If a firebox is elevated the hearth should be?

By Federal guidelines a Hearth has to be at least the height of the Firebox if not above the Firebox. If a firebox is elevated a hearth should be of equal height or higher. There may be a loop hole if the Firebox is more than 12 inches off the ground, you may not be required to have a Hearth at this point, but I'm not positive.