Dimensions and Load-Bearing Capacity of House Prefabricated Slabs

The common dimensions of house prefabricated slabs are a maximum span of 4.2 meters (for residential use), with widths mostly being 500mm or 600mm, and thicknesses commonly at 120mm and 150mm. The load-bearing capacity varies significantly depending on factors such as type, span, and reinforcement, with a range of 100 kilograms to over 400 kilograms per square meter.

I. Load-Bearing Capacity by Type

1. Concrete Hollow Slabs: The national standard for uniformly distributed load is 200-250 kilograms per square meter. For example, a hollow slab measuring 3.6 meters in length and 0.6 meters in width (with an area of 2.16 square meters) has a total load-bearing capacity of 2.16×200=432 kilograms, allowing for the even placement of 8 bags of 50-kilogram cement. However, concentrated loads should be avoided to prevent cracking of the slab.
2. Solid Prefabricated Slabs: These have a higher load-bearing capacity than hollow slabs, reaching up to 250-300 kilograms per square meter. Solid slabs produced by large factories (with sufficient reinforcement and a concrete grade of C30 or higher) can bear up to 300 kilograms per square meter, supporting the weight of a 200-kilogram bathtub plus occupants.
3. Prestressed Prefabricated Slabs: These are reinforced with high-strength steel wires to generate prestress, enhancing their crack resistance and load-bearing capacity. For spans within 3 meters, the load-bearing capacity is 300-400 kilograms per square meter; for spans over 4 meters, it is 250-300 kilograms per square meter, which is 20% higher than that of ordinary slabs of the same span.
4. Classification by Grade: Grade I slabs have a standard value of 100 kilograms per square meter, suitable for placing lightweight items (such as furniture and for occupant movement); Grade IV slabs can bear over 400 kilograms per square meter, used in heavy-load scenarios like gyms and factories; when using laminated slab technology, the load-bearing capacity can be further increased by 30%.

II. Key Factors Affecting Load-Bearing Capacity

1. Span: A shorter span results in stronger load-bearing capacity. For example, a hollow slab with a 2.4-meter span can bear 250 kilograms per square meter, while a 3.6-meter span reduces this to 200 kilograms, and spans over 4.2 meters may only support 150-180 kilograms per square meter.
2. Thickness and Reinforcement: Increasing the thickness (e.g., from 8cm to 10cm) or enhancing the steel bar density (e.g., using 8mm steel bars with a spacing of 15cm) can significantly improve the load-bearing capacity. When purchasing, pay attention to the 'steel content' and 'concrete grade' specified in the instructions, with higher values indicating greater reliability.
3. Load Type: Uniformly distributed loads (such as sand) have less impact on the slab, while concentrated loads (e.g., placing a 300-kilogram safe within 1 square meter) can cause slab cracking and should be strictly avoided.

In practical applications, it is essential to select the appropriate type of prefabricated slab based on the specific scenario and ensure even load distribution to avoid overloading or concentrated forces.