Prefabricated Slab Roof
The prefabricated slab roof is characterized by complex structural properties, prominent waterproofing issues, poor thermal insulation, low construction costs but requiring independent waterproofing, and standardized renovation solutions.
In terms of structural properties: The prefabricated slab roof is assembled by splicing multiple prefabricated concrete slabs. There are natural splicing gaps between the slabs, resulting in relatively weak overall structural integrity. The spliced structure makes the slab joints the core water infiltration channels. Over time, affected by temperature-induced expansion and contraction, building settlement, and slight roof loads, the slab joints will continuously open and close, causing ordinary waterproofing materials to be easily cracked and delaminated. The surface of the prefabricated slabs is prone to problems such as unevenness, sanding, peeling, and fine honeycomb cracks. The基层 (sub-base) diseases are scattered and complex. Rainwater can freely flow under the waterproof layer along the slab joints and sub-base gaps, resulting in hidden leakage phenomena where the leakage points do not correspond to the water infiltration points. Local repairs cannot provide a radical solution. Seasonal temperature variations cause continuous thermal expansion and contraction of the prefabricated slabs, with frequent dynamic displacement of the slab joints. Ordinary thin-layer waterproof coatings and non-standard membranes have insufficient tensile and deformation resistance, making them prone to cracking and failure in the short term. The re-leakage rate is much higher than that of cast-in-place roofs. The roof gutters are areas where water, dust, and fallen leaves accumulate. They are constantly exposed to rainwater scouring and ultraviolet radiation. Conventional waterproofing materials are prone to aging, pulverization, and peeling, making them the most vulnerable nodes for leakage.
In terms of waterproofing issues: Gradual cracking of the original roof sub-base gaps, loosening and sanding of the leveling layer, and aging and failure of the old waterproof layer can lead to stubborn leakage problems such as full-roof water infiltration, dampness and mold on the interior walls of the top floor, peeling of the ceiling, and water accumulation and channeling in the gutters. In rural self-built houses, when prefabricated slabs are used for the roof, the probability of rain leakage during waterproofing is high.
In terms of thermal insulation issues: The prefabricated floor slabs used in rural self-built houses are generally about 12 centimeters thick, resulting in poor thermal insulation. The indoor temperature is high in summer and low in winter. Generally, a secondary roofing material coverage is required on the floor slabs to make up for this deficiency.
In terms of construction and costs: Prefabricated slabs are cement components prefabricated in factories. They are formed by nailing wooden models, laying out steel bars, and pouring cement during production. They are divided into two types: solid and hollow. The hollow structure achieves lightweighting by reducing the non-load-bearing concrete. In rural self-built houses, prefabricated cement slabs are inexpensive and have a fast construction speed, but independent waterproofing is required.
In terms of renovation and policies: 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 houses. For common industry problems, standardized and meticulous construction processes can be adopted for renovation.
