Cracks and Rain Leakage in Prefabricated Floor Slab Houses

The main causes of cracks and rain leakage in prefabricated floor slab houses are defects in the joint treatment of prefabricated slabs, weak waterproof layers, and material aging. These issues can be addressed through emergency repairs or targeted crack treatment solutions.

Causes of Cracks and Rain Leakage

1. Defects in the Joint Treatment of Prefabricated Slabs: Prefabricated slabs are connected through grouting or welding. However, thermal expansion and contraction caused by earthquakes and temperature changes can easily lead to joint cracking, allowing rainwater to seep in along the cracks. For example, the Hefei Sanxiaokou Qiguitang Community once experienced rainwater flowing within the prefabricated slabs, which was difficult to completely repair.
2. Weak Waterproof Layers: The construction quality of the waterproof layers on the roofs of prefabricated slab houses is generally poor. About 80% of rural self-built houses have rain leakage problems. Even after multiple repairs, they are still prone to failure. The root cause lies in defects in the waterproof layer materials or construction techniques.
3. Material Aging: The materials of prefabricated slabs age quickly, with a typical service life of only about 10 years. After aging, the structural strength decreases, cracks increase, and rain leakage problems become more severe during heavy rain.

Emergency Treatment Solutions

1. Color Steel Roof Covering: This provides the best overall waterproofing effect but has a relatively high cost, approximately 60 - 80 yuan per square meter, and is suitable for long-term use requirements.
2. Waterproof Membrane Repair: This depends on the construction quality and has a lifespan of about 15 years. However, there is a risk of repair failure, so a professional construction team should be selected.
3. Plastic Film Covering: This has the lowest cost, only 2 yuan per square meter, but the effect only lasts for 2 - 3 years. It is suitable for temporary emergency situations or when the budget is limited.

Targeted Treatment for Crack Leakage

1. Surface Repair Method: Suitable for narrow cracks. After cleaning the floor slab surface, lay a film material along the crack with a brush. Apply epoxy resin or resin impregnation every 3 - 5 minutes, with a coating thickness of about 1 millimeter. Finally, smooth the surface with 1:2 cement mortar.
2. Injection Method: For fine and deep cracks. After cleaning the surface, cut the crack into a V-shaped groove. Pour C30 fine aggregate concrete mixed with 2 - 5% cement mortar, asphalt, or resin mortar. Arrange steel bars in both directions along the floor slab and cure them.
3. Pouring and Filling Method: Suitable for wider cracks. After cleaning the surface, cut a 5 - 8mm V-shaped groove. Arrange steel bars (embedded 5 centimeters into the wall) and pour C30 fine aggregate concrete onto the floor slab with a thickness of about 5 centimeters.

Preventive Measures (Suggestions for Rural House Construction)

For cast-in-place floor slabs, attention should be paid to the following: preventing foundation settlement, tightly sealing the joints of formwork, arranging steel bars in a double-layer and bidirectional manner, ensuring the thickness of the protective layer meets the standards, adding radial bars at the external corners, dispersing pre-embedded pipelines, and prohibiting the random addition of water to the concrete to reduce the risk of cracks.