Homes that have undergone do-it-yourself (DIY) renovations may include improperly sealed showers, unvented exhausts, or unpermitted construction that affects moisture control. Kitchens, bathrooms, and basements are especially vulnerable when renovations are not done to code or without mold-aware design.

Also be cautious of layouts that funnel outside air, moisture, or pollutants into the main living space. Examples include units with outdoor hallways, indoor fountains, or storage rooms that open directly into sleeping areas. Spaces that lack entryway separation (mudrooms, transition zones) may allow contaminants to be tracked into the home, which is particularly problematic for those managing exposure to outdoor molds, pollen, or toxins.