Five-hole Prefabricated Slab House

The five-hole prefabricated slab house was a widely used architectural form in the 1990s, but it had numerous issues and has gradually been replaced by the new-standard prestressed hollow slabs with better performance.

I. Basic Structure and Characteristics

The five-hole prefabricated slab, also known as the prefabricated five-hole slab, has five through-holes in the middle. The hollow positions do not bear loads, which can reduce weight and save costs. Its standard width is 50 centimeters, and the main thicknesses are 12 centimeters and 15 centimeters. The mainstream length specifications range from 2 meters to 4.2 meters, with a maximum span not exceeding 4.2 meters. The thickness directly determines the load-bearing capacity; a 12-centimeter slab can bear 200 kilograms, while a 15-centimeter slab can bear 300 kilograms. For kitchens and bathrooms, it is recommended to use thicker solid slabs to prevent moisture and cracking. In the southwest region, it is necessary to select Grade IV load-bearing slabs with reinforced steel bars thickened to specific specifications.

II. Main Issues

1. Quality Issues: The production is rough, with insufficient reinforcement and an unbalanced sand-to-gravel ratio, leading to poor quality and a short service life.
2. Safety Hazards:
   • The foundation excavation depth is shallow, lacking the protection of ring beams and the support of load-bearing concrete columns.
   • The prefabricated five-hole slabs are directly connected to the walls, with limited connection dimensions, usually only accounting for one-third to one-half of the wall thickness, and without riveting measures. In the event of natural disasters such as strong winds or earthquakes, the prefabricated five-hole slabs are prone to detaching from the walls, causing house collapses and casualties. For example, in the Wenzhou area, due to the impact of typhoons, a relatively high proportion of casualties occurred in houses built with prefabricated five-hole slabs that collapsed due to the wind; in the Wenchuan earthquake, a large number of brick-concrete structure houses collapsed, and the public raised many criticisms against the prefabricated prestressed circular-hole slabs (prefabricated slabs).
   • There is a lack of integrity. Once a prefabricated slab falls somewhere, it may trigger a chain reaction, causing the entire house to collapse. Moreover, without rigid member support, buried individuals cannot be effectively protected, and the chances of survival are small.

III. Development Status

Recently, the CECS standard has released a draft for solicitation of comments on the "Technical Specification for the Application of Prestressed Concrete Hollow Slabs." Compared with the traditional "five-hole slabs," the prestressed hollow slabs in the new specification have significantly improved performance.