Precast Slabs for Rural Self-Built Houses

The use of precast slabs in rural self-built houses presents various issues related to structural safety, leakage, sound insulation, lifespan, and earthquake resistance, necessitating careful selection and attention to size specifications and usage norms.

I. Main Disadvantages

1. High Structural Safety Risks: Precast slabs are only connected to walls at both ends. Even with the pouring of a ring beam, their overall stability is far inferior to that of cast-in-place floor slabs. Slight shaking or external impact can cause slab detachment, especially during disasters like earthquakes, where precast slab structures are prone to complete collapse, posing a fatal risk. Currently, precast slabs are completely banned in commercial housing, and self-built houses also require strict safety assessments.
2. Prominent Leakage Problems: The gaps at the joints of precast slabs are high-risk areas for leakage, with waterproofing performance far inferior to that of cast-in-place slabs. In water-using areas such as kitchens and bathrooms, the use of precast slabs can easily lead to wall moisture and ceiling dripping due to gap cracking in the later stages, with high repair costs and difficulty in achieving a permanent solution.
3. Poor Sound Insulation: Precast slabs have a hollow or lightweight internal structure, resulting in weak sound-blocking capabilities. Noise from upstairs, such as footsteps and furniture movement, can be clearly heard downstairs, affecting living comfort.
4. Short Service Life: Precast slabs are typically designed for a lifespan of about 30 years, but in actual use, they may develop cracks and deformations within about 10 years due to material aging and overloading, requiring frequent repairs or replacement.
5. Weak Earthquake Resistance: Precast slabs are connected to walls in a separated manner, making them prone to slab displacement or falling due to connection failure during earthquakes. Their earthquake resistance is significantly lower than that of cast-in-place structures, posing a particularly high risk in earthquake-prone areas.

II. Size Specifications and Selection Recommendations

1. Length: Common specifications range from 3 meters to 4.2 meters, increasing by 30 centimeters per increment. Precast slabs exceeding 4.2 meters in length pose high transportation risks and are prone to breakage, so customization is not recommended.
2. Width: The standard width is 50 centimeters or 60 centimeters, and it should be selected according to the room layout to avoid excessive jointing, which increases the risk of leakage.
3. Thickness: For ordinary rooms, a thickness of 12 centimeters can meet basic needs, but for the second floor or areas where heavy objects (such as furniture and equipment) need to be stacked, the thickness should be ≥15 centimeters to enhance load-bearing capacity.
4. Purchase Principles: Avoid selecting slabs that are too thin (e.g., less than 10 centimeters), do not believe merchants' claims of being able to customize lengths at will, and prioritize standard-specification products produced by regular manufacturers.

III. Usage Precautions If precast slabs must be used, the following principles should be strictly followed:

1. Strengthen Structural Connections: Add steel bar anchors at the slab joints and pour high-strength concrete ring beams to enhance overall stability.
2. Waterproofing in Key Areas: In areas such as kitchens and bathrooms, waterproofing membranes should be laid at the slab joints, and a closed-water test should be conducted to ensure no leakage before proceeding with subsequent construction.
3. Control Load: Avoid stacking heavy objects or conducting large-scale renovations on precast slab floors to prevent overloading and slab cracking.
4. Regular Inspection and Maintenance: Inspect the slab joints and wall connections for cracks every 5 years, and promptly repair cracks and reapply waterproofing treatments.