Prefabricated Slab Roof Design

Prefabricated slab roof design was once used in rural self-built houses, but it has many problems. Nowadays, its application is gradually decreasing, and there are new improvement methods.

Structural Characteristics

Prefabricated slabs are pre-made components. Their materials include crushed stone, cement, sand, and coiled wire (or cold-drawn wire), which differ from the materials used for cast-in-place concrete roofs. Prefabricated slabs do not form an integral whole with the roof but are directly placed on brick walls. This structure prevents them from providing tensile and stabilizing effects.

Advantages

The biggest advantage of prefabricated slabs is their low cost. The construction cost is relatively low, making them attractive for some rural self-built houses with limited budgets.

Disadvantages

• Difficulty in Solving Leakage Problems: Waterproofing is a significant issue for prefabricated slab roofs. Usually, waterproof materials are laid, and asphalt is used to fill gaps for waterproofing. However, due to temperature changes, cracks can appear between the waterproof materials and the roof surface, leading to leaks. Although their designed service life can reach 30 years and they remain safe for up to 50 years, leakage is a common problem. The roof may not leak for 3 - 5 years after construction, but leakage will gradually increase thereafter, and there is no good solution. Waterproofing treatments are not only costly but also cannot guarantee long-term leak prevention.
• Poor Earthquake Resistance: The seismic coefficient of prefabricated slabs is low. When the house has no ring beams, in the event of an earthquake, the slabs placed on the walls may collapse, causing harm to people.
• Poor Integrity: After being installed on the roof, prefabricated slabs are independent pieces connected with concrete or cement mortar in the middle, not forming an integral whole. As the house ages, the foundation may settle, causing the slabs above to move and form cracks. This not only leads to leaks but also causes concerns.

Application Scenarios

Nowadays, reinforced concrete integrated cast roofs are basically used for rural house construction. These roofs perform well in terms of waterproofing, load-bearing, and thermal insulation. To solve the leakage problem of prefabricated slab roofs, it is popular in rural areas to build triangular roofs with color steel plates on the original roofs, which can basically ensure no leaks for more than 10 years and are also affordable. However, there are also cases where prefabricated slabs are used for pitched roofs. For example, in a one-and-a-half-story house, five-hole prefabricated slabs are placed on the pitched roof, and a horizontal component is made at the end to prevent sliding.