Cracks Between Prefabricated House Slabs

Whether cracks between prefabricated house slabs are safe requires case-by-case assessment; some are normal, while others warrant caution.

Normal Cases

• Shrinkage Cracks: During the concrete curing process, water evaporation causes the concrete to shrink, leading to shrinkage cracks. These cracks are typically thinner than a hair strand and are a normal phenomenon resulting from the material properties of concrete. Generally, they do not pose a risk to the structural safety of the house.
• Temperature Cracks: Due to temperature changes, prefabricated slabs expand and contract like railway tracks, leaving cracks similar to expansion joints. These cracks are also normal phenomena that occur during the normal use of the house due to environmental factor changes and do not threaten the structural safety of the house.
• Unidirectional Parallel Cracks: In older prefabricated slab houses, unidirectional cracks parallel to one side wall on the floor slab usually result from asynchronous deformation of the two prefabricated slabs. In cases where there is no significant deflection (i.e., no obvious bending or sinking of the floor slab), these cracks generally do not pose a safety hazard, although there may be a risk of water leakage.

Cases Requiring Caution

• Crack Characteristics: If a crack is wider than 0.3 millimeters and shows a tendency to widen continuously, or if an entire prefabricated slab is cracked from top to bottom, these are signals that require serious attention. Additionally, if cracks are accompanied by phenomena such as wall tilting or steel bar rusting, it indicates that the house may have relatively serious structural problems.
• Deformation Conditions: When the floor slab shows visible deflection or deformation, or when indoor cracks are continuous and wider than 0.7mm, it indicates that the structure of the house has been significantly affected and may pose a safety hazard. In such cases, it is essential to promptly contact a professional agency for inspection and carry out necessary reinforcement measures based on the inspection results to ensure the safe use of the house.