Today the main element in structures design is considering the vulnerability against hazards caused by seism. Therefore all structural elements are designed according to specific criteria and standards to resist against seismic forces.

Basically, slabs and structural roofs are not considered as resistant systems against lateral forces and they only transfer them to the bearing parts. Regarding this fact, integration and rigidity of the roof ensure a proper and complete transfer of the seismic forces.

The most important defects of block and joist ceilings during seism are falling of earthenware materials, detachment of the yonolit (poly styrene) phase, falling of the roof downer covering materials, and improper function in transferring lateral forces, which has been overcome in steel composite roofs. In other words, in the new method of steel composite roofs the risk of covering material falling would be minimized due to the roof integration and thorough consolidation.

Totally, block and joist ceilings have considerable rigidity in comparison to the former Jack arc ceilings, but rigidity of steel composite roofs is definitely more than block and joist ceilings. In this method, steel composite roof creates a totally integrated surface that has an appropriate rigidity in turn to transfer seismic force to the bearing elements.