inches or more between the bottom of the siding (top of the slab) and the ground after the landscaping is added.
2. Install an automatic shut-off to shutoff the water automatically f if there is a plumbing leak.
3. Inspect wood as it arrives. Measure wood with a moisture meter. Readings should be 19% or less. If the readings are greater than 19% or wood looks as if it has mold, don’t accept it for delivery. After you accept it, store wood so that it stays dry.
4. Wear a big hat. No flat roofs. Make it a pitched roof. The more portals over patios and windows the better. Flash around doors and windows, sidewalls, chimneys, and skylights..
5. Flash the windows the right way. It’s rare you see a builder flash windows the proper way. It’s one of the most common reasons for mold in new buildings.
6. Avoid house-wrap. Install two layers of traditional Grade D building paper. If code requires housewrap, put housewrap on first, then cover it with a layer of building paper.
7. Use batt insulation. Avoid blown-in insulation which inhibits drying if a window leaks.
8. Ventilate. Install an ERV or HRV. Install a system of ductwork dedicated to the ventilation system. (Don’t expect to use the same duct work the air-conditioner or heater use. Don’t use bathroom and kitchen fans for make up air or as ventilation.)
9. Prohibit paper-faced drywall. Use Denseglass (fiberglass faced gypsum board).
10. Discuss with your builder how to build showers. Inspect shower bladders as they are being built. Avoid walk-in showers or slop the tile towards a drain at one side of the shower. There’s no way to flash a walk-in shower so that water can not work it’s way out around the corners.
11. Minimize use of wood. Build the exterior walls with Fox Block or a similar, non-organic material. Use metal studs. Use plastic 2x4s as needed for door and window frames and such (where something needs to be attached to the block).
Wear big boots.
- Do not have a basement or crawlspace.
- Build on a concrete slab.
- Install a vapor barrier before pouring the concrete.
- Design, build, and pour such that there is a minimum of four inches between the bottom of the siding and ground after the landscaping is finished. Leave room for landscaping next to the house such that there remains 4 inches of clearance when the house is finished.
What Can Go Wrong Here
The builder may worry that the vapor barrier will be damaged when the concrete is poured and therefore put sand down as a couchin. Sand holds moisture.
If a vapor barrier is not installed correctly, moisture evaporates into the house. This can cause mold to grow under carpet in places with less ventilation, such as closets. If the vapor barrier was not sealed around penetrations at plumbing pipes and electrical conduits, mold odors, radon, and pests can get inside.
Recommendations
Install a vapor barrier before the concrete is poured. Put the vapor barrier on top of a bed of coarse gravel. Seal the seams and penetrations around pipes with the sealant tape supplied by the manufacturer of the vapor barrier. It should be 15-ml-thick polyethylene in compliance with ASTM 1643-94, Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs. The vapor barrier should be put over a bed of six to eight inches of clean, dry, 1/2-inch coarse gravel (no fines or p-gravel). Overlap the seams six inches and seal the seams with the sealant tape supplied by the manufacturer of the vapor barrier material. Lap the vapor barrier over the footing and seal it to the foundation. It needs to be watertight. Vapor barrier (retarder) products include Perminator® 15 Mil. Order the sealant tape that goes with it. W.R. Meadows (800) 342-5976 Stego® Wrap Vapor Barrier (15-Mil)
Landscape should slope away from the foundation. Water should drain away from the house around the perimeter.
Dirt, rocks, lawn, and other landscaping must not be next to the house higher than what is required to maintain at four inches of clearance between the bottom of siding and soft grade (landscaping) and two inches of clearance between the bottom of siding and hard grade (sidewalks, driveways, patios).
Install an automatic shut-off
Install an automatic shut-off to shut the water off if there is a leak. Suppliers include: WaterCop®, DIYcontrols.com, and FLO-n-STOP.™
If you're looking for smart monitoring and remote control:
- The DIYControls (FloLogic) is a standout for its flow detection accuracy, Wi-Fi features, and strong build—ideal for modern, connected homes.
If you prefer dependable, sensor-based shutoff:
- WaterCop is a trusted option known for reliability and integration with automation. A solid choice if you value proven performance and long-term durability.
If your priority is simplicity and budget:
- FLO-n-STOP delivers straightforward shutoff and an alarm, without willful complications—great for basic protection setups.
Check on-line. There’s always some new and innovative product being introduced on the market. Simpler is better.
Inspect wood as it arrives.
- Buy a moisture meter. Measure wood with a moisture meter as it’s delivered. Readings should be 19% or less. If the readings are 20% or greater or the wood looks as if it has mold - don’t accept the wood.
- After you accept wood, store it to keep it dry. Put it on pallets and cover with a trap.
- Have a Moisture Management Plan. Make sure everyone knows and follows it.
What Can Go Wrong Here
Most builders don’t inspect wood for mold or moisture content when it’s being delivered. Wood may arrive damp or moldy. Wood may get wet if uncovered, and it rains before the roof is put on. A builder may treat the framing with an antimicrobial or paint it with an antimicrobial paint. This does not remove or prevent mold and can cause new problems.
Recommendations
Prohibit OSB (Orientated Strand Board type plywood). Specify plywood - CDX grade plywood or AdvanTech™ for subfloors, walls, and the roof decking. If CDX plywood gets wet, it takes longer for mold to grow compared to OSB. AdvanTech™ is made water-resistant by adding polyurethane.
Use a moisture meter to check wood as it is delivered. Send damp or moldy wood back to the supplier. Store wood to keep it dry. Make sure the builder has designated a place to store wood to be covered and protected from rain and snow.
Create a moisture management plan and keep it on-site. It should state the following:
- Do not accept damp wood (moisture readings of 19% or higher) or water-damaged wood (stained or discolored.)
- Store wood covered on a pallet, even if it’s sunny. And cover it with a tarp.
- If it rains before the roof is on, and the framing is not dry in two days, stop work and bring in fans to expedite drying the wood framing. If visible mold or staining is present, stop work and clean the wood after it is dry (less than 19%). Lightly sandblast the wood. A wire-brush or sander may be used. If a significant amount of wood has mold, consider cleaning it using dry ice blasting. Pellets of dry ice are abrasive and clean the wood. The pellets, made of carbon dioxide, evaporate after being used. Sandblasting makes a mess and is not recommended. Soda blasting is not recommended.
- Do not enclose the walls with insulation and drywall if the moisture readings of wood are greater than 19%.
Want to know more?
Get the Ebook
It covers the rest of the Big Top 10 and more.
Disclaimer
The post is designed for educational purposes only. Our goal is to provide information and scientific data as to the potential hazards in the home or office. All the factors to be considered are beyond the scope of this post. We do not assume responsibility for choices or decisions made including those regarding mitigation. The principles presented here should empower the reader to make informed choices. Book a consultation.