How to Identify Prefabricated Floor Slabs in Houses

To determine whether a house has prefabricated floor slabs, you can use the following comprehensive methods:

1. Observe the construction year According to the evolution of building codes, houses built before 1998 are mostly constructed with prefabricated floor slabs, especially older public housing and unit welfare housing. After 2003, the state explicitly prohibited the use of prefabricated slabs in newly built commercial housing, so commercial housing built after 2003 generally uses cast-in-place slabs. If the house was built between these two time points, further confirmation is needed using other methods.

2. Examine the structural characteristics of the floor slabs Prefabricated slabs are assembled from prefabricated concrete components, presenting a regular block structure on the surface. There are obvious gaps between the slabs, typically 1-3 centimeters wide. Cast-in-place slabs, on the other hand, are formed through integral pouring, resulting in a smooth and flat surface without obvious splicing marks. Additionally, the ceiling of prefabricated slabs may develop regular cracks parallel to the slab joints due to settlement or temperature changes, while cast-in-place slabs tend to have irregular, net-like cracks.

3. Tap the floor slabs to identify their nature by sound Gently tap the floor slabs with a hard object (such as a key or small hammer):

• Prefabricated slabs: Produce a clear, long-lasting sound similar to tapping a hollow wooden board; the vibration传导 (transmission) is unidirectional, meaning the vibration only travels along the direction of the slab joints.
• Cast-in-place slabs: Emit a dull, short sound similar to tapping solid concrete; the vibration spreads evenly in all directions without a clear directional pattern.

4. Check the original design drawings If you can obtain the original design drawings of the house, you can directly check the floor slab structure description. If the drawings are labeled as "prefabricated hollow slabs" or "prestressed hollow slabs," it confirms the use of prefabricated slab structures; if labeled as "cast-in-place reinforced concrete floor slabs," it indicates a cast-in-place structure.

5. Observe the wall and beam-column structures Houses with prefabricated slabs typically have no beams or columns, with the walls directly bearing the weight of the floor slabs. As a result, the wall thickness may be relatively thick (commonly 24-centimeter brick walls). Houses with cast-in-place slabs, however, have clear beam-column structures, with the floor slab weight transferred to the foundation through the beams and columns. The walls only serve as enclosures and may be thinner (commonly 18-20-centimeter lightweight walls).

6. Look for distinctive features of the floor slabs Some prefabricated slabs have circular holes about 8 centimeters in diameter reserved during production (used to reduce weight or for pipeline installation). If such regularly arranged circular holes are found on the surface or bottom of the floor slabs, it confirms the use of prefabricated slabs. Cast-in-place slabs do not have such features.