Prefabricated Slab Roof for Self-Built Houses

The use of prefabricated slabs for the roofs of self-built houses was once common in rural areas, but they have many drawbacks. If conditions permit, it is recommended to use cast-in-place roofs; when necessary, certain precautions should be taken.

Drawbacks of Prefabricated Slabs

• Structural Aspect: Prefabricated slabs are placed on both sides of the wall. Even with a ring beam poured, their overall integrity is inferior to that of a slab and ring beam cast together. The middle part of the slab does not bear weight, resulting in poor overall integrity. In earthquake-prone areas, their seismic resistance coefficient is low, making them prone to collapse.
• Waterproofing Aspect: There is a high probability of water leakage when applying waterproofing. Many rural self-built houses with prefabricated slab roofs experience water leakage, with some even saying that “8 out of 10 houses leak.” The waterproofing industry cannot guarantee 100% leak-proofing.
• Sound Insulation Aspect: The sound insulation effect is poor. Activities on the upper floor can be clearly heard on the lower floor.
• Thermal Insulation Aspect: The thermal insulation is poor. The indoor temperature is high in summer and low in winter. Generally, a secondary roofing material covering is required on the slab to compensate.
• Lifespan Aspect: The lifespan of prefabricated slabs is only 30 years.

Advantages of Prefabricated Slabs

They are inexpensive. For example, the price of a hollow prefabricated floor slab, a concrete load-bearing floor slab, a concrete prestressed cover slab, and a round-hole floor slab for house construction is approximately 36.0 yuan per meter. The price of a reinforced concrete hollow slab for factory and residential building roofs is approximately 24.0 yuan per meter.

Alternative Recommendations

If financial constraints are not a major issue, it is recommended to use a cast-in-place concrete roof. Cast-in-place roof slabs are sturdy, have strong seismic resistance, a wide range of applications, and good waterproofing. Although the construction process is complex, slow, and costly, the safety factor is higher.

Precautions for Using Prefabricated Slabs

If conditions are limited and prefabricated slabs must be used, it is important to purchase them from a reputable manufacturer to ensure that the specifications and quantity of internal steel bars comply with national standards and that there are no holes or cracks in the appearance. During construction, leave a gap between two prefabricated slabs and fill it with cement grout after installation to enhance adhesion. Do not cut slots or holes in the prefabricated slabs, and do not use them in areas with high waterproofing requirements, such as kitchens and bathrooms.