1. Leaded Paint

Residential use of leaded paint was banned in the United States in 1978. Any house built before that date is likely to have leaded paint in at least some layer of old paint that has since been covered with non-leaded paint. According to the U.S. Centers for Disease Control (CDC), approximately 24 million housing units have deteriorated leaded paint and elevated levels of lead-contaminated house dust. More than 4 million of these dwellings are homes to one or more young children, who are especially susceptible to the effects of lead. If homeowners are selling a house built before 1978, they must comply with a federal law that imposes several notification and disclosure obligations on the sellers.

2. Asbestos

Asbestos was once used in a variety of home construction products, including siding, duct insulation, blown-in attic insulation, vinyl floor tiles and glues, among others. If the product containing the asbestos is intact and will remain undisturbed, homeowners are under no obligation to act. However, if the asbestos is exposed or the product could suffer some damage over time, it needs to be encapsulated — primed and painted with good quality latex paint, for example — or covered (totally enclosed). When the product is deteriorating, homeowners should either repair the problem area, which is pricey but not sky-high, or have it removed, which can be very expensive.

While homeowners should disclose the presence of any asbestos-containing material to potential buyers, they are not legally required to do so in many states or by the federal government. In Massachusetts, for example, sellers are required to disclose the presence of lead paint and urea formaldehyde foam insulation but not asbestos.

3. Mold

Black mold is a potential environmental problem that will scare off buyers quicker than just about any other problem. If the mold is not visible but dampness in the walls, floors, or ceilings is apparent, then mold of some kind is almost certainly growing. In most cases, getting rid of mold is far more costly than preventing moisture from attacking the lumber, sheetrock, ceiling tiles and other wood products that mold spores love. Some molds are toxic, and even those that are not may cause allergic reactions in some people.

A professional mold inspection gives the seller a signed report from before the house is listed for sale. Buyers may choose to conduct their own testing as well, but at least the seller has a better chance of completing a sale with a satisfactory mold report. However, unlike leaded paint, there are no federal regulations for mold inspections or remediation. In 2012, Virginia rescinded legislation regulating licensing for mold inspection and remediation after just one year in effect due to the lack of federal standards.

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4. Foundation Cracks

On average, repairing a crack in a house’s foundation costs about $3,500 but can run as high as $10,000. Most cracks to the foundation are caused by settling, and the first sign can often be a door that no longer closes properly because the door frame has become crooked. Other signs that the house’s foundation may be cracked include cracks in the walls above doorways or where the walls meet the ceiling, sticking windows and cracks in vinyl or ceramic floor tiles. Figuring out if any of these signs indicate a crack in the foundation is a job for a structural engineer. The cost of fixing a foundation crack rises the longer homeowners wait to fix it. Most buyers will shy away from a house with an unfixed foundation crack.