Bava Batra, Chapter Three Mishnah Eight
Mishnah eight deals with permitted and not permitted damages that an individual might create to the public domain.
1) One may not hollow out a space underneath the public domain [such as] cisterns, trenches or caves.
a) Rabbi Eliezer permits it if it is such that a wagon loaded with stones can [safely] go over it.
2) Projections and balconies may not be built into the public domain; but if a man wishes to build a [projection or balcony] he may withdraw [his wall] within his own domain and build out from it.
a) If he bought a courtyard in which were already projections and balconies, his right to maintain them may not be disputed.
Section one: One may not dig out a space underneath the public domain lest the ground crash in. According to Rabbi Eliezer if the ground is strong enough one may do so.
Section two: One may not build projections of any nature into the public domain, but one may pull back his property and build a projection out from there. If he bought property that had such projections we assume that they were not built on public property and we do not make him remove the projections.
Questions for Further Thought:
· Why might one have thought that it is forbidden to build a projection or a balcony even within ones own property?