Precast Slabs for Self-Built Houses

If precast slabs must be used in rural self-built houses, it is essential to strictly adhere to the following specifications and fully understand their drawbacks:

Drawbacks of Precast Slabs

1. Poor Seismic Performance: The connection methods between precast slabs are prone to damage under external forces such as earthquakes, leading to detachment or overall structural instability. Their use is strictly prohibited in earthquake-prone areas.
2. Prominent Waterproofing Issues: Even with waterproofing measures, the probability of rain leakage remains as high as 80%. The joints between slabs are prone to widening over time, resulting in leakage.
3. Poor Thermal Insulation: The floor slab is approximately 12 centimeters thick (hollow structure), leading to high indoor temperatures in summer and low temperatures in winter, necessitating additional thermal insulation materials.
4. Short Service Life: Manufacturers claim a lifespan of 50 years, but in reality, issues such as aging, cracking, and leakage often appear after about 10 years.
5. Prone to Cracking: Due to size limitations, the overall structural integrity of the floor slab is poor, and the joints are prone to widen due to deformation, causing water leakage.
6. Poor Sound Insulation: Sounds from activities upstairs are clearly audible, affecting living comfort.

Construction Specifications and Precautions

1. Material Selection:

   • Purchase precast slabs produced by reputable large manufacturers, using prestressed steel bars and concrete with a strength not lower than C30. The specifications and quantity of steel bars must comply with national standards.
   • Visual inspection: Ensure there are no cracks, honeycombs, holes, or other defects.

2. Installation Requirements:

   • When placed on concrete members, the length should be ≥80mm; when placed on walls, the length should be ≥100mm.
   • When installing, leave a 20-40mm gap between two slabs. Apply mortar at the bottom ends of the slabs, and fill the holes at both ends of the slabs on the wall with concrete.

3. Usage Restrictions:

   • Do not arbitrarily cut holes or slots. Precast slabs are prohibited in kitchens and bathrooms (due to waterproofing and load-bearing requirements).

4. Joint Treatment:

   • After cleaning debris from the joints, pour cement mortar and vibrate it densely. For larger joints, pour concrete and cure it; using bricks to fill is strictly prohibited.

5. Roof Waterproofing:

   • Preferably use a cast-in-place roof. If precast slabs are used, first arrange a steel bar mesh and then pour 6-8mm thick crushed stone concrete.

Safety Recommendations

From the perspective of building safety, cast-in-place slabs are a better choice. The state has explicitly prohibited the use of precast slabs in commercial housing construction (e.g., implemented in Jining City in 2012 and Sichuan Province in 2005). Although there is no mandatory regulation for rural self-built houses, in the long run, cast-in-place slabs offer significant advantages in terms of seismic resistance, waterproofing, and durability.