Pal-Kal (Hebrew: פל קל) was a construction method for concrete ceilings, invented by engineer Eli Ron in the late 1970s (Israel Patent No.
The Pal-Kal method offered an easier, faster, and cheaper solution for casting ceilings compared to traditional reinforced concrete slabs.
However, certain applications of this method were proven to be extremely dangerous, and the use of non-standard Pal-Kal ceilings was the main cause of the collapse of the Versailles wedding hall disaster.
Construction process of Pal-Kal ceilings began with the pouring of a very thin layer of non-structural concrete with minimal reinforcement.
Above or into this initial concrete layer, the galvanized boxes were inserted in the shape of the letter 'ח' (Chet in Hebrew).
In 2001, a Pal-Kal ceiling collapsed while guests were dancing on it at the Versailles wedding hall in Jerusalem, resulting in the death of 23 people.
Nowadays, most municipalities require annual safety checks to detect potential problems in Pal-Kal structures.