Multimeters can be used for a variety of applications. But the primary use here would be for testing your underfloor heating systems. Not only will the multimeter give you resistance readings. But can also be used to check for any leak to earth. Potentially saving you a lot of time and money. Can also help narrow down where or with whom the fault lies. For example, if four or five tradesmen will be coming onto the project at any point. And a reading is taken after each trades person leaves this can give you a good indication as to where the fault lies both physically and financially.