Thickness of Floor Slabs in Prefabricated Slab Houses

The thickness of floor slabs in prefabricated slab houses is commonly 120mm or 150mm. The following provides an explanation from three aspects: specification standards, application scenarios, and basis for thickness selection:

Specification Standards and Typical Parameters

As a widely used floor slab form in early construction, the thickness design of prefabricated slabs needs to meet structural safety and functional requirements. According to the specification parameters of traditional prefabricated slabs (large slabs), 120mm and 150mm are the two most typical thickness specifications. This standard is determined based on a comprehensive consideration of building load calculations, material properties, and construction convenience, ensuring both the load-bearing capacity of the floor slab and economic efficiency and construction speed. For example, in ordinary residential buildings, a 120mm-thick prefabricated slab can meet the daily living load requirements; while in industrial plants or commercial buildings, due to the larger equipment loads or higher foot traffic, the application of 150mm-thick prefabricated slabs is more common.

Application Scenarios and Thickness Adaptation

Different building types have varying requirements for floor slab thickness. 120mm-thick prefabricated slabs are mostly used in low-rise residential buildings, dormitories, and other scenarios with relatively small loads. Their lighter weight can reduce the foundation load and lower material costs. 150mm-thick prefabricated slabs are suitable for multi-story residential buildings, office buildings, or light industrial buildings. Their higher section modulus can effectively resist bending moments and enhance the overall structural stiffness. In addition, if the building requires the installation of additional layers such as underfloor heating or tiles, or if there are vibrating equipment (such as elevator machine rooms), a thickness of 150mm can provide more sufficient load-bearing capacity.

Basis for Thickness Selection

The determination of floor slab thickness requires a comprehensive consideration of multiple factors:

1. Load requirements: According to the "Building Structural Load Code", the standard value of live load on residential floors is 2.0kN/㎡, and it may reach over 3.5kN/㎡ in industrial buildings. An increase in thickness can significantly enhance the bending resistance of the floor slab. For example, the bending stiffness of a 150mm slab is about 56% higher than that of a 120mm slab.
2. Span limitations: The span of prefabricated slabs is usually 3-6m. As the span increases, the thickness needs to be increased accordingly to control deflection. For example, with a 6m span, the deflection of a 150mm slab can be controlled within L/250 (24mm), meeting comfort requirements.
3. Durability requirements: Thicker slabs can reduce the depth of concrete carbonation and delay steel bar corrosion, making them especially suitable for humid environments or highly corrosive locations.
4. Construction conditions: Thicker slabs require larger equipment for transportation and hoisting, while thinner slabs have higher requirements for construction accuracy. The choice needs to be balanced according to on-site conditions.

It should be noted that prefabricated slabs have gradually been replaced by cast-in-place concrete floor slabs in modern construction, but they still have application value in the renovation of existing buildings or specific scenarios. During the design process, it is necessary to combine specific codes and engineering realities to ensure that the thickness selection is scientific and reasonable.