What to Do If a Prefabricated House Cracks

For cracks in a prefabricated house, targeted treatment measures should be taken based on the crack conditions, as follows:

1. Observe the crack conditions and determine whether repair is needed

If there are few cracks, the gaps are small (usually less than 0.2 millimeters in width), and there is no liquid leakage or structural deformation on the floor, repair can be temporarily postponed. Such cracks are mostly surface micro-cracks caused by concrete shrinkage or temperature changes, having a relatively small impact on the overall structural safety of the house. However, it is necessary to regularly observe whether the cracks expand.

2. Immediately repair larger cracks to prevent leakage or structural damage

If the crack width exceeds 0.2 millimeters or there is liquid leakage (such as rainwater infiltration or pipeline leakage), immediate repair is required. The specific steps are as follows:

1. Chisel out the cracks: Chisel out the board seams where the cracks are located. Chisel away 5 centimeters from each side of the surface layer to make the joint surface slope-shaped. Also, appropriately chisel the surface of the prefabricated floor slab and the side of the slab to enhance the bonding strength between the new and old concrete.
2. Clean the base layer: Use a high-pressure water gun or a brush to clean the chiseled board seams to ensure there is no dust, oil, or loose particles.
3. Apply cement mortar: Apply a layer of pure cement mortar inside the board seams, with a water-cement ratio controlled between 0.4 and 0.5, to seal the base layer and enhance the bonding property.
4. Pour fine aggregate concrete:
   • Pour for the first time to half of the depth of the board seams. After the fine aggregate concrete absorbs water for a moment, pour for the second time.
   • Pour for the second time to 1 centimeter from the floor surface. Compact and level it with a vibrating rod to ensure the concrete is dense and free of voids.
5. Curing: After the repair is completed, cover with plastic film or wet burlap for curing for at least 2-3 days. During this period, stepping or stacking heavy objects is strictly prohibited to prevent concrete cracking.

3. Post-repair reinforcement treatment to improve crack resistance

After the crack repair, the following methods can be used for further reinforcement:

1. Fill the gaps: Fill the inside of the cracks with epoxy resin putty or elastic sealant to ensure the gaps are completely dense.
2. Paste reinforcing materials: Paste Dacron cloth or mesh cloth on the crack surface, and then cover with carbon fiber cloth. Enhance the overall structural integrity through the high-strength characteristics of the fibers to prevent the cracks from expanding again.

Precautions: If the cracks continue to expand, multiple parallel cracks appear, or there is structural abnormal noise, it may involve loose connections of prefabricated components or foundation settlement. Immediately contact a professional organization for inspection and avoid self-handling to prevent safety hazards.