422. No Walls, No Lintel

Tefillin, Mezuzah v’Sefer Torah 6:3

A portico with three walls and a roof does not require a mezuzah even if there are two pillars on the fourth side. These pillars are designed to support the roof, not as a doorway. Similarly, if a roof stands on pillars without walls, it does not require a mezuzah even if it is shaped like a house. This is because the pillars are designed to support the roof and not as doorposts.

Tefillin, Mezuzah v’Sefer Torah 6:4

If a house has a doorposts with an arch on top instead of a lintel, then if the doorposts are at least ten handbreadths high (about 30 inches), it requires a mezuzah. If they are not ten handbreadths high, it does not require a mezuzah because of the absence of a lintel.