Prefabricated Floor Slab in House Structure
The prefabricated floor slab in house structures is a commonly used floor component in early 20th-century buildings, referring to a concrete prefabricated part produced and processed at a prefabrication site and directly transported to the construction site for installation.
I. Production Process During production, a hollow mold is first made by nailing wooden boards. After placing steel bars in the hollow part of the mold, cement is poured to fill the hollow part. After it dries, the wooden boards are knocked off to obtain the prefabricated slab. Prefabricated slabs are divided into two types: solid and hollow. The hollow structure achieves lightweighting by reducing the non-load-bearing concrete.
II. Dimensions and Loads For residential prefabricated slabs, the maximum span is 4.2 meters, with widths of 500mm and 600mm being more common, and thicknesses of 120mm and 150mm being typical. In terms of live load ratings, Grade I slabs (capable of bearing 1kN/m²) and Grade II slabs (capable of bearing 2kN/m²) are generally used in residential buildings, while the minimum requirement in the southwest region is Grade IV slabs (capable of bearing 4kN/m²). The lengths are generally based on a modulus of 300mm, such as 3000, 3300, etc., with the longest ordinary slab being 4200.
III. Application History and Structural Forms Prefabricated slab houses originated in the early 20th century. In China, residential buildings constructed before 1985 often adopted this type of structure, and prefabricated slab buildings were commonly seen in urban residential areas from the 1970s to the 1990s. Floor slabs, some walls, or other components are prefabricated in factories and then assembled on-site. The walls are mostly made of brick or prefabricated concrete wall panels, and the structural form is mainly brick-concrete structure. With its fast construction speed and low cost, it was widely used in the construction of affordable housing and economic housing at that time.
IV. Existing Problems and Renovation Policies Existing prefabricated slab houses generally have problems such as weak earthquake resistance, poor sound and heat insulation, and a service life of about 30 - 50 years. With the development of building technology, cast-in-place concrete and prefabricated buildings are gradually replacing traditional prefabricated slab houses. Since 2022, China has implemented a policy of renovating old buildings, focusing on repairing and renovating prefabricated slab houses and only demolishing buildings that meet the criteria for dangerous buildings. Some regions have already carried out demolition work. In 2024, it was found that 26.3% of old buildings underwent reinforcement and renovation, which is divided into four levels: painting for usable ones, adding steel bars for dangerous ones, and direct demolition for those that are truly beyond repair.
