§ 174. Repairs and cleanliness. The owner shall keep all and every part of a dwelling and the lot on which it is situated in good repair, clean and free from vermin, rodents, dirt, filth, garbage or other thing or matter dangerous to life or health; but the tenant shall also be liable if a violation is caused by his own wilful act, assistance or negligence or that of any member of his family or household or his guests.