The Shulhan Aruch (Hoshen Mishpat 381) addresses a situation where a bench breaks because it could not contain the combined weight of those sitting on it. If four people sat on a bench, and then a fifth person sat down, causing it to break, that fifth person bears liability for the damage. Since the bench was able to contain the weight of the first four people, it was the fifth person who caused it to break, and thus he bears liability.
However, if the five people sat down together, simultaneously, causing the bench to break, then they all share liability. Since they caused the damage collectively, and no individual can be singled out at the exclusive cause of the breaking, they must all pay for the damage; each of them must pay for one-fifth of the damage.
These Halachot apply only if the bench was capable of withstanding the weight of four people indefinitely. However, if the bench was able to withstand the weight of four people for only a limited period of time, then if a fifth person sat down and caused the bench to break immediately, they all share liability. Since the bench would have broken anyway, and the fifth person only caused the breaking to occur sooner, they all share the blame. The fifth individual bears sole liability only if he prevented the other four from getting off the bench. Meaning, if the four people decided to stand up when the fifth arrived, but he insisted that they remain seated on the bench, then he bears sole liability. Since he prevented the other four from leaving the bench, he is to blame for the damage.
These are the rulings of the Shulhan Aruch on this subject. The Rosh (Rabbenu Asher Ben Yehiel, Germany-Spain, 1250-1327), however, held differently, and his view may yield important repercussions when such a case is brought before a Bet Din. According to the Rosh, there is no liability for damage caused by sitting on a bench. The Rosh compares this case to the case of a borrowed animal. If the borrower used the animal in a normal fashion, and the animal died ("Meta Mahamat Melacha"), the borrower does not bear liability, since the damage occurred as a result of normal usage. Similarly, the Rosh argued, sitting on a bench is the normal manner of using the bench, and thus if a bench breaks when a person sits on it, he does not bear liability. The only exception would be a case of an obese person who sits on a bench, which constitutes abnormal usage of the bench and thus the individual would bear liability.
Although the Shulhan Aruch does not accept the Rosh’s ruling, the view of the Rosh is significant because a person can claim in court, "Kim Li Kemo Ha’Rosh" – meaning, that he accepts the position of the Rosh. In effect, then, a person who breaks a bench by sitting on it can exempt himself from payment by insisting that he follows the Rosh’s view.
Summary: If several people sit on a bench, and when another person comes and sits his extra weight causes the bench to break, he is, according to the accepted Halacha, required to pay for the damage. However, given the different views among the Halachic authorities in this regard, the individual can excuse himself from payment by claiming that he follows the other view.
