The plaintiffs pleaded and presented evidence on two theories of liability under G. L. c. 93A: first, that the defendant had rented them a condemned unit, see 940 Code Mass. Regs. 3.17(l)(a)(l) and (2) (1978), and second, that he failed, after notice, to remedy violations of the State Sanitary Code, which endangered or materially impaired their health and safety. See 940 Code Mass. Regs. 3.17(l)(b)(l) and (2) (1978). The judge did not make detailed findings of fact on the c. 93A claims as required by Mass.R.Civ.P. 52(a), 365 Mass. 816 (1974). What he did find (essentially summarized above) dealt expressly only with the plaintiff’s first theory. He correctly *956concluded that the defendant had violated c. 93A by renting the plaintiffs a condemned dwelling unit, a conclusion compelled by the requirements of 940 Code Mass. Regs. 3.17(l)(a)(l) and (2). Accepting the defendant’s testimony that he inspected the dwelling units before purchasing the building, the judge reached the conclusion that the defendant was “chargeable with notice” of the existing violations when he rented the second floor apartment to the plaintiffs. The judge’s decision not to multiply damages was based on his conclusion that the defendant had a “misunderstanding” of the requirements of the applicable law. That decision appears to have been based principally on (a) the judge’s acceptance of the defendant’s testimony that, when he rented the apartment, he had not been aware of the condemnation order;4 and (b) the inference apparently drawn from the defendant’s testimony that, although he may have been aware of the existing violations, he thought he could still rent the apartment and take a reasonable time to correct the conditions that rendered it uninhabitable.