Is the House Structure Made of Precast Slabs?

The house structure is not necessarily made of precast slabs. To determine whether a house uses a precast slab structure, a comprehensive analysis combining the construction era, structural form, and physical characteristics is required. Details are as follows:

I. Relationship between Different Structural Forms and Precast Slabs

1. Brick-Concrete Structure:
   The floor slabs of brick-concrete structure houses may be precast slabs or cast-in-place concrete slabs. Urban residential buildings from the 1970s to the 1990s were mainly brick-concrete structures, among which precast slab floors were relatively common. However, not all brick-concrete structures used precast slabs.
2. Frame Structure or Shear Wall Structure:
   Slab buildings often adopt these structures. The floor slabs and walls are usually cast-in-place concrete or a combination of brick and concrete, with strong integrity and excellent seismic performance. The use of precast slabs is extremely rare.
3. Policy Differences between Cast-in-Place Slabs and Precast Slabs:
   After 2003, the state prohibited the use of precast slabs in newly built commercial housing and required the use of cast-in-place slabs to enhance structural safety. Therefore, commercial housing built after 2003 can basically be ruled out as having a precast slab structure.

II. Typical Characteristics of Precast Slab Structures

1. Construction Era:
   Precast slab buildings are mostly found in old residential buildings built from the 1970s to the 1990s, especially those built before 2003, which have a higher probability of using precast slabs.
2. Physical Characteristics:
   • Ceiling Cracks: Regular cracks parallel to the slab joints often appear on the ceilings of precast slabs because the joints between slabs are prone to cracking.
   • Knocking Sound and Vibration Transmission: When knocking on the floor slab with a hard object, a precast slab will emit a clear 'ding-ding' sound, and the vibration is transmitted unidirectionally. In contrast, a cast-in-place slab produces a dull sound, and the vibration spreads widely.
   • Floor Slab Holes: Some precast slabs have circular holes with a diameter of about 8 centimeters in the middle, which are used to reduce self-weight or for running pipelines.
3. Wall Structure:
   If a house has no beams or columns and relies solely on walls for load-bearing, and there are obvious gaps between the floor slab and the walls, it is mostly a precast slab structure.

III. Summary and Recommendations

Precast slab structures have gradually been replaced by cast-in-place slabs due to their long construction era and relatively weak seismic performance. To confirm the type of house structure, a preliminary judgment can be made by observing the construction era, ceiling cracks, knocking sounds, and other characteristics, or a professional institution can be contacted for structural testing to ensure living safety.