Mold-Savvy Construction and Remodeling

Alex Manning, Clean Air Advice
September 2006

If you are building a new home, or just doing some remodeling, you no doubt have concerns about mold and its possible health effects. Besides expensive damage to your property, mold growth can contribute to poor indoor air quality in your home, potentially resulting in dangerous health problems. For more insight into molds and fungi, and the health problems they pose, read our Mold, Mildew, and Fungi article.

Mold concerns have been getting a lot of attention in the news, not least because of numerous legal cases in which millions of dollars have been awarded because of mold infestation in new construction. But is the mold problem really a new one?

Mold has been a problem for builders since pre-biblical times. Over the millennia, however, the more-successful builders employed a few simple techniques that dramatically reduced the risk of mold in their buildings. As a homeowner, you want to make sure your contractor is building a safe, healthy home for your family. Here are some helpful tips you can use to make sure your new home or addition is mold free:

Keep it Dry

Molds are microscopic organisms that are present virtually everywhere in our environment. Molds break down dead organic materials, such as wood and leaves, and recycle nutrients back into the environment. All that is necessary for mold growth to start on these materials is moisture.

Generally, within 48 hours after getting wet, invisible mold growth has started on wet woods and paper-backed products such as Sheetrock. After about four days, mold growth on surfaces is visible in the form of discoloration, frequently green, gray, brown or black, but also white and other colors.

Because molds digest organic material, they gradually destroy whatever they grow on. Molds also release countless tiny, lightweight spores, which travel through the air. These mold spores provoke allergic reactions in many people, and contribute to asthma attacks. They can also produce dangerous mycotoxins, poisonous substances linked to a variety of serious health problems, some even fatal.

In finished construction, roof and window leaks, plumbing defects, drainage and grading problems, and other sources of water infiltration can trigger the chain of events that ultimately leads to active mold growth. But in new construction, there are some simple steps to take to cut down the chance of mold infestation.

Preventing Mold

Simply put, the best advice is this: Do not build with wet materials. This may present a challenge in certain climates of the United States, especially during rainy times of year, but there are still several steps a prudent contractor can take to prevent or minimize mold growth.

As simple as the advice may be, you'd be surprised how often it goes unheeded. Poor weather conditions, unrealistic construction schedules, and even ill-advised drives for "efficiency" in construction causes many contractors to ignore some of the most basic mold-prevention tips. Sit down with your contractor before building begins, and air your concerns about mold in your home.

Mold spores are always present in both indoor and outdoor air, and they can flourish in any ambient temperature from 40 F to 100 F (4 C to 38 C). But you can have some control over the moisture mold needs, and you can also have some control over the use of organic materials in construction.

Because some moisture is inevitable, either during installation or from condensation, use components that will retain as little moisture as possible. Moisture-resistant materials will cut down on retained moisture. Specify materials that have no organic content as part of your overall mold-resistance strategy. For example, paper facings could support the growth of mold. Some of the new "paperless" gypsum wallboard might be a good alternative. Materials that don't have organic components resist mold.

Of course the use of some organic building material—such as lumber, for example—is unavoidable. Here are some tips to follow to prevent mold growth in these materials:

1.) Keep stocks of lumber, plywood, oriented-strand board (OSB), Sheetrock, and other porous materials in a dry, covered storage area. If the stockpiles are out in the open, and it looks like it might rain, cover the materials with a good tarp, anchored down so that the wind does not blow it off. When the materials are needed, remove them from beneath the cover without allowing the remainder to get wet or damp.

2.) Before installing the materials, inspect carefully for water damage, staining, warping, or initial signs of mold growth. Such signs might be visible patches of mold, or simply the musty odor we associate with mold or mildew. Discard any such materials immediately.

3.) Install a roof or cover the new construction as soon as practical. If the rain is falling, the interior spaces of the building are getting wet. And moisture is one of the key things mold spores need to grow.

4.) If the materials are merely wet, all hope is not lost. Bring in portable heaters and dehumidifiers to thoroughly dry out the wet materials before covering them up or sealing up the building. A contractor can employ a simple moisture meter to make sure the previously wet materials are sufficiently dry to allow construction to proceed.

5.) If, despite these precautions, mold starts to grow on installed building materials, do not attempt to "cover it up" by installing dry lumber or Sheetrock over it. Mold spreads very rapidly in a moist environment, and the wet materials will serve as a moisture source that will rapidly transfer damage to the previously clean, dry materials. Existing mold growth should be cleaned up completely before anything new is added.

6.) Do not try to simply wipe off mold or paint over it. The underlying moisture that is supporting the mold growth will not go away, and the mold will likely reoccur, even after construction is complete. In addition, the materials might already be structurally or functionally damaged, and paint will not cover that up for long. Most mold-infested porous materials must be removed and discarded.

Maintaining a Mold-Free Environment

By following these common-sense practices, your contractor can have you well on the way towards living in a healthy, mold-free home. After the construction is done, make sure to keep your home free from indoor air quality hazards. A good place to start is our Twelve Steps to Improving Indoor Air Quality tips.

Related Articles

• Do You Have a Mold Problem?
• Mold, Mildew and Fungi
• Mold, Asthma and Your Child
• What Are You Breathing?
• 12 Steps to Improve Indoor Air Quality