12 Tips for Buying or Renting A Mold-Free Home

Look out for these construction and moisture management defects to succeed in buying or renting a healthy, mold free home. 

Inspect the roof design with an eye towards drainage

Water follows gravity. Consider the following:

  • Do valleys come together creating an area that will store water rather than drain it away? 
  • Does a roof slope send water towards an adjacent wall? 
  • Is there any signs of discoloration or variation in color or texture?If water cannot flow freely away from building walls, trapped water can quickly become a hazard that can wick into the walls and saturate interior wall cavities, producing water damage and mold. In climates with snow accumulation, these areas where snow also can become trapped are major sources of potential or concealed water damage and mold.

These types of poor design details will fail and result in water accumulation and leaks over time.

Inspect roof design

Check drainage around the outside of the structure

Water flows downhill. Water should never be allowed to flow toward a structure.

  • Notice neighbors – is their property draining toward yours?

Grade slope away from foundations should be a minimum of 6″ in 10ft. In new construction the slope away should be even more as ground adjacent to the foundation has been disturbed and will settle over the next 10 years. What was once a slope away could turn into an avenue for water to enter the foundation over time.

Check water drainage

Check all gutters & downspouts

Gutters and downspouts with long extensions away from the structure are an essential component of moisture management.

Water should always drain away from a structure

Check clearance measurements

There should be a minimum of 6″ of clearance from the ground to the start of floor framing or exterior wall finishes. I suggest 8″. This often means an partially-exposed foundation wall. 

Measure the clearance

Look for roof overhangs

The larger, the better. Your roof acts an umbrella over your structure. Shallow or non-existent overhangs are known to be associated with high incidence of water damage in outside walls.

Larger roof overhangs are best

Only use solid sheet metal ductwork

Remember that homes with flex duct throughout can never be effectively cleaned. Ducts collect dust in the air, which can be a food source for mold. They should be cleaned, on average, about every 8-10 years, depending on circumstances. 

Only use solid sheet metal ductwork

Any new house should have clean ductwork

Ask to remove some registers and check yourself with a Swiffer cloth. Ask to see the filter. Walk away if a new house has debris in ductwork. Debris in ductwork on new construction is a sign of very careless work and negligent oversight. Silica from drywall dust is also highly toxic. Drywall work should never be done with the HVAC system running which will bring that dust into the system. Silica dust from drywall work is very difficult, if not impossible to remove, as the dust is very fine.

If precautions were not taken to prevent the HVAC from being contaminated during the construction process, there’s likely to be many other defects, oversights, poor construction and deficits due to lack of attention to detail, that are much harder to find easily. Consider debris in ductwork a red flag and walk away. If builders realize that people are noticing, they may start taking precautions.

Avoid HVAC systems in unconditioned spaces

These include attics, garages and crawl spaces. Ductwork should be in the conditioned space as well. If ductwork must go into an attic or crawlspace it must be very well sealed and insulated.

Check for bathroom exhaust fans

Never buy a home without exhaust fans (unless you will install one ASAP). Size exhaust fans correctly for the room and length of duct run. (Yes, there are calculations to do!) Insulated ducts to exterior. Install timer switches to ensure bath exhaust fans are used for at least 30 minutes after bathing or showering.

Check routing of all exhaust fan outlets

These include bathroom fans, dryers, and kitchen exhausts. Solid duct is best, with few elbows and only short, direct runs to a wall or roof. Do NOT put exhaust outlets next to air intake vents!!! (I can’t believe I had to write that…but this common error is everywhere!) Warm moist air wants to rise and will be drawn into the attic space when exhaust outlets are located next to soffit vents. Expect mold to grow in these attics over time. NEVER accept bathroom, kitchen or dryer exhaust fans dispelling air into the crawl space, basement, attic. 

Look where exhaust fans outlet

Ask to see the construction details for the foundation for new construction

Know that any foundation type can have a moisture problem including slab, crawl space and basement foundations. Crawl spaces should never have exposed dirt floor. Any soil which is a part of enclosed living space, must be encapsulated with a vapor barrier with all seams sealed. Also the vapor barrier must be sealed to the crawl space walls. Make sure exposed vapor barriers in crawl spaces are protected to avoid holes and breeches to this important protection layer.

Pay attention to foundation details

Be cautious of particle board as it often off-gasses formaldehyde

Fully evaluate all pros and cons of any chemicals, biocides or sealants and other building products that might be suggested for new construction or already installed in buildings. Be wary of cabinet materials, shelving and closet doors which are often made of particle board or other substrates which may off-gas formaldehyde.

NOTE: Particle board is NOT OSB (Oriented Strand Board). These are different products. OSB is a structural material while Particle Board is not. 

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Get your questions answered!

Cheryl Ciecko, AIA, ALA, LEED AP, is a 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.


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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.