Landlords, brace yourselves: Your tenants are likely going to ignore some of your rules. Luckily, the most common offenses center around decorating and aren’t too serious.

The top offense? One in four tenants make holes in walls (often from nails). That offense is most common among renters aged between 25 to 34, according to a new survey of U.S. tenants conducted by iProperty Management.

Also, 19% of renters surveyed say they’ve completely redecorated a property without their landlord’s permission.

Interior decor aside, tenants also have hidden pets from their landlord. Male tenants may lie about this one the most. Sixteen percent of male renters confess to keeping a pet in their property without their landlord’s knowledge, compared to only 10% of females, the survey shows.

The survey also found that renters are not just relying on submitting maintenance requests to their landlords. They’re also taking matters into their hands—and it can get costly when they do. American renters say they’ve spent an average of $480 on maintenance and improvements—requests that usually are covered by the landlord. Men tend to spend more, an average of $528, about $100 more than women. Broken down by age, renters aged 35 to 44 invested an average of $586 in the maintenance and improvement of their rental, more than any other age group.

Renters report paying to replace old fixtures, and 61% say they’ve spent money on maintenance of interior decorations. Fifty-two percent of renters say they spent money on maintaining their garden.

Overall, 28% of renters say they think there are too many rules for tenants. Sixteen percent believe those rules are too strict. Further, 33% of renters believe tenancy rules make their property feel like less of a home.

The following are the rules most often broken by tenants, identified by iProperty Management’s survey:

1. Making holes in walls: 25%
2. Redecorating: 19%
3. Secretly replacing damaged furnishings, fixtures, and fittings: 13%
4. Keeping a pet in the property: 12%
5. Making a late rent payment: 10%
6. Smoking indoors: 7%
7. Changing locks: 6%
8. Subletting a room or the whole property (long or short term): 5%
9. Removing or disabling fire or carbon monoxide alarms: 4%