Inspection Methods for Prefabricated Slab Houses

Inspection methods for prefabricated slab houses can be comprehensively determined by observing the floor slab structure, checking the construction year, tapping to listen for sounds, examining design drawings, and observing crack conditions.

1. Observing the Floor Slab Structure
Prefabricated slabs typically exhibit a regular block shape with noticeable gaps between slabs. The surface may have slight irregularities due to the joining process. In contrast, cast-in-place concrete floor slabs are formed as a single unit, with a smooth and even surface and no visible joining marks. By comparing the flatness and joining characteristics of the floor slab surface, one can initially determine the structural type.

2. Checking the Construction Year
Prefabricated slab structures were commonly used in houses built earlier, especially in the 1980s and 1990s, due to their high construction efficiency and low cost. In recent years, newly built houses generally adopt cast-in-place concrete structures, which offer better overall integrity and seismic performance. Combining the house's construction year can narrow down the judgment range.

3. Tapping the Floor Slab to Listen for Sounds
Gently tap the floor slab with a hard object (such as a small hammer). Prefabricated slabs, due to their internal hollow spaces or joining gaps, produce a clear and long-lasting sound. Cast-in-place slabs, being dense and gap-free, produce a dull and short sound. If hollow sounds are heard in multiple areas during tapping, be alert to potential issues such as internal hollowing, concrete spalling, or steel bar corrosion, as these defects may affect structural safety.

4. Examining the House Design Drawings
If the original design drawings of the house can be obtained, one can directly check the annotations regarding the floor slab structure type. Drawings that clearly indicate "prefabricated slab" or "assembled floor slab" refer to prefabricated structures, while "cast-in-place slab" or "monolithic casting" correspond to cast-in-place structures. This method is the most accurate but depends on the availability of the drawings.

5. Observing Crack Conditions
Focus on key load-bearing nodes such as the junctions between beams and columns and the joints between prefabricated slabs:

• Through-cracks: Cracks that penetrate the floor slab or wall, possibly caused by foundation settlement or insufficient structural bearing capacity;
• Diagonal long cracks: Commonly found at the joints between prefabricated slabs, possibly caused by poor joining or temperature stress;
• Crack width exceeding 2 millimeters: Exceeds the allowable value specified in regulations and requires further structural safety testing.
  If cracks are accompanied by water seepage, exposed steel bars, or concrete spalling, immediately commission a professional organization for assessment.

Precautions:

• A single inspection method may have limitations, so it is recommended to combine multiple methods for judgment;
• If structural abnormalities (such as severe cracks or hollowing) are found, contact a qualified house safety appraisal organization for professional testing;
• Avoid concentrating heavy objects at the joints between prefabricated slabs during daily use to reduce the risk of structural damage.