10 Ways to Avoid Mold During Construction

Home under construction

Mold is everywhere

Without mold we would not have dirt to grow our food, as mold is part of the decomposition process of organic matter. Mold will grow almost anywhere. The requirements are:

  1. Oxygen
  2. Moisture
  3. Nutrients
  4. Temperatures between 40 and 100 degrees Fahrenheit.

Oxygen and temperatures which are ideal for mold are also ideal for life. Food sources include many materials which are used in the construction of buildings including paper, cardboard, ceiling tiles, wood products, paint, wallpaper, adhesives, insulation, drywall, carpet, fabrics and any material that can collect and hold dust. Dust and dirt are biological materials which also support mold growth, therefore, mold can be found on ANY material, including concrete, masonry, steel including ductwork and plastic. 

Mold-Resistant Materials

Even ‘mold-resistant’ materials can have mold growing on the surface in certain conditions. The food source most overlooked is DIRT and DUST. Mold can actually ride on the back of dust particles…both unseen to the eye. However, water does not belong on building materials and mold should not be growing there either. Moisture to feed the mold can come from many sources also, including bulk water leaks, condensation of water vapor in the air, diffusion through materials and water drawn from other areas due to capillary action.

Follow these simple rules

Materials used in the construction of buildings MUST be protected in storage and delivery before shipment to a jobsite, on the jobsite itself and during construction. Wood materials are particularly vulnerable and poor construction and maintenance practices, along with sustainable energy practices can exacerbate the growth of mold in buildings.

Consider using conscientious suppliers for any materials used, especially wood materials. Require proper practices for receiving, unloading, storage, handling, installation and bracing of lumber and panel products after delivery to the jobsite, to help maintain material quality during construction and for the service life of the building.

10 ways to avoid mold during construction

  1. Inspect lumber upon delivery to the job site. Note any defective materials immediately and contact the supplier to return them. Manufacturers often offer buyers the option of wrapping units or individual pieces with special moisture resistant but vapor permeable protection for transit or storage.
  2. Verify proper grade-marking, moisture content notations (KD19 = Kiln dried to a moisture content of 19% or less). Look for the APA stamp on panel or engineered products. Confirm the moisture content of wood materials with a moisture meter if questions arise. 
  3. Unload lumber in a dry place – not in wet or muddy areas.
  4. Elevate lumber on stringers to prevent absorption of ground moisture and to allow air circulation. Do not store lumber in direct contact with the ground. Materials should be stored at least 4 inches off the ground. 
  5. Cover lumber stored in an open area with a material that will give protection from the elements. Use a tarp or other vapor permeable / moisture resistant material. Polyethylene or similar non-porous materials act as a vapor barrier, so it is important to allow ventilation around the material to prevent condensation on the underside of the covering.
  6. Limit storage time. Only have materials delivered as they will be used. Enclose framing lumber under roof as soon as possible. Enclose the structure as quickly as possible to protect materials. 
  7. If materials do get wet (which is common due to weather) ensure that they are dry enough to be enclosed before construction progresses, using a moisture meter. No sawn wood material should measure more than 19% moisture content. Engineered materials should often be even less, as those arrive at levels as low as 4% moisture content.
  8. Store exterior materials in a covered outdoor area. (e.g. siding, porch flooring)
  9. Store interior items such as flooring, millwork and cabinets in the enclosed conditioned area where installation will occur. It is important to acclimate these items to the finished humidity levels which may be much lower than shipping humidity levels.
  10. Understand the limitations of protective coatings. Know that there is additional protection when lumber comes in paper-wrapped packages or has been treated with a weather protective coating. However, weather-protective coatings are generally effective for only about three to six months. Damage to the protective paper during transportation can reduce its effectiveness, and protection is lost when paper wrappings are removed. House wrap and other moisture management products have a limit to the amount of time they can be exposed to UV to avoid degradation. Check your manufacturer instructions.

Pressure-treated wood is safe and environmentally friendly when properly treated, handled, and installed. Many of the same safety rules for using untreated wood also apply to the safe use of treated wood. Treated lumber should be stacked and stored in the same manner as untreated wood. Refer to the SFPA publication, Pressure-Treated Southern Pine

Here is more information on protection of engineered wood products.

Here is more information on Southern Yellow Pine and managing moisture and mold.

NOTE: Disregard the information on cleaning mold off of wood as it is incorrect. See this blog post to learn more about cleaning wood and other porous materials.

Store your materials wisely on the job site to ensure the best possible start to your mold-free life!

➡️ Access my FREE webinar on mold-aware building

Cheryl Ciecko is an ALA, LEED AP, Licensed Architect who helps homeowners and building professionals create safe homes through online education to prevent mold, water damage, and poor indoor air quality. 


You can find her video masterclasses, online programs, and education subscription options at https://avoidingmold.com/education .


For detailed answers on your specific situation or building project, schedule your appointment for an individual consultation.




The information contained in this presentation is for educational purposes only and is not intended to diagnose, prescribe, treat, or cure any disease, ailment or injury to the body. It is not medical advice. FDA regulations prohibit the use of medical claims in conjunction with the sale of any product not approved by the FDA. Statements made herein have not been evaluated by the FDA. 

Any products, techniques, and/or personal usage tips referred to are not suggested as a replacement for proper treatment from a licensed health care professional. I am not a licensed health care professional and the decision to use or not to use any of this information is the sole responsibility of the listener and/or reader. Everyone is an individual with different body types, different blood types, different body chemistries, and it is important to remember that what works for one person may not work for another person.