What should be earhing resistance in house?

Earth ground resistance.

There is not one standard ground resistance

threshold that is recognized by all agencies.

However, the NFPA and IEEE have recommended

a ground resistance value of 5.0 ohms

or less.

The NEC has stated to "Make sure that system

impedance to ground is less than 25 ohms

specified in NEC 250.56. In facilities with sensitive

equipment it should be 5.0 ohms or less."

The Telecommunications industry has

often used 5.0 ohms or less as their value for

grounding and bonding.

The goal in ground resistance is to achieve

the lowest ground resistance value possible

that makes sense economically and physically.