Homeowners and real estate agents know how to attract buyers and ensure a successful sale: improve curb appeal, paint, declutter and ask a reasonable market price. While these are easy steps to take, houses can have difficult to discover problems that can significantly lower their price. In some cases, the problems are so severe that they can stop a sale completely.

24/7 Wall St. analyzed several of the pitfalls owners should know about and that discerning buyers can discover. All states have mandatory disclosure laws that require home sellers to disclose any material property defect. In some cases, the sellers may not be aware of a defect they have lived with for years and are not trying to hide the issues. There may be problems that existed before the current owner bought the home or that were added inadvertently as a property was altered. Failing to disclose these can lead to lawsuits when the defects are eventually found. Material defects regulations can vary from state to state, which can further complicate the process of purchasing of a new home.

Most home buyers and home sellers are likely to pay the few hundred dollars for a home inspection, which can save both parties money and grief later. This is particularly true for older homes. Still, even good house inspectors have limits to what they can inspect. Often, they are unable to check inside or under the structure and are restricted to what they can see or reach. Not many buyers or sellers opt for a more thorough inspection, which is much more expensive and time-consuming.

Material defects in a house can affect the sale price substantially, or even be deal breakers. They often involve water issues such as old pipes, as well as hazardous materials and structural problems, but are hardly limited to that. When asked to name some of the problems, a home inspector might or might not find on a property that could cause a buyer to refuse to go through with the purchase, Frank Lesh, executive director at the American Society of Home Inspectors (ASHI), said, “A severe structural problem. For example, leaning or cracked foundation, excessive mold, or water damage.”

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Nick Gromicko, founder of the International Association of Certified Home Inspectors (InterNACHI) told 24/7 Wall St. that about one-quarter of the home inspection industry is related to testing for mold because it can cause such serious health problems. “Mold is a health issue which many young families wish to avoid. There is sometimes a feeling that mold will never go away,” added Lesh.

Here then are 10 problems that may make selling a house either more difficult or even impossible.