Though defendant poses seven questions for our consideration, the appeal raises but one question, and that is whether the court’s finding that defendant prevented plaintiff from completing its performance of the contract is supported by competent evidence. If it is, the finding is conclusive, Williams v. Pilot Life Insurance Co., 288 N.C. 338, 218 S.E. 2d 368 (1975), and defendant is precluded from using plaintiffs failure to perform the contract either as a defense to the case or as the basis for a counterclaim. This elemental proposition has been enforced by the common law since the days of Lord Coke, if not before. Cape Fear and Deep River Navigation Co. v. Wilcox, 52 N.C. 481 (1860).

*650There was testimony to the following effect: After plaintiff installed the flooring on 4 October 1982 and Dr. Wilson complained of some scratches on the vinyl, plaintiff had the floor buffed and waxed with two coats three days later, but the scratches were still apparent and on 13 October 1982, though maintaining that the flooring was not defective or improperly done, plaintiff agreed to replace the flooring at no additional charge in order to satisfy defendant and the building owner. Just three days later on 16 October 1982, plaintiffs installer went to the clinic building to do the reflooring, but defendant’s president refused to let him do the job, told him to leave the premises, and later had the flooring replaced by someone else.

This evidence amply supports the judge’s finding that defendant prevented plaintiff from fully performing the contract, and the judgment appealed from is therefore affirmed.

Affirmed.