This page within Virginia Tort Case Law is a compilation of cases reported by the Virginia Supreme Court and summarized by Brien Roche dealing with the topic of Warranties-Implied Warranty of Proper Workmanship.
1978 Bruce Farms, Inc. v. Coupe, 219 Va. 287, 247 S.E.2d 400.
Contract to perform service necessarily implies covenant to perform according to prevailing standards of competency.
1950 Mann v. Clowser, 190 Va. 887, 59 S.E.2d 78.
Where person holds himself out as specially qualified to perform work of particular character, there is implied warranty that work which he undertakes shall be of proper workmanship and reasonable fitness for its intended use. Same applies in construction contracts.
For more information on warranties see the pages on Wikipedia.