W. Va. Code § 55-5-2: Valuation of improvements made by defendant before notice of title.

If the jury be satisfied that the defendant, or those under whom he claims, made on the premises, at a time when there was reason to believe the title good under which he or they were holding such premises, permanent and valuable improvements, they shall estimate in his favor the value of such improvements as were so made before notice in writing of the title under which the plaintiff claims, as they are at the time such valuation is made.