How Thick Should the Roof of a Prefabricated House Be

The common thicknesses of prefabricated house roofs (prefabricated floor slabs) are 120mm and 150mm, and in rural house construction, a 180mm specification may also be adopted. The specific thickness selection needs to be determined comprehensively based on safety, economy, construction convenience, and special requirements. The following is a detailed explanation:

Common Thickness Specifications

The thickness design of prefabricated floor slabs needs to meet structural mechanics requirements while taking into account material costs and construction efficiency. The 120mm thickness is the most commonly used specification in residential buildings, suitable for areas such as living rooms and bedrooms in ordinary residences. It can meet conventional load requirements and is highly economical. The 150mm thickness is mostly used in scenarios with larger spans or higher load requirements, such as public buildings, commercial spaces, or floors with heavy equipment. Its flexural rigidity is significantly improved, effectively reducing the risk of deformation. In rural house construction, 120mm, 150mm, and 180mm are mainstream choices, among which the 180mm specification is usually used in areas that require additional load-bearing capacity or pre-embedded complex pipelines, such as kitchens, bathrooms, or floors with underfloor heating systems.

Core Factors for Thickness Selection

1. Safety: The floor slab thickness needs to be determined based on design load calculations. For example, when the live load standard value (such as the weight of people and furniture) is 2.0kN/㎡, a 120mm thick prefabricated floor slab can meet the requirements; if the live load increases to 3.5kN/㎡ (such as in industrial plants), a 150mm or thicker specification is required. In addition, areas with high seismic fortification intensity need to appropriately increase the thickness to improve the overall structural integrity.
2. Economy: An increase in thickness directly leads to an increase in material consumption. Calculated based on concrete consumption, a 150mm floor slab is 25% thicker than a 120mm one, and the cost increases by about 15%-20% accordingly. Therefore, under the premise of meeting safety requirements, thinner specifications should be preferred to control costs.
3. Construction Convenience: Thinner floor slabs are lighter in weight, facilitating lifting and installation, especially suitable for rural house projects with manual construction or limited mechanical conditions. However, overly thin floor slabs (such as <100mm) may have a higher risk of transportation damage due to insufficient stiffness.
4. Special Requirements: If it is necessary to pre-embed large-diameter pipelines (such as drainage pipes with a diameter of DN100 or above) or lay underfloor heating systems, sufficient space needs to be reserved within the floor slab. In this case, a 180mm thickness may be required or a local thickening design may be adopted.

Regulatory Basis and Recommendations

According to the requirements of the Code for Design of Concrete Structures (GB50010), the minimum thickness of prefabricated floor slabs should not be less than 60mm, and they need to meet the requirements for reinforcement ratio and crack control. In actual projects, it is recommended to preferentially adopt the standard specifications of 120mm or 150mm for residential buildings. For rural house projects, selections can be made within the range of 120-180mm according to specific requirements, and it should be ensured that the design documents are reviewed and confirmed by professional structural engineers.