The flooring I am trying to measure is pre-finished; will this affect the readings I get?

This depends on the type of finish. As long as the finish is dry and is not a metallic finish the meter reading will be unaffected. If there are metallics in the finish, the meter will give you a reading that is higher than the true moisture content of the flooring.

Please visit www.wagnermeters.com for more information or call 1.844.829.3335 to talk to a professional.