Cracking in the Roof of Prefabricated Slab Buildings

The causes of cracking in the roof of prefabricated slab buildings are diverse, and the treatment methods need to be targeted according to the age of the building and the specific causes.

Causes of Cracking

1. Temperature or shrinkage cracks: If the concrete is not watered and cured in a timely manner after pouring, the rapid evaporation of internal moisture will cause the concrete to shrink, resulting in shallow capillary cracks, which are relatively common quality issues.
2. Improper formwork removal time: If the formwork is removed before the concrete reaches the specified formwork removal strength, the concrete has not yet developed sufficient load-bearing capacity and is prone to cracking due to external forces.
3. Manual disturbance: To meet construction deadlines, developers may carry out subsequent construction work, such as stacking materials and personnel movement, before the concrete reaches the design strength. These disturbances can damage the internal structure of the concrete and form cracks.
4. Settlement cracks: Uneven foundation settlement is the cause of such cracks. Although the probability of occurrence is relatively low, once they appear, they are mostly structural cracks and will continue to worsen over time. They must be evaluated and treated by a specialized appraisal unit.
5. Issues with the prefabricated slabs themselves: In old houses, the top surfaces of the prefabricated slabs have a clear orientation, with large gaps between the slabs, which can be up to 4 centimeters wide. Additionally, the slabs are uneven, with height differences between two adjacent slabs. These factors can easily lead to through cracks.
6. Problems with the splicing process: Taking the 3D steel bar truss floor slab prefabricated construction process as an example, cracks are prone to appear at the splicing positions of the prefabricated bottom formwork. These cracks will lengthen and widen over time due to stress changes at the splicing points and insufficient bonding strength between the slabs.

Treatment Methods

1. Old houses: During the renovation of old houses, sufficient budget should be reserved to address roof issues. Since cracking in the roof of prefabricated slab buildings may lead to hollowing, posing a safety hazard of family members being hit by falling debris, timely treatment can avoid such risks.
2. New houses: Reference can be made to the practices of project departments similar to those in Liangshan County Shangchengfu. Rectification and compensation plans can be introduced, and property management companies can simultaneously offer property fee reductions as an option. Homeowners can negotiate with developers to resolve roof cracking issues through reasonable means.