In-floor safes provide terrific security from theft, but most customers decide against buying one when they learn about all the negatives.
1) Difficult to install: Floor safes are hard to install, especially if you need to cut a hole into an existing concrete floor. Even when pouring a new floor it can be difficult to properly set the safe.
2) Lack of space: If all you are storing is gold or cash most floor safes will give you plenty of room. But for bulkier items like silver or a coin collection or documents you will run out of space quickly.
3) Inconvenient to use: Getting down on hands and knees to unlock a floor safe is awkward. Reaching down below floor level into the safe is worse. Even if your knees and back allow you to do that now, will they still be OK in five or ten years?
4) Water and moisture problems: Most floor safes are not water-proof around the door, so a broken water heater, sewer backup, water from a fire hose or heavy rain can flood a floor safe and damage its contents. A rising water table can flood the safe from below ground if there are cracks in the welds. Floor safes tend to be more damp than above ground units, so they are more likely to develop odors and mildew.
5) Rust: When safes are installed so that there is contact with damp sand, most can rust through in just a few years. A plastic or fiberglass safe body can prevent this problem.
6) Lock problems: Since the lock is below floor level, it is easy for sand and dirt to get inside it. That will cause problems for any kind of lock.
7) You can’t take it with you: When you sell your house you will almost certainly need to leave a floor safe behind and buy a new one.
All that being said, the high security provided by floor safes make them appropriate for some folks.