Is one allowed to support schach by placing beams on top of the schach and under it. If one can how much? and how wide.
If the width of the beam is less than 3 tefochim (24 cm) one can even sit under it but if the width is more than 3 tefochim one cannot sit under the beam
O:CH 632:1 & Mishnah Berurah 3